Bot-S: The Complete Works of Aristotle

The just, then, is the lawful and
the fair, the unjust the unlawful and the unfair.

Since the unjust man is grasping, he must be concerned with goods-not all goods, but those with which
prosperity and adversity have to do, which taken absolutely are always good, but for a particular person are
not always good. Now men pray for and pursue these things; but they should not, but should pray that the
things that are good absolutely may also be good for them, and should choose the things that are good for
them. The unjust man does not always choose the greater, but also the less-in the case of things bad
absolutely; but because the lesser evil is itself thought to be in a sense good, and graspingness is directed at
the good, therefore he is thought to be grasping. And he is unfair; for this contains and is common to both.

Since the lawless man was seen to be unjust and the law-abiding man just, evidently all lawful acts are in a
sense just acts; for the acts laid down by the legislative art are lawful, and each of these, we say, is just. Now
the laws in their enactments on all subjects aim at the common advantage either of all or of the best or of
those who hold power, or something of the sort; so that in one sense we call those acts just that tend to
produce and preserve happiness and its components for the political society. And the law bids us do both the
acts of a brave man (e.g. not to desert our post nor take to flight nor throw away our arms), and those of a
temperate man (e.g. not to commit adultery nor to gratify one's lust), and those of a good-tempered man (e.g.

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not to strike another nor to speak evil), and similarly with regard to the other virtues and forms of
wickedness, commanding some acts and forbidding others; and the rightly-framed law does this rightly, and
the hastily conceived one less well. This form of justice, then, is complete virtue, but not absolutely, but in
relation to our neighbour. And therefore justice is often thought to be the greatest of virtues, and 'neither
evening nor morning star' is so wonderful; and proverbially 'injustice is every virtue comprehended'. And it
is complete virtue in its fullest sense, because it is the actual exercise of complete virtue. It is complete
because he who possesses it can exercise his virtue not only in himself but towards his neighbour also; for
many men can exercise virtue in their own affairs, but not in their relations to their neighbour. This is why the
saying of Bias is thought to be true, that 'rule will show the man'; for a ruler is necessarily in relation to other
men and a member of a society. For this same reason justice, alone of the virtues, is thought to be 'another's
good', because it is related to our neighbour; for it does what is advantageous to another, either a ruler or a
copartner. Now the worst man is he who exercises his wickedness both towards himself and towards his
friends, and the best man is not he who exercises his virtue towards himself but he who exercises it towards
another; for this is a difficult task. Justice in this sense, then, is not part of virtue but virtue entire, nor is the
contrary injustice a part of vice but vice entire. What the difference is between virtue and justice in this sense
is plain from what we have said; they are the same but their essence is not the same; what, as a relation to
one's neighbour, is justice is, as a certain kind of state without qualification, virtue.

But at all events what we are investigating is the justice which is a part of virtue; for there is a justice of this
kind, as we maintain. Similarly it is with injustice in the particular sense that we are concerned.

That there is such a thing is indicated by the fact that while the man who exhibits in action the other forms of
wickedness acts wrongly indeed, but not graspingly (e.g. the man who throws away his shield through
cowardice or speaks harshly through bad temper or fails to help a friend with money through meanness),
when a man acts graspingly he often exhibits none of these vices,-no, nor all together, but certainly
wickedness of some kind (for we blame him) and injustice. There is, then, another kind of injustice which is a
part of injustice in the wide sense, and a use of the word 'unjust' which answers to a part of what is unjust in
the wide sense of 'contrary to the law'. Again if one man commits adultery for the sake of gain and makes
money by it, while another does so at the bidding of appetite though he loses money and is penalized for it,
the latter would be held to be self-indulgent rather than grasping, but the former is unjust, but not
self-indulgent; evidently, therefore, he is unjust by reason of his making gain by his act. Again, all other
unjust acts are ascribed invariably to some particular kind of wickedness, e.g. adultery to self-indulgence, the
desertion of a comrade in battle to cowardice, physical violence to anger; but if a man makes gain, his action
is ascribed to no form of wickedness but injustice. Evidently, therefore, there is apart from injustice in the
wide sense another, 'particular', injustice which shares the name and nature of the first, because its definition
falls within the same genus; for the significance of both consists in a relation to one's neighbour, but the one
is concerned with honour or money or safety-or that which includes all these, if we had a single name for
it-and its motive is the pleasure that arises from gain; while the other is concerned with all the objects with
which the good man is concerned.

It is clear, then, that there is more than one kind of justice, and that there is one which is distinct from virtue
entire; we must try to grasp its genus and differentia.

The unjust has been divided into the unlawful and the unfair, and the just into the lawful and the fair. To the
unlawful answers the afore-mentioned sense of injustice. But since unfair and the unlawful are not the same,
but are different as a part is from its whole (for all that is unfair is unlawful, but not all that is unlawful is
unfair), the unjust and injustice in the sense of the unfair are not the same as but different from the former
kind, as part from whole; for injustice in this sense is a part of injustice in the wide sense, and similarly
justice in the one sense of justice in the other. Therefore we must speak also about particular justice and
particular and similarly about the just and the unjust. The justice, then, which answers to the whole of virtue,
and the corresponding injustice, one being the exercise of virtue as a whole, and the other that of vice as a

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whole, towards one's neighbour, we may leave on one side. And how the meanings of 'just' and 'unjust' which
answer to these are to be distinguished is evident; for practically the majority of the acts commanded by the
law are those which are prescribed from the point of view of virtue taken as a whole; for the law bids us
practise every virtue and forbids us to practise any vice. And the things that tend to produce virtue taken as a
whole are those of the acts prescribed by the law which have been prescribed with a view to education for the
common good. But with regard to the education of the individual as such, which makes him without
qualification a good man, we must determine later whether this is the function of the political art or of
another; for perhaps it is not the same to be a good man and a good citizen of any state taken at random.

Of particular justice and that which is just in the corresponding sense, (A) one kind is that which is
manifested in distributions of honour or money or the other things that fall to be divided among those who
have a share in the constitution (for in these it is possible for one man to have a share either unequal or equal
to that of another), and (B) one is that which plays a rectifying part in transactions between man and man. Of
this there are two divisions; of transactions (1) some are voluntary and (2) others involuntary- voluntary such
transactions as sale, purchase, loan for consumption, pledging, loan for use, depositing, letting (they are
called voluntary because the origin of these transactions is voluntary), while of the involuntary (a) some are
clandestine, such as theft, adultery, poisoning, procuring, enticement of slaves, assassination, false witness,
and (b) others are violent, such as assault, imprisonment, murder, robbery with violence, mutilation, abuse,
insult.

(A) We have shown that both the unjust man and the unjust act are unfair or unequal; now it is clear that there
is also an intermediate between the two unequals involved in either case. And this is the equal; for in any kind
of action in which there's a more and a less there is also what is equal. If, then, the unjust is unequal, just is
equal, as all men suppose it to be, even apart from argument. And since the equal is intermediate, the just will
be an intermediate. Now equality implies at least two things. The just, then, must be both intermediate and
equal and relative (i.e. for certain persons). And since the equall intermediate it must be between certain
things (which are respectively greater and less); equal, it involves two things; qua just, it is for certain people.
The just, therefore, involves at least four terms; for the persons for whom it is in fact just are two, and the
things in which it is manifested, the objects distributed, are two. And the same equality will exist between the
persons and between the things concerned; for as the latter the things concerned-are related, so are the
former; if they are not equal, they will not have what is equal, but this is the origin of quarrels and
complaints-when either equals have and are awarded unequal shares, or unequals equal shares. Further, this
is plain from the fact that awards should be 'according to merit'; for all men agree that what is just in
distribution must be according to merit in some sense, though they do not all specify the same sort of merit,
but democrats identify it with the status of freeman, supporters of oligarchy with wealth (or with noble birth),
and supporters of aristocracy with excellence.

The just, then, is a species of the proportionate (proportion being not a property only of the kind of number
which consists of abstract units, but of number in general). For proportion is equality of ratios, and involves
four terms at least (that discrete proportion involves four terms is plain, but so does continuous proportion,
for it uses one term as two and mentions it twice; e.g. 'as the line A is to the line B, so is the line B to the line
C; the line B, then, has been mentioned twice, so that if the line B be assumed twice, the proportional terms
will be four); and the just, too, involves at least four terms, and the ratio between one pair is the same as that
between the other pair; for there is a similar distinction between the persons and between the things. As the
term A, then, is to B, so will C be to D, and therefore, alternando, as A is to C, B will be to D. Therefore also
the whole is in the same ratio to the whole; and this coupling the distribution effects, and, if the terms are so
combined, effects justly. The conjunction, then, of the term A with C and of B with D is what is just in
distribution, and this species of the just is intermediate, and the unjust is what violates the proportion; for the
proportional is intermediate, and the just is proportional. (Mathematicians call this kind of proportion
geometrical; for it is in geometrical proportion that it follows that the whole is to the whole as either part is to
the corresponding part.) This proportion is not continuous; for we cannot get a single term standing for a

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person and a thing.

This, then, is what the just is-the proportional; the unjust is what violates the proportion. Hence one term
becomes too great, the other too small, as indeed happens in practice; for the man who acts unjustly has too
much, and the man who is unjustly treated too little, of what is good. In the case of evil the reverse is true; for
the lesser evil is reckoned a good in comparison with the greater evil, since the lesser evil is rather to be
chosen than the greater, and what is worthy of choice is good, and what is worthier of choice a greater good.

This, then, is one species of the just.

(B) The remaining one is the rectificatory, which arises in connexion with transactions both voluntary and
involuntary. This form of the just has a different specific character from the former. For the justice which
distributes common possessions is always in accordance with the kind of proportion mentioned above (for in
the case also in which the distribution is made from the common funds of a partnership it will be according to
the same ratio which the funds put into the business by the partners bear to one another); and the injustice
opposed to this kind of justice is that which violates the proportion. But the justice in transactions between
man and man is a sort of equality indeed, and the injustice a sort of inequality; not according to that kind of
proportion, however, but according to arithmetical proportion. For it makes no difference whether a good
man has defrauded a bad man or a bad man a good one, nor whether it is a good or a bad man that has
committed adultery; the law looks only to the distinctive character of the injury, and treats the parties as
equal, if one is in the wrong and the other is being wronged, and if one inflicted injury and the other has
received it. Therefore, this kind of injustice being an inequality, the judge tries to equalize it; for in the case
also in which one has received and the other has inflicted a wound, or one has slain and the other been slain,
the suffering and the action have been unequally distributed; but the judge tries to equalize by means of the
penalty, taking away from the gain of the assailant. For the term 'gain' is applied generally to such cases, even
if it be not a term appropriate to certain cases, e.g. to the person who inflicts a woundand 'loss' to the sufferer;
at all events when the suffering has been estimated, the one is called loss and the other gain. Therefore the
equal is intermediate between the greater and the less, but the gain and the loss are respectively greater and
less in contrary ways; more of the good and less of the evil are gain, and the contrary is loss; intermediate
between them is, as we saw, equal, which we say is just; therefore corrective justice will be the intermediate
between loss and gain. This is why, when people dispute, they take refuge in the judge; and to go to the judge
is to go to justice; for the nature of the judge is to be a sort of animate justice; and they seek the judge as an
intermediate, and in some states they call judges mediators, on the assumption that if they get what is
intermediate they will get what is just. The just, then, is an intermediate, since the judge is so. Now the judge
restores equality; it is as though there were a line divided into unequal parts, and he took away that by which
the greater segment exceeds the half, and added it to the smaller segment. And when the whole has been
equally divided, then they say they have 'their own'-i.e. when they have got what is equal. The equal is
intermediate between the greater and the lesser line according to arithmetical proportion. It is for this reason
also that it is called just (sikaion), because it is a division into two equal parts (sicha), just as if one were to
call it sichaion; and the judge (sikastes) is one who bisects (sichastes). For when something is subtracted from
one of two equals and added to the other, the other is in excess by these two; since if what was taken from the
one had not been added to the other, the latter would have been in excess by one only. It therefore exceeds the
intermediate by one, and the intermediate exceeds by one that from which something was taken. By this,
then, we shall recognize both what we must subtract from that which has more, and what we must add to that
which has less; we must add to the latter that by which the intermediate exceeds it, and subtract from the
greatest that by which it exceeds the intermediate. Let the lines AA', BB', CC be equal to one another; from
the line AA' let the segment AE have been subtracted, and to the line CC let the segment CD have been
added, so that the whole line DCC exceeds the line EA' by the segment CD and the segment CF; therefore it
exceeds the line BB' by the segment CD. (See diagram.)

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These names, both loss and gain, have come from voluntary exchange; for to have more than one's own is
called gaining, and to have less than one's original share is called losing, e.g. in buying and selling and in all
other matters in which the law has left people free to make their own terms; but when they get neither more
nor less but just what belongs to themselves, they say that they have their own and that they neither lose nor
gain.

Therefore the just is intermediate between a sort of gain and a sort of loss, viz. those which are involuntary; it
consists in having an equal amount before and after the transaction.

Some think that reciprocity is without qualification just, as the Pythagoreans said; for they defined justice
without qualification as reciprocity. Now 'reciprocity' fits neither distributive nor rectificatory justice-yet
people want even the justice of Rhadamanthus to mean this:

Should a man suffer what he did, right justice would be done -for in many cases reciprocity and rectificatory
justice are not in accord; e.g. (1) if an official has inflicted a wound, he should not be wounded in return, and
if some one has wounded an official, he ought not to be wounded only but punished in addition. Further (2)
there is a great difference between a voluntary and an involuntary act. But in associations for exchange this
sort of justice does hold men together-reciprocity in accordance with a proportion and not on the basis of
precisely equal return. For it is by proportionate requital that the city holds together. Men seek to return either
evil for evil-and if they cana not do so, think their position mere slavery-or good for good-and if they
cannot do so there is no exchange, but it is by exchange that they hold together. This is why they give a
prominent place to the temple of the Graces-to promote the requital of services; for this is characteristic of
grace-we should serve in return one who has shown grace to us, and should another time take the initiative in
showing it.

Now proportionate return is secured by cross-conjunction. Let A be a builder, B a shoemaker, C a house, D a
shoe. The builder, then, must get from the shoemaker the latter's work, and must himself give him in return
his own. If, then, first there is proportionate equality of goods, and then reciprocal action takes place, the
result we mention will be effected. If not, the bargain is not equal, and does not hold; for there is nothing to
prevent the work of the one being better than that of the other; they must therefore be equated. (And this is
true of the other arts also; for they would have been destroyed if what the patient suffered had not been just
what the agent did, and of the same amount and kind.) For it is not two doctors that associate for exchange,
but a doctor and a farmer, or in general people who are different and unequal; but these must be equated. This
is why all things that are exchanged must be somehow comparable. It is for this end that money has been
introduced, and it becomes in a sense an intermediate; for it measures all things, and therefore the excess and
the defect-how many shoes are equal to a house or to a given amount of food. The number of shoes
exchanged for a house (or for a given amount of food) must therefore correspond to the ratio of builder to
shoemaker. For if this be not so, there will be no exchange and no intercourse. And this proportion will not be
effected unless the goods are somehow equal. All goods must therefore be measured by some one thing, as
we said before. Now this unit is in truth demand, which holds all things together (for if men did not need one
another's goods at all, or did not need them equally, there would be either no exchange or not the same
exchange); but money has become by convention a sort of representative of demand; and this is why it has
the name 'money' (nomisma)-because it exists not by nature but by law (nomos) and it is in our power to
change it and make it useless. There will, then, be reciprocity when the terms have been equated so that as
farmer is to shoemaker, the amount of the shoemaker's work is to that of the farmer's work for which it
exchanges. But we must not bring them into a figure of proportion when they have already exchanged
(otherwise one extreme will have both excesses), but when they still have their own goods. Thus they are
equals and associates just because this equality can be effected in their case. Let A be a farmer, C food, B a
shoemaker, D his product equated to C. If it had not been possible for reciprocity to be thus effected, there
would have been no association of the parties. That demand holds things together as a single unit is shown by
the fact that when men do not need one another, i.e. when neither needs the other or one does not need the

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other, they do not exchange, as we do when some one wants what one has oneself, e.g. when people permit
the exportation of corn in exchange for wine. This equation therefore must be established. And for the future
exchange-that if we do not need a thing now we shall have it if ever we do need it-money is as it were our
surety; for it must be possible for us to get what we want by bringing the money. Now the same thing
happens to money itself as to goods-it is not always worth the same; yet it tends to be steadier. This is why
all goods must have a price set on them; for then there will always be exchange, and if so, association of man
with man. Money, then, acting as a measure, makes goods commensurate and equates them; for neither
would there have been association if there were not exchange, nor exchange if there were not equality, nor
equality if there were not commensur ability. Now in truth it is impossible that things differing so much
should become commensurate, but with reference to demand they may become so sufficiently. There must,
then, be a unit, and that fixed by agreement (for which reason it is called money); for it is this that makes all
things commensurate, since all things are measured by money. Let A be a house, B ten minae, C a bed. A is
half of B, if the house is worth five minae or equal to them; the bed, C, is a tenth of B; it is plain, then, how
many beds are equal to a house, viz. five. That exchange took place thus before there was money is plain; for
it makes no difference whether it is five beds that exchange for a house, or the money value of five beds.

We have now defined the unjust and the just. These having been marked off from each other, it is plain that
just action is intermediate between acting unjustly and being unjustly treated; for the one is to have too much
and the other to have too little. Justice is a kind of mean, but not in the same way as the other virtues, but
because it relates to an intermediate amount, while injustice relates to the extremes. And justice is that in
virtue of which the just man is said to be a doer, by choice, of that which is just, and one who will distribute
either between himself and another or between two others not so as to give more of what is desirable to
himself and less to his neighbour (and conversely with what is harmful), but so as to give what is equal in
accordance with proportion; and similarly in distributing between two other persons. Injustice on the other
hand is similarly related to the unjust, which is excess and defect, contrary to proportion, of the useful or
hurtful. For which reason injustice is excess and defect, viz. because it is productive of excess and defect-in
one's own case excess of what is in its own nature useful and defect of what is hurtful, while in the case of
others it is as a whole like what it is in one's own case, but proportion may be violated in either direction. In
the unjust act to have too little is to be unjustly treated; to have too much is to act unjustly.

Let this be taken as our account of the nature of justice and injustice, and similarly of the just and the unjust
in general.

Since acting unjustly does not necessarily imply being unjust, we must ask what sort of unjust acts imply that
the doer is unjust with respect to each type of injustice, e.g. a thief, an adulterer, or a brigand. Surely the
answer does not turn on the difference between these types. For a man might even lie with a woman knowing
who she was, but the origin of his might be not deliberate choice but passion. He acts unjustly, then, but is
not unjust; e.g. a man is not a thief, yet he stole, nor an adulterer, yet he committed adultery; and similarly in
all other cases.

Now we have previously stated how the reciprocal is related to the just; but we must not forget that what we
are looking for is not only what is just without qualification but also political justice. This is found among
men who share their life with a view to selfsufficiency, men who are free and either proportionately or
arithmetically equal, so that between those who do not fulfil this condition there is no political justice but
justice in a special sense and by analogy. For justice exists only between men whose mutual relations are
governed by law; and law exists for men between whom there is injustice; for legal justice is the
discrimination of the just and the unjust. And between men between whom there is injustice there is also
unjust action (though there is not injustice between all between whom there is unjust action), and this is
assigning too much to oneself of things good in themselves and too little of things evil in themselves. This is
why we do not allow a man to rule, but rational principle, because a man behaves thus in his own interests
and becomes a tyrant. The magistrate on the other hand is the guardian of justice, and, if of justice, then of

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equality also. And since he is assumed to have no more than his share, if he is just (for he does not assign to
himself more of what is good in itself, unless such a share is proportional to his merits-so that it is for others
that he labours, and it is for this reason that men, as we stated previously, say that justice is 'another's good'),
therefore a reward must be given him, and this is honour and privilege; but those for whom such things are
not enough become tyrants.

The justice of a master and that of a father are not the same as the justice of citizens, though they are like it;
for there can be no injustice in the unqualified sense towards thing that are one's own, but a man's chattel, and
his child until it reaches a certain age and sets up for itself, are as it were part of himself, and no one chooses
to hurt himself (for which reason there can be no injustice towards oneself). Therefore the justice or injustice
of citizens is not manifested in these relations; for it was as we saw according to law, and between people
naturally subject to law, and these as we saw' are people who have an equal share in ruling and being ruled.
Hence justice can more truly be manifested towards a wife than towards children and chattels, for the former
is household justice; but even this is different from political justice.

Of political justice part is natural, part legal, natural, that which everywhere has the same force and does not
exist by people's thinking this or that; legal, that which is originally indifferent, but when it has been laid
down is not indifferent, e.g. that a prisoner's ransom shall be a mina, or that a goat and not two sheep shall be
sacrificed, and again all the laws that are passed for particular cases, e.g. that sacrifice shall be made in
honour of Brasidas, and the provisions of decrees. Now some think that all justice is of this sort, because that
which is by nature is unchangeable and has everywhere the same force (as fire burns both here and in Persia),
while they see change in the things recognized as just. This, however, is not true in this unqualified way, but
is true in a sense; or rather, with the gods it is perhaps not true at all, while with us there is something that is
just even by nature, yet all of it is changeable; but still some is by nature, some not by nature. It is evident
which sort of thing, among things capable of being otherwise, is by nature, and which is not but is legal and
conventional, assuming that both are equally changeable. And in all other things the same distinction will
apply; by nature the right hand is stronger, yet it is possible that all men should come to be ambidextrous. The
things which are just by virtue of convention and expediency are like measures; for wine and corn measures
are not everywhere equal, but larger in wholesale and smaller in retail markets. Similarly, the things which
are just not by nature but by human enactment are not everywhere the same, since constitutions also are not
the same, though there is but one which is everywhere by nature the best. Of things just and lawful each is
related as the universal to its particulars; for the things that are done are many, but of them each is one, since
it is universal.

There is a difference between the act of injustice and what is unjust, and between the act of justice and what
is just; for a thing is unjust by nature or by enactment; and this very thing, when it has been done, is an act of
injustice, but before it is done is not yet that but is unjust. So, too, with an act of justice (though the general
term is rather 'just action', and 'act of justice' is applied to the correction of the act of injustice).

Each of these must later be examined separately with regard to the nature and number of its species and the
nature of the things with which it is concerned.

Acts just and unjust being as we have described them, a man acts unjustly or justly whenever he does such
acts voluntarily; when involuntarily, he acts neither unjustly nor justly except in an incidental way; for he
does things which happen to be just or unjust. Whether an act is or is not one of injustice (or of justice) is
determined by its voluntariness or involuntariness; for when it is voluntary it is blamed, and at the same time
is then an act of injustice; so that there will be things that are unjust but not yet acts of injustice, if
voluntariness be not present as well. By the voluntary I mean, as has been said before, any of the things in a
man's own power which he does with knowledge, i.e. not in ignorance either of the person acted on or of the
instrument used or of the end that will be attained (e.g. whom he is striking, with what, and to what end),
each such act being done not incidentally nor under compulsion (e.g. if A takes B's hand and therewith strikes

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C, B does not act voluntarily; for the act was not in his own power). The person struck may be the striker's
father, and the striker may know that it is a man or one of the persons present, but not know that it is his
father; a similar distinction may be made in the case of the end, and with regard to the whole action.
Therefore that which is done in ignorance, or though not done in ignorance is not in the agent's power, or is
done under compulsion, is involuntary (for many natural processes, even, we knowingly both perform and
experience, none of which is either voluntary or involuntary; e.g. growing old or dying). But in the case of
unjust and just acts alike the injustice or justice may be only incidental; for a man might return a deposit
unwillingly and from fear, and then he must not be said either to do what is just or to act justly, except in an
incidental way. Similarly the man who under compulsion and unwillingly fails to return the deposit must be
said to act unjustly, and to do what is unjust, only incidentally. Of voluntary acts we do some by choice,
others not by choice; by choice those which we do after deliberation, not by choice those which we do
without previous deliberation. Thus there are three kinds of injury in transactions between man and man;
those done in ignorance are mistakes when the person acted on, the act, the instrument, or the end that will be
attained is other than the agent supposed; the agent thought either that he was not hiting any one or that he
was not hitting with this missile or not hitting this person or to this end, but a result followed other than that
which he thought likely (e.g. he threw not with intent to wound but only to prick), or the person hit or the
missile was other than he supposed. Now when (1) the injury takes place contrary to reasonable expectation,
it is a misadventure. When (2) it is not contrary to reasonable expectation, but does not imply vice, it is a
mistake (for a man makes a mistake when the fault originates in him, but is the victim of accident when the
origin lies outside him). When (3) he acts with knowledge but not after deliberation, it is an act of
injustice-e.g. the acts due to anger or to other passions necessary or natural to man; for when men do such
harmful and mistaken acts they act unjustly, and the acts are acts of injustice, but this does not imply that the
doers are unjust or wicked; for the injury is not due to vice. But when (4) a man acts from choice, he is an
unjust man and a vicious man.

Hence acts proceeding from anger are rightly judged not to be done of malice aforethought; for it is not the
man who acts in anger but he who enraged him that starts the mischief. Again, the matter in dispute is not
whether the thing happened or not, but its justice; for it is apparent injustice that occasions rage. For they do
not dispute about the occurrence of the act-as in commercial transactions where one of the two parties must
be vicious-unless they do so owing to forgetfulness; but, agreeing about the fact, they dispute on which side
justice lies (whereas a man who has deliberately injured another cannot help knowing that he has done so), so
that the one thinks he is being treated unjustly and the other disagrees.

But if a man harms another by choice, he acts unjustly; and these are the acts of injustice which imply that the
doer is an unjust man, provided that the act violates proportion or equality. Similarly, a man is just when he
acts justly by choice; but he acts justly if he merely acts voluntarily.

Of involuntary acts some are excusable, others not. For the mistakes which men make not only in ignorance
but also from ignorance are excusable, while those which men do not from ignorance but (though they do
them in ignorance) owing to a passion which is neither natural nor such as man is liable to, are not excusable.

Assuming that we have sufficiently defined the suffering and doing of injustice, it may be asked (1) whether
the truth in expressed in Euripides' paradoxical words:

I slew my mother, that's my tale in brief.
Were you both willing, or unwilling both?

Is it truly possible to be willingly treated unjustly, or is all suffering of injustice the contrary involuntary, as
all unjust action is voluntary? And is all suffering of injustice of the latter kind or else all of the former, or is
it sometimes voluntary, sometimes involuntary? So, too, with the case of being justly treated; all just action is
voluntary, so that it is reasonable that there should be a similar opposition in either case-that both being

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unjustly and being justly treated should be either alike voluntary or alike involuntary. But it would be thought
paradoxical even in the case of being justly treated, if it were always voluntary; for some are unwillingly
treated justly. (2) One might raise this question also, whether every one who has suffered what is unjust is
being unjustly treated, or on the other hand it is with suffering as with acting. In action and in passivity alike
it is possible to partake of justice incidentally, and similarly (it is plain) of injustice; for to do what is unjust is
not the same as to act unjustly, nor to suffer what is unjust as to be treated unjustly, and similarly in the case
of acting justly and being justly treated; for it is impossible to be unjustly treated if the other does not act
unjustly, or justly treated unless he acts justly. Now if to act unjustly is simply to harm some one voluntarily,
and 'voluntarily' means 'knowing the person acted on, the instrument, and the manner of one's acting', and the
incontinent man voluntarily harms himself, not only will he voluntarily be unjustly treated but it will be
possible to treat oneself unjustly. (This also is one of the questions in doubt, whether a man can treat himself
unjustly.) Again, a man may voluntarily, owing to incontinence, be harmed by another who acts voluntarily,
so that it would be possible to be voluntarily treated unjustly. Or is our definition incorrect; must we to
'harming another, with knowledge both of the person acted on, of the instrument, and of the manner' add
'contrary to the wish of the person acted on'? Then a man may be voluntarily harmed and voluntarily suffer
what is unjust, but no one is voluntarily treated unjustly; for no one wishes to be unjustly treated, not even the
incontinent man. He acts contrary to his wish; for no one wishes for what he does not think to be good, but
the incontinent man does do things that he does not think he ought to do. Again, one who gives what is his
own, as Homer says Glaucus gave Diomede

Armour of gold for brazen, the price of a hundred beeves for nine, is not unjustly treated; for though to give is
in his power, to be unjustly treated is not, but there must be some one to treat him unjustly. It is plain, then,
that being unjustly treated is not voluntary.

Of the questions we intended to discuss two still remain for discussion; (3) whether it is the man who has
assigned to another more than his share that acts unjustly, or he who has the excessive share, and (4) whether
it is possible to treat oneself unjustly. The questions are connected; for if the former alternative is possible
and the distributor acts unjustly and not the man who has the excessive share, then if a man assigns more to
another than to himself, knowingly and voluntarily, he treats himself unjustly; which is what modest people
seem to do, since the virtuous man tends to take less than his share. Or does this statement too need
qualification? For (a) he perhaps gets more than his share of some other good, e.g. of honour or of intrinsic
nobility, (b) The question is solved by applying the distinction we applied to unjust action; for he suffers
nothing contrary to his own wish, so that he is not unjustly treated as far as this goes, but at most only suffers
harm.

It is plain too that the distributor acts unjustly, but not always the man who has the excessive share; for it is
not he to whom what is unjust appertains that acts unjustly, but he to whom it appertains to do the unjust act
voluntarily, i.e. the person in whom lies the origin of the action, and this lies in the distributor, not in the
receiver. Again, since the word 'do' is ambiguous, and there is a sense in which lifeless things, or a hand, or a
servant who obeys an order, may be said to slay, he who gets an excessive share does not act unjustly, though
he 'does' what is unjust.

Again, if the distributor gave his judgement in ignorance, he does not act unjustly in respect of legal justice,
and his judgement is not unjust in this sense, but in a sense it is unjust (for legal justice and primordial justice
are different); but if with knowledge he judged unjustly, he is himself aiming at an excessive share either of
gratitude or of revenge. As much, then, as if he were to share in the plunder, the man who has judged unjustly
for these reasons has got too much; the fact that what he gets is different from what he distributes makes no
difference, for even if he awards land with a view to sharing in the plunder he gets not land but money.

Men think that acting unjustly is in their power, and therefore that being just is easy. But it is not; to lie with
one's neighbour's wife, to wound another, to deliver a bribe, is easy and in our power, but to do these things

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as a result of a certain state of character is neither easy nor in our power. Similarly to know what is just and
what is unjust requires, men think, no great wisdom, because it is not hard to understand the matters dealt
with by the laws (though these are not the things that are just, except incidentally); but how actions must be
done and distributions effected in order to be just, to know this is a greater achievement than knowing what is
good for the health; though even there, while it is easy to know that honey, wine, hellebore, cautery, and the
use of the knife are so, to know how, to whom, and when these should be applied with a view to producing
health, is no less an achievement than that of being a physician. Again, for this very reason men think that
acting unjustly is characteristic of the just man no less than of the unjust, because he would be not less but
even more capable of doing each of these unjust acts; for he could lie with a woman or wound a neighbour;
and the brave man could throw away his shield and turn to flight in this direction or in that. But to play the
coward or to act unjustly consists not in doing these things, except incidentally, but in doing them as the
result of a certain state of character, just as to practise medicine and healing consists not in applying or not
applying the knife, in using or not using medicines, but in doing so in a certain way.

Just acts occur between people who participate in things good in themselves and can have too much or too
little of them; for some beings (e.g. presumably the gods) cannot have too much of them, and to others, those
who are incurably bad, not even the smallest share in them is beneficial but all such goods are harmful, while
to others they are beneficial up to a point; therefore justice is essentially something human.

Our next subject is equity and the equitable (to epiekes), and their respective relations to justice and the just.
For on examination they appear to be neither absolutely the same nor generically different; and while we
sometime praise what is equitable and the equitable man (so that we apply the name by way of praise even to
instances of the other virtues, instead of 'good' meaning by epieikestebon that a thing is better), at other times,
when we reason it out, it seems strange if the equitable, being something different from the just, is yet
praiseworthy; for either the just or the equitable is not good, if they are different; or, if both are good, they are
the same.

These, then, are pretty much the considerations that give rise to the problem about the equitable; they are all
in a sense correct and not opposed to one another; for the equitable, though it is better than one kind of
justice, yet is just, and it is not as being a different class of thing that it is better than the just. The same thing,
then, is just and equitable, and while both are good the equitable is superior. What creates the problem is that
the equitable is just, but not the legally just but a correction of legal justice. The reason is that all law is
universal but about some things it is not possible to make a universal statement which shall be correct. In
those cases, then, in which it is necessary to speak universally, but not possible to do so correctly, the law
takes the usual case, though it is not ignorant of the possibility of error. And it is none the less correct; for the
error is in the law nor in the legislator but in the nature of the thing, since the matter of practical affairs is of
this kind from the start. When the law speaks universally, then, and a case arises on it which is not covered by
the universal statement, then it is right, where the legislator fails us and has erred by oversimplicity, to correct
the omission-to say what the legislator himself would have said had he been present, and would have put into
his law if he had known. Hence the equitable is just, and better than one kind of justice-not better than
absolute justice but better than the error that arises from the absoluteness of the statement. And this is the
nature of the equitable, a correction of law where it is defective owing to its universality. In fact this is the
reason why all things are not determined by law, that about some things it is impossible to lay down a law, so
that a decree is needed. For when the thing is indefinite the rule also is indefinite, like the leaden rule used in
making the Lesbian moulding; the rule adapts itself to the shape of the stone and is not rigid, and so too the
decree is adapted to the facts.

It is plain, then, what the equitable is, and that it is just and is better than one kind of justice. It is evident also
from this who the equitable man is; the man who chooses and does such acts, and is no stickler for his rights
in a bad sense but tends to take less than his share though he has the law oft his side, is equitable, and this
state of character is equity, which is a sort of justice and not a different state of character.

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Whether a man can treat himself unjustly or not, is evident from what has been said. For (a) one class of just
acts are those acts in accordance with any virtue which are prescribed by the law; e.g. the law does not
expressly permit suicide, and what it does not expressly permit it forbids. Again, when a man in violation of
the law harms another (otherwise than in retaliation) voluntarily, he acts unjustly, and a voluntary agent is
one who knows both the person he is affecting by his action and the instrument he is using; and he who
through anger voluntarily stabs himself does this contrary to the right rule of life, and this the law does not
allow; therefore he is acting unjustly. But towards whom? Surely towards the state, not towards himself. For
he suffers voluntarily, but no one is voluntarily treated unjustly. This is also the reason why the state
punishes; a certain loss of civil rights attaches to the man who destroys himself, on the ground that he is
treating the state unjustly.

Further (b) in that sense of 'acting unjustly' in which the man who 'acts unjustly' is unjust only and not bad all
round, it is not possible to treat oneself unjustly (this is different from the former sense; the unjust man in one
sense of the term is wicked in a particularized way just as the coward is, not in the sense of being wicked all
round, so that his 'unjust act' does not manifest wickedness in general). For (i) that would imply the
possibility of the same thing's having been subtracted from and added to the same thing at the same time; but
this is impossible-the just and the unjust always involve more than one person. Further, (ii) unjust action is
voluntary and done by choice, and takes the initiative (for the man who because he has suffered does the
same in return is not thought to act unjustly); but if a man harms himself he suffers and does the same things
at the same time. Further, (hi) if a man could treat himself unjustly, he could be voluntarily treated unjustly.
Besides, (iv) no one acts unjustly without committing particular acts of injustice; but no one can commit
adultery with his own wife or housebreaking on his own house or theft on his own property,

In general, the question 'can a man treat himself unjustly?' is solved also by the distinction we applied to the
question 'can a man be voluntarily treated unjustly?'

(It is evident too that both are bad, being unjustly treated and acting unjustly; for the one means having less
and the other having more than the intermediate amount, which plays the part here that the healthy does in the
medical art, and that good condition does in the art of bodily training. But still acting unjustly is the worse,
for it involves vice and is blameworthy-involves vice which is either of the complete and unqualified kind or
almost so (we must admit the latter alternative, because not all voluntary unjust action implies injustice as a
state of character), while being unjustly treated does not involve vice and injustice in oneself. In itself, then,
being unjustly treated is less bad, but there is nothing to prevent its being incidentally a greater evil. But
theory cares nothing for this; it calls pleurisy a more serious mischief than a stumble; yet the latter may
become incidentally the more serious, if the fall due to it leads to your being taken prisoner or put to death the
enemy.)

Metaphorically and in virtue of a certain resemblance there is a justice, not indeed between a man and
himself, but between certain parts of him; yet not every kind of justice but that of master and servant or that
of husband and wife. For these are the ratios in which the part of the soul that has a rational principle stands
to the irrational part; and it is with a view to these parts that people also think a man can be unjust to himself,
viz. because these parts are liable to suffer something contrary to their respective desires; there is therefore
thought to be a mutual justice between them as between ruler and ruled.

Let this be taken as our account of justice and the other, i.e. the other moral, virtues.

BOOK VI

SINCE we have previously said that one ought to choose that which is intermediate, not the excess nor the
defect, and that the intermediate is determined by the dictates of the right rule, let us discuss the nature of
these dictates. In all the states of character we have mentioned, as in all other matters, there is a mark to

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which the man who has the rule looks, and heightens or relaxes his activity accordingly, and there is a
standard which determines the mean states which we say are intermediate between excess and defect, being
in accordance with the right rule. But such a statement, though true, is by no means clear; for not only here
but in all other pursuits which are objects of knowledge it is indeed true to say that we must not exert
ourselves nor relax our efforts too much nor too little, but to an intermediate extent and as the right rule
dictates; but if a man had only this knowledge he would be none the wiser e.g. we should not know what sort
of medicines to apply to our body if some one were to say 'all those which the medical art prescribes, and
which agree with the practice of one who possesses the art'. Hence it is necessary with regard to the states of
the soul also not only that this true statement should be made, but also that it should be determined what is
the right rule and what is the standard that fixes it.

We divided the virtues of the soul and a said that some are virtues of character and others of intellect. Now
we have discussed in detail the moral virtues; with regard to the others let us express our view as follows,
beginning with some remarks about the soul. We said before that there are two parts of the soul-that which
grasps a rule or rational principle, and the irrational; let us now draw a similar distinction within the part
which grasps a rational principle. And let it be assumed that there are two parts which grasp a rational
principle-one by which we contemplate the kind of things whose originative causes are invariable, and one
by which we contemplate variable things; for where objects differ in kind the part of the soul answering to
each of the two is different in kind, since it is in virtue of a certain likeness and kinship with their objects that
they have the knowledge they have. Let one of these parts be called the scientific and the other the
calculative; for to deliberate and to calculate are the same thing, but no one deliberates about the invariable.
Therefore the calculative is one part of the faculty which grasps a rational principle. We must, then, learn
what is the best state of each of these two parts; for this is the virtue of each.

The virtue of a thing is relative to its proper work. Now there are three things in the soul which control action
and truth-sensation, reason, desire.

Of these sensation originates no action; this is plain from the fact that the lower animals have sensation but
no share in action.

What affirmation and negation are in thinking, pursuit and avoidance are in desire; so that since moral virtue
is a state of character concerned with choice, and choice is deliberate desire, therefore both the reasoning
must be true and the desire right, if the choice is to be good, and the latter must pursue just what the former
asserts. Now this kind of intellect and of truth is practical; of the intellect which is contemplative, not
practical nor productive, the good and the bad state are truth and falsity respectively (for this is the work of
everything intellectual); while of the part which is practical and intellectual the good state is truth in
agreement with right desire.

The origin of action-its efficient, not its final cause-is choice, and that of choice is desire and reasoning with
a view to an end. This is why choice cannot exist either without reason and intellect or without a moral state;
for good action and its opposite cannot exist without a combination of intellect and character. Intellect itself,
however, moves nothing, but only the intellect which aims at an end and is practical; for this rules the
productive intellect, as well, since every one who makes makes for an end, and that which is made is not an
end in the unqualified sense (but only an end in a particular relation, and the end of a particular
operation)-only that which is done is that; for good action is an end, and desire aims at this. Hence choice is
either desiderative reason or ratiocinative desire, and such an origin of action is a man. (It is to be noted that
nothing that is past is an object of choice, e.g. no one chooses to have sacked Troy; for no one deliberates
about the past, but about what is future and capable of being otherwise, while what is past is not capable of
not having taken place; hence Agathon is right in saying

For this alone is lacking even to God,
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To make undone things that have once been done.)

The work of both the intellectual parts, then, is truth. Therefore the states that are most strictly those in
respect of which each of these parts will reach truth are the virtues of the two parts.

Let us begin, then, from the beginning, and discuss these states once more. Let it be assumed that the states
by virtue of which the soul possesses truth by way of affirmation or denial are five in number, i.e. art,
scientific knowledge, practical wisdom, philosophic wisdom, intuitive reason; we do not include judgement
and opinion because in these we may be mistaken.

Now what scientific knowledge is, if we are to speak exactly and not follow mere similarities, is plain from
what follows. We all suppose that what we know is not even capable of being otherwise; of things capable of
being otherwise we do not know, when they have passed outside our observation, whether they exist or not.
Therefore the object of scientific knowledge is of necessity. Therefore it is eternal; for things that are of
necessity in the unqualified sense are all eternal; and things that are eternal are ungenerated and imperishable.
Again, every science is thought to be capable of being taught, and its object of being learned. And all
teaching starts from what is already known, as we maintain in the Analytics also; for it proceeds sometimes
through induction and sometimes by syllogism. Now induction is the starting-point which knowledge even
of the universal presupposes, while syllogism proceeds from universals. There are therefore starting-points
from which syllogism proceeds, which are not reached by syllogism; it is therefore by induction that they are
acquired. Scientific knowledge is, then, a state of capacity to demonstrate, and has the other limiting
characteristics which we specify in the Analytics, for it is when a man believes in a certain way and the
starting-points are known to him that he has scientific knowledge, since if they are not better known to him
than the conclusion, he will have his knowledge only incidentally.

Let this, then, be taken as our account of scientific knowledge.

In the variable are included both things made and things done; making and acting are different (for their
nature we treat even the discussions outside our school as reliable); so that the reasoned state of capacity to
act is different from the reasoned state of capacity to make. Hence too they are not included one in the other;
for neither is acting making nor is making acting. Now since architecture is an art and is essentially a
reasoned state of capacity to make, and there is neither any art that is not such a state nor any such state that
is not an art, art is identical with a state of capacity to make, involving a true course of reasoning. All art is
concerned with coming into being, i.e. with contriving and considering how something may come into being
which is capable of either being or not being, and whose origin is in the maker and not in the thing made; for
art is concerned neither with things that are, or come into being, by necessity, nor with things that do so in
accordance with nature (since these have their origin in themselves). Making and acting being different, art
must be a matter of making, not of acting. And in a sense chance and art are concerned with the same objects;
as Agathon says, 'art loves chance and chance loves art'. Art, then, as has been is a state concerned with
making, involving a true course of reasoning, and lack of art on the contrary is a state concerned with
making, involving a false course of reasoning; both are concerned with the variable.

Regarding practical wisdom we shall get at the truth by considering who are the persons we credit with it.
Now it is thought to be the mark of a man of practical wisdom to be able to deliberate well about what is
good and expedient for himself, not in some particular respect, e.g. about what sorts of thing conduce to
health or to strength, but about what sorts of thing conduce to the good life in general. This is shown by the
fact that we credit men with practical wisdom in some particular respect when they have calculated well with
a view to some good end which is one of those that are not the object of any art. It follows that in the general
sense also the man who is capable of deliberating has practical wisdom. Now no one deliberates about things
that are invariable, nor about things that it is impossible for him to do. Therefore, since scientific knowledge
involves demonstration, but there is no demonstration of things whose first principles are variable (for all

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such things might actually be otherwise), and since it is impossible to deliberate about things that are of
necessity, practical wisdom cannot be scientific knowledge nor art; not science because that which can be
done is capable of being otherwise, not art because action and making are different kinds of thing. The
remaining alternative, then, is that it is a true and reasoned state of capacity to act with regard to the things
that are good or bad for man. For while making has an end other than itself, action cannot; for good action
itself is its end. It is for this reason that we think Pericles and men like him have practical wisdom, viz.
because they can see what is good for themselves and what is good for men in general; we consider that those
can do this who are good at managing households or states. (This is why we call temperance (sophrosune) by
this name; we imply that it preserves one's practical wisdom (sozousa tan phronsin). Now what it preserves is
a judgement of the kind we have described. For it is not any and every judgement that pleasant and painful
objects destroy and pervert, e.g. the judgement that the triangle has or has not its angles equal to two right
angles, but only judgements about what is to be done. For the originating causes of the things that are done
consist in the end at which they are aimed; but the man who has been ruined by pleasure or pain forthwith
fails to see any such originating cause-to see that for the sake of this or because of this he ought to choose
and do whatever he chooses and does; for vice is destructive of the originating cause of action.) Practical
wisdom, then, must be a reasoned and true state of capacity to act with regard to human goods. But further,
while there is such a thing as excellence in art, there is no such thing as excellence in practical wisdom; and
in art he who errs willingly is preferable, but in practical wisdom, as in the virtues, he is the reverse. Plainly,
then, practical wisdom is a virtue and not an art. There being two parts of the soul that can follow a course of
reasoning, it must be the virtue of one of the two, i.e. of that part which forms opinions; for opinion is about
the variable and so is practical wisdom. But yet it is not only a reasoned state; this is shown by the fact that a
state of that sort may forgotten but practical wisdom cannot.

Scientific knowledge is judgement about things that are universal and necessary, and the conclusions of
demonstration, and all scientific knowledge, follow from first principles (for scientific knowledge involves
apprehension of a rational ground). This being so, the first principle from which what is scientifically known
follows cannot be an object of scientific knowledge, of art, or of practical wisdom; for that which can be
scientifically known can be demonstrated, and art and practical wisdom deal with things that are variable.
Nor are these first principles the objects of philosophic wisdom, for it is a mark of the philosopher to have
demonstration about some things. If, then, the states of mind by which we have truth and are never deceived
about things invariable or even variable are scientific knowlededge, practical wisdom, philosophic wisdom,
and intuitive reason, and it cannot be any of the three (i.e. practical wisdom, scientific knowledge, or
philosophic wisdom), the remaining alternative is that it is intuitive reason that grasps the first principles.

Wisdom (1) in the arts we ascribe to their most finished exponents, e.g. to Phidias as a sculptor and to
Polyclitus as a maker of portrait-statues, and here we mean nothing by wisdom except excellence in art; but
(2) we think that some people are wise in general, not in some particular field or in any other limited respect,
as Homer says in the Margites,

Him did the gods make neither a digger nor yet a ploughman
Nor wise in anything else.

Therefore wisdom must plainly be the most finished of the forms of knowledge. It follows that the wise man
must not only know what follows from the first principles, but must also possess truth about the first
principles. Therefore wisdom must be intuitive reason combined with scientific knowledge-scientific
knowledge of the highest objects which has received as it were its proper completion.

Of the highest objects, we say; for it would be strange to think that the art of politics, or practical wisdom, is
the best knowledge, since man is not the best thing in the world. Now if what is healthy or good is different
for men and for fishes, but what is white or straight is always the same, any one would say that what is wise
is the same but what is practically wise is different; for it is to that which observes well the various matters

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concerning itself that one ascribes practical wisdom, and it is to this that one will entrust such matters. This is
why we say that some even of the lower animals have practical wisdom, viz. those which are found to have a
power of foresight with regard to their own life. It is evident also that philosophic wisdom and the art of
politics cannot be the same; for if the state of mind concerned with a man's own interests is to be called
philosophic wisdom, there will be many philosophic wisdoms; there will not be one concerned with the good
of all animals (any more than there is one art of medicine for all existing things), but a different philosophic
wisdom about the good of each species.

But if the argument be that man is the best of the animals, this makes no difference; for there are other things
much more divine in their nature even than man, e.g., most conspicuously, the bodies of which the heavens
are framed. From what has been said it is plain, then, that philosophic wisdom is scientific knowledge,
combined with intuitive reason, of the things that are highest by nature. This is why we say Anaxagoras,
Thales, and men like them have philosophic but not practical wisdom, when we see them ignorant of what is
to their own advantage, and why we say that they know things that are remarkable, admirable, difficult, and
divine, but useless; viz. because it is not human goods that they seek.

Practical wisdom on the other hand is concerned with things human and things about which it is possible to
deliberate; for we say this is above all the work of the man of practical wisdom, to deliberate well, but no one
deliberates about things invariable, nor about things which have not an end, and that a good that can be
brought about by action. The man who is without qualification good at deliberating is the man who is capable
of aiming in accordance with calculation at the best for man of things attainable by action. Nor is practical
wisdom concerned with universals only-it must also recognize the particulars; for it is practical, and practice
is concerned with particulars. This is why some who do not know, and especially those who have experience,
are more practical than others who know; for if a man knew that light meats are digestible and wholesome,
but did not know which sorts of meat are light, he would not produce health, but the man who knows that
chicken is wholesome is more likely to produce health.

Now practical wisdom is concerned with action; therefore one should have both forms of it, or the latter in
preference to the former. But of practical as of philosophic wisdom there must be a controlling kind.

Political wisdom and practical wisdom are the same state of mind, but their essence is not the same. Of the
wisdom concerned with the city, the practical wisdom which plays a controlling part is legislative wisdom,
while that which is related to this as particulars to their universal is known by the general name 'political
wisdom'; this has to do with action and deliberation, for a decree is a thing to be carried out in the form of an
individual act. This is why the exponents of this art are alone said to 'take part in polities'; for these alone 'do
things' as manual labourers 'do things'.

Practical wisdom also is identified especially with that form of it which is concerned with a man
himself-with the individual; and this is known by the general name 'practical wisdom'; of the other kinds one
is called household management, another legislation, the third politics, and of the latter one part is called
deliberative and the other judicial. Now knowing what is good for oneself will be one kind of knowledge, but
it is very different from the other kinds; and the man who knows and concerns himself with his own interests
is thought to have practical wisdom, while politicians are thought to be busybodies; hence the word of
Euripides,

But how could I be wise, who might at ease,
Numbered among the army's multitude,
Have had an equal share?
For those who aim too high and do too much.

Those who think thus seek their own good, and consider that one ought to do so. From this opinion, then, has
come the view that such men have practical wisdom; yet perhaps one's own good cannot exist without

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household management, nor without a form of government. Further, how one should order one's own affairs
is not clear and needs inquiry.

What has been said is confirmed by the fact that while young men become geometricians and mathematicians
and wise in matters like these, it is thought that a young man of practical wisdom cannot be found. The cause
is that such wisdom is concerned not only with universals but with particulars, which become familiar from
experience, but a young man has no experience, for it is length of time that gives experience; indeed one
might ask this question too, why a boy may become a mathematician, but not a philosopher or a physicist. It
is because the objects of mathematics exist by abstraction, while the first principles of these other subjects
come from experience, and because young men have no conviction about the latter but merely use the proper
language, while the essence of mathematical objects is plain enough to them?

Further, error in deliberation may be either about the universal or about the particular; we may fall to know
either that all water that weighs heavy is bad, or that this particular water weighs heavy.

That practical wisdom is not scientific knowledge is evident; for it is, as has been said, concerned with the
ultimate particular fact, since the thing to be done is of this nature. It is opposed, then, to intuitive reason; for
intuitive reason is of the limiting premisses, for which no reason can be given, while practical wisdom is
concerned with the ultimate particular, which is the object not of scientific knowledge but of perception-not
the perception of qualities peculiar to one sense but a perception akin to that by which we perceive that the
particular figure before us is a triangle; for in that direction as well as in that of the major premiss there will
be a limit. But this is rather perception than practical wisdom, though it is another kind of perception than
that of the qualities peculiar to each sense.

There is a difference between inquiry and deliberation; for deliberation is inquiry into a particular kind of
thing. We must grasp the nature of excellence in deliberation as well whether it is a form of scientific
knowledge, or opinion, or skill in conjecture, or some other kind of thing. Scientific knowledge it is not; for
men do not inquire about the things they know about, but good deliberation is a kind of deliberation, and he
who deliberates inquires and calculates. Nor is it skill in conjecture; for this both involves no reasoning and is
something that is quick in its operation, while men deliberate a long time, and they say that one should carry
out quickly the conclusions of one's deliberation, but should deliberate slowly. Again, readiness of mind is
different from excellence in deliberation; it is a sort of skill in conjecture. Nor again is excellence in
deliberation opinion of any sort. But since the man who deliberates badly makes a mistake, while he who
deliberates well does so correctly, excellence in deliberation is clearly a kind of correctness, but neither of
knowledge nor of opinion; for there is no such thing as correctness of knowledge (since there is no such thing
as error of knowledge), and correctness of opinion is truth; and at the same time everything that is an object
of opinion is already determined. But again excellence in deliberation involves reasoning. The remaining
alternative, then, is that it is correctness of thinking; for this is not yet assertion, since, while even opinion is
not inquiry but has reached the stage of assertion, the man who is deliberating, whether he does so well or ill,
is searching for something and calculating.

But excellence in deliberation is a certain correctness of deliberation; hence we must first inquire what
deliberation is and what it is about. And, there being more than one kind of correctness, plainly excellence in
deliberation is not any and every kind; for (1) the incontinent man and the bad man, if he is clever, will reach
as a result of his calculation what he sets before himself, so that he will have deliberated correctly, but he will
have got for himself a great evil. Now to have deliberated well is thought to be a good thing; for it is this kind
of correctness of deliberation that is excellence in deliberation, viz. that which tends to attain what is good.
But (2) it is possible to attain even good by a false syllogism, and to attain what one ought to do but not by
the right means, the middle term being false; so that this too is not yet excellence in deliberation this state in
virtue of which one attains what one ought but not by the right means. Again (3) it is possible to attain it by
long deliberation while another man attains it quickly. Therefore in the former case we have not yet got

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excellence in deliberation, which is Tightness with regard to the expedient-rightness in respect both of the
end, the manner, and the time. (4) Further it is possible to have deliberated well either in the unqualified
sense or with reference to a particular end. Excellence in deliberation in the unqualified sense, then, is that
which succeeds with reference to what is the end in the unqualified sense, and excellence in deliberation in a
particular sense is that which succeeds relatively to a particular end. If, then, it is characteristic of men of
practical wisdom to have deliberated well, excellence in deliberation will be correctness with regard to what
conduces to the end of which practical wisdom is the true apprehension.

Understanding, also, and goodness of understanding, in virtue of which men are said to be men of
understanding or of good understanding, are neither entirely the same as opinion or scientific knowledge (for
at that rate all men would have been men of understanding), nor are they one of the particular sciences, such
as medicine, the science of things connected with health, or geometry, the science of spatial magnitudes. For
understanding is neither about things that are always and are unchangeable, nor about any and every one of
the things that come into being, but about things which may become subjects of questioning and deliberation.
Hence it is about the same objects as practical wisdom; but understanding and practical wisdom are not the
same. For practical wisdom issues commands, since its end is what ought to be done or not to be done; but
understanding only judges. (Understanding is identical with goodness of understanding, men of
understanding with men of good understanding.) Now understanding is neither the having nor the acquiring
of practical wisdom; but as learning is called understanding when it means the exercise of the faculty of
knowledge, so 'understanding' is applicable to the exercise of the faculty of opinion for the purpose of judging
of what some one else says about matters with which practical wisdom is concerned-and of judging soundly;
for 'well' and 'soundly' are the same thing. And from this has come the use of the name 'understanding' in
virtue of which men are said to be 'of good understanding', viz. from the application of the word to the
grasping of scientific truth; for we often call such grasping understanding.

What is called judgement, in virtue of which men are said to 'be sympathetic judges' and to 'have judgement',
is the right discrimination of the equitable. This is shown by the fact that we say the equitable man is above
all others a man of sympathetic judgement, and identify equity with sympathetic judgement about certain
facts. And sympathetic judgement is judgement which discriminates what is equitable and does so correctly;
and correct judgement is that which judges what is true.

Now all the states we have considered converge, as might be expected, to the same point; for when we speak
of judgement and understanding and practical wisdom and intuitive reason we credit the same people with
possessing judgement and having reached years of reason and with having practical wisdom and
understanding. For all these faculties deal with ultimates, i.e. with particulars; and being a man of
understanding and of good or sympathetic judgement consists in being able judge about the things with which
practical wisdom is concerned; for the equities are common to all good men in relation to other men. Now all
things which have to be done are included among particulars or ultimates; for not only must the man of
practical wisdom know particular facts, but understanding and judgement are also concerned with things to
be done, and these are ultimates. And intuitive reason is concerned with the ultimates in both directions; for
both the first terms and the last are objects of intuitive reason and not of argument, and the intuitive reason
which is presupposed by demonstrations grasps the unchangeable and first terms, while the intuitive reason
involved in practical reasonings grasps the last and variable fact, i.e. the minor premiss. For these variable
facts are the starting-points for the apprehension of the end, since the universals are reached from the
particulars; of these therefore we must have perception, and this perception is intuitive reason.

This is why these states are thought to be natural endowments-why, while no one is thought to be a
philosopher by nature, people are thought to have by nature judgement, understanding, and intuitive reason.
This is shown by the fact that we think our powers correspond to our time of life, and that a particular age
brings with it intuitive reason and judgement; this implies that nature is the cause. (Hence intuitive reason is
both beginning and end; for demonstrations are from these and about these.) Therefore we ought to attend to

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the undemonstrated sayings and opinions of experienced and older people or of people of practical wisdom
not less than to demonstrations; for because experience has given them an eye they see aright.

We have stated, then, what practical and philosophic wisdom are, and with what each of them is concerned,
and we have said that each is the virtue of a different part of the soul.

Difficulties might be raised as to the utility of these qualities of mind. For (1) philosophic wisdom will
contemplate none of the things that will make a man happy (for it is not concerned with any coming into
being), and though practical wisdom has this merit, for what purpose do we need it? Practical wisdom is the
quality of mind concerned with things just and noble and good for man, but these are the things which it is
the mark of a good man to do, and we are none the more able to act for knowing them if the virtues are states
of character, just as we are none the better able to act for knowing the things that are healthy and sound, in
the sense not of producing but of issuing from the state of health; for we are none the more able to act for
having the art of medicine or of gymnastics. But (2) if we are to say that a man should have practical wisdom
not for the sake of knowing moral truths but for the sake of becoming good, practical wisdom will be of no
use to those who are good; again it is of no use to those who have not virtue; for it will make no difference
whether they have practical wisdom themselves or obey others who have it, and it would be enough for us to
do what we do in the case of health; though we wish to become healthy, yet we do not learn the art of
medicine. (3) Besides this, it would be thought strange if practical wisdom, being inferior to philosophic
wisdom, is to be put in authority over it, as seems to be implied by the fact that the art which produces
anything rules and issues commands about that thing.

These, then, are the questions we must discuss; so far we have only stated the difficulties.

(1) Now first let us say that in themselves these states must be worthy of choice because they are the virtues
of the two parts of the soul respectively, even if neither of them produce anything.

(2) Secondly, they do produce something, not as the art of medicine produces health, however, but as health
produces health; so does philosophic wisdom produce happiness; for, being a part of virtue entire, by being
possessed and by actualizing itself it makes a man happy.

(3) Again, the work of man is achieved only in accordance with practical wisdom as well as with moral
virtue; for virtue makes us aim at the right mark, and practical wisdom makes us take the right means. (Of the
fourth part of the soul-the nutritive-there is no such virtue; for there is nothing which it is in its power to do
or not to do.)

(4) With regard to our being none the more able to do because of our practical wisdom what is noble and just,
let us begin a little further back, starting with the following principle. As we say that some people who do just
acts are not necessarily just, i.e. those who do the acts ordained by the laws either unwillingly or owing to
ignorance or for some other reason and not for the sake of the acts themselves (though, to be sure, they do
what they should and all the things that the good man ought), so is it, it seems, that in order to be good one
must be in a certain state when one does the several acts, i.e. one must do them as a result of choice and for
the sake of the acts themselves. Now virtue makes the choice right, but the question of the things which
should naturally be done to carry out our choice belongs not to virtue but to another faculty. We must devote
our attention to these matters and give a clearer statement about them. There is a faculty which is called
cleverness; and this is such as to be able to do the things that tend towards the mark we have set before
ourselves, and to hit it. Now if the mark be noble, the cleverness is laudable, but if the mark be bad, the
cleverness is mere smartness; hence we call even men of practical wisdom clever or smart. Practical wisdom
is not the faculty, but it does not exist without this faculty. And this eye of the soul acquires its formed state
not without the aid of virtue, as has been said and is plain; for the syllogisms which deal with acts to be done
are things which involve a starting-point, viz. 'since the end, i.e. what is best, is of such and such a nature',

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whatever it may be (let it for the sake of argument be what we please); and this is not evident except to the
good man; for wickedness perverts us and causes us to be deceived about the starting-points of action.
Therefore it is evident that it is impossible to be practically wise without being good.

We must therefore consider virtue also once more; for virtue too is similarly related; as practical wisdom is to
cleverness-not the same, but like it-so is natural virtue to virtue in the strict sense. For all men think that
each type of character belongs to its possessors in some sense by nature; for from the very moment of birth
we are just or fitted for selfcontrol or brave or have the other moral qualities; but yet we seek something else
as that which is good in the strict sense-we seek for the presence of such qualities in another way. For both
children and brutes have the natural dispositions to these qualities, but without reason these are evidently
hurtful. Only we seem to see this much, that, while one may be led astray by them, as a strong body which
moves without sight may stumble badly because of its lack of sight, still, if a man once acquires reason, that
makes a difference in action; and his state, while still like what it was, will then be virtue in the strict sense.
Therefore, as in the part of us which forms opinions there are two types, cleverness and practical wisdom, so
too in the moral part there are two types, natural virtue and virtue in the strict sense, and of these the latter
involves practical wisdom. This is why some say that all the virtues are forms of practical wisdom, and why
Socrates in one respect was on the right track while in another he went astray; in thinking that all the virtues
were forms of practical wisdom he was wrong, but in saying they implied practical wisdom he was right. This
is confirmed by the fact that even now all men, when they define virtue, after naming the state of character
and its objects add 'that (state) which is in accordance with the right rule'; now the right rule is that which is
in accordance with practical wisdom. All men, then, seem somehow to divine that this kind of state is virtue,
viz. that which is in accordance with practical wisdom. But we must go a little further. For it is not merely the
state in accordance with the right rule, but the state that implies the presence of the right rule, that is virtue;
and practical wisdom is a right rule about such matters. Socrates, then, thought the virtues were rules or
rational principles (for he thought they were, all of them, forms of scientific knowledge), while we think they
involve a rational principle.

It is clear, then, from what has been said, that it is not possible to be good in the strict sense without practical
wisdom, nor practically wise without moral virtue. But in this way we may also refute the dialectical
argument whereby it might be contended that the virtues exist in separation from each other; the same man, it
might be said, is not best equipped by nature for all the virtues, so that he will have already acquired one
when he has not yet acquired another. This is possible in respect of the natural virtues, but not in respect of
those in respect of which a man is called without qualification good; for with the presence of the one quality,
practical wisdom, will be given all the virtues. And it is plain that, even if it were of no practical value, we
should have needed it because it is the virtue of the part of us in question; plain too that the choice will not be
right without practical wisdom any more than without virtue; for the one deter, mines the end and the other
makes us do the things that lead to the end.

But again it is not supreme over philosophic wisdom, i.e. over the superior part of us, any more than the art of
medicine is over health; for it does not use it but provides for its coming into being; it issues orders, then, for
its sake, but not to it. Further, to maintain its supremacy would be like saying that the art of politics rules the
gods because it issues orders about all the affairs of the state.

BOOK VII

LET us now make a fresh beginning and point out that of moral states to be avoided there are three
kinds-vice, incontinence, brutishness. The contraries of two of these are evident,-one we call virtue, the
other continence; to brutishness it would be most fitting to oppose superhuman virtue, a heroic and divine
kind of virtue, as Homer has represented Priam saying of Hector that he was very good,

For he seemed not, he,
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The child of a mortal man, but as one that of God's seed came.

Therefore if, as they say, men become gods by excess of virtue, of this kind must evidently be the state
opposed to the brutish state; for as a brute has no vice or virtue, so neither has a god; his state is higher than
virtue, and that of a brute is a different kind of state from vice.

Now, since it is rarely that a godlike man is found-to use the epithet of the Spartans, who when they admire
any one highly call him a 'godlike man'-so too the brutish type is rarely found among men; it is found chiefly
among barbarians, but some brutish qualities are also produced by disease or deformity; and we also call by
this evil name those men who go beyond all ordinary standards by reason of vice. Of this kind of disposition,
however, we must later make some mention, while we have discussed vice before we must now discuss
incontinence and softness (or effeminacy), and continence and endurance; for we must treat each of the two
neither as identical with virtue or wickedness, nor as a different genus. We must, as in all other cases, set the
observed facts before us and, after first discussing the difficulties, go on to prove, if possible, the truth of all
the common opinions about these affections of the mind, or, failing this, of the greater number and the most
authoritative; for if we both refute the objections and leave the common opinions undisturbed, we shall have
proved the case sufficiently.

Now (1) both continence and endurance are thought to be included among things good and praiseworthy, and
both incontinence and soft, ness among things bad and blameworthy; and the same man is thought to be
continent and ready to abide by the result of his calculations, or incontinent and ready to abandon them. And
(2) the incontinent man, knowing that what he does is bad, does it as a result of passion, while the continent
man, knowing that his appetites are bad, refuses on account of his rational principle to follow them (3) The
temperate man all men call continent and disposed to endurance, while the continent man some maintain to
be always temperate but others do not; and some call the self-indulgent man incontinent and the incontinent
man selfindulgent indiscriminately, while others distinguish them. (4) The man of practical wisdom, they
sometimes say, cannot be incontinent, while sometimes they say that some who are practically wise and
clever are incontinent. Again (5) men are said to be incontinent even with respect to anger, honour, and
gain.-These, then, are the things that are said.

Now we may ask (1) how a man who judges rightly can behave incontinently. That he should behave so
when he has knowledge, some say is impossible; for it would be strange-so Socrates thought-if when
knowledge was in a man something else could master it and drag it about like a slave. For Socrates was
entirely opposed to the view in question, holding that there is no such thing as incontinence; no one, he said,
when he judges acts against what he judges best-people act so only by reason of ignorance. Now this view
plainly contradicts the observed facts, and we must inquire about what happens to such a man; if he acts by
reason of ignorance, what is the manner of his ignorance? For that the man who behaves incontinently does
not, before he gets into this state, think he ought to act so, is evident. But there are some who concede certain
of Socrates' contentions but not others; that nothing is stronger than knowledge they admit, but not that on
one acts contrary to what has seemed to him the better course, and therefore they say that the incontinent man
has not knowledge when he is mastered by his pleasures, but opinion. But if it is opinion and not knowledge,
if it is not a strong conviction that resists but a weak one, as in men who hesitate, we sympathize with their
failure to stand by such convictions against strong appetites; but we do not sympathize with wickedness, nor
with any of the other blameworthy states. Is it then practical wisdom whose resistance is mastered? That is
the strongest of all states. But this is absurd; the same man will be at once practically wise and incontinent,
but no one would say that it is the part of a practically wise man to do willingly the basest acts. Besides, it has
been shown before that the man of practical wisdom is one who will act (for he is a man concerned with the
individual facts) and who has the other virtues.

(2) Further, if continence involves having strong and bad appetites, the temperate man will not be continent
nor the continent man temperate; for a temperate man will have neither excessive nor bad appetites. But the

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continent man must; for if the appetites are good, the state of character that restrains us from following them
is bad, so that not all continence will be good; while if they are weak and not bad, there is nothing admirable
in resisting them, and if they are weak and bad, there is nothing great in resisting these either.

(3) Further, if continence makes a man ready to stand by any and every opinion, it is bad, i.e. if it makes him
stand even by a false opinion; and if incontinence makes a man apt to abandon any and every opinion, there
will be a good incontinence, of which Sophocles' Neoptolemus in the Philoctetes will be an instance; for he is
to be praised for not standing by what Odysseus persuaded him to do, because he is pained at telling a lie.

(4) Further, the sophistic argument presents a difficulty; the syllogism arising from men's wish to expose
paradoxical results arising from an opponent's view, in order that they may be admired when they succeed, is
one that puts us in a difficulty (for thought is bound fast when it will not rest because the conclusion does not
satisfy it, and cannot advance because it cannot refute the argument). There is an argument from which it
follows that folly coupled with incontinence is virtue; for a man does the opposite of what he judges, owing
to incontinence, but judges what is good to be evil and something that he should not do, and consequence he
will do what is good and not what is evil.

(5) Further, he who on conviction does and pursues and chooses what is pleasant would be thought to be
better than one who does so as a result not of calculation but of incontinence; for he is easier to cure since he
may be persuaded to change his mind. But to the incontinent man may be applied the proverb 'when water
chokes, what is one to wash it down with?' If he had been persuaded of the rightness of what he does, he
would have desisted when he was persuaded to change his mind; but now he acts in spite of his being
persuaded of something quite different.

(6) Further, if incontinence and continence are concerned with any and every kind of object, who is it that is
incontinent in the unqualified sense? No one has all the forms of incontinence, but we say some people are
incontinent without qualification.

Of some such kind are the difficulties that arise; some of these points must be refuted and the others left in
possession of the field; for the solution of the difficulty is the discovery of the truth. (1) We must consider
first, then, whether incontinent people act knowingly or not, and in what sense knowingly; then (2) with what
sorts of object the incontinent and the continent man may be said to be concerned (i.e. whether with any and
every pleasure and pain or with certain determinate kinds), and whether the continent man and the man of
endurance are the same or different; and similarly with regard to the other matters germane to this inquiry.
The starting-point of our investigation is (a) the question whether the continent man and the incontinent are
differentiated by their objects or by their attitude, i.e. whether the incontinent man is incontinent simply by
being concerned with such and such objects, or, instead, by his attitude, or, instead of that, by both these
things; (b) the second question is whether incontinence and continence are concerned with any and every
object or not. The man who is incontinent in the unqualified sense is neither concerned with any and every
object, but with precisely those with which the self-indulgent man is concerned, nor is he characterized by
being simply related to these (for then his state would be the same as self-indulgence), but by being related to
them in a certain way. For the one is led on in accordance with his own choice, thinking that he ought always
to pursue the present pleasure; while the other does not think so, but yet pursues it.

(1) As for the suggestion that it is true opinion and not knowledge against which we act incontinently, that
makes no difference to the argument; for some people when in a state of opinion do not hesitate, but think
they know exactly. If, then, the notion is that owing to their weak conviction those who have opinion are
more likely to act against their judgement than those who know, we answer that there need be no difference
between knowledge and opinion in this respect; for some men are no less convinced of what they think than
others of what they know; as is shown by the of Heraclitus. But (a), since we use the word 'know' in two
senses (for both the man who has knowledge but is not using it and he who is using it are said to know), it

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will make a difference whether, when a man does what he should not, he has the knowledge but is not
exercising it, or is exercising it; for the latter seems strange, but not the former.

(b) Further, since there are two kinds of premisses, there is nothing to prevent a man's having both premisses
and acting against his knowledge, provided that he is using only the universal premiss and not the particular;
for it is particular acts that have to be done. And there are also two kinds of universal term; one is predicable
of the agent, the other of the object; e.g. 'dry food is good for every man', and 'I am a man', or 'such and such
food is dry'; but whether 'this food is such and such', of this the incontinent man either has not or is not
exercising the knowledge. There will, then, be, firstly, an enormous difference between these manners of
knowing, so that to know in one way when we act incontinently would not seem anything strange, while to
know in the other way would be extraordinary.

And further (c) the possession of knowledge in another sense than those just named is something that happens
to men; for within the case of having knowledge but not using it we see a difference of state, admitting of the
possibility of having knowledge in a sense and yet not having it, as in the instance of a man asleep, mad, or
drunk. But now this is just the condition of men under the influence of passions; for outbursts of anger and
sexual appetites and some other such passions, it is evident, actually alter our bodily condition, and in some
men even produce fits of madness. It is plain, then, that incontinent people must be said to be in a similar
condition to men asleep, mad, or drunk. The fact that men use the language that flows from knowledge
proves nothing; for even men under the influence of these passions utter scientific proofs and verses of
Empedocles, and those who have just begun to learn a science can string together its phrases, but do not yet
know it; for it has to become part of themselves, and that takes time; so that we must suppose that the use of
language by men in an incontinent state means no more than its utterance by actors on the stage, (d) Again,
we may also view the cause as follows with reference to the facts of human nature. The one opinion is
universal, the other is concerned with the particular facts, and here we come to something within the sphere
of perception; when a single opinion results from the two, the soul must in one type of case affirm the
conclusion, while in the case of opinions concerned with production it must immediately act (e.g. if
'everything sweet ought to be tasted', and 'this is sweet', in the sense of being one of the particular sweet
things, the man who can act and is not prevented must at the same time actually act accordingly). When, then,
the universal opinion is present in us forbidding us to taste, and there is also the opinion that 'everything
sweet is pleasant', and that 'this is sweet' (now this is the opinion that is active), and when appetite happens to
be present in us, the one opinion bids us avoid the object, but appetite leads us towards it (for it can move
each of our bodily parts); so that it turns out that a man behaves incontinently under the influence (in a sense)
of a rule and an opinion, and of one not contrary in itself, but only incidentally-for the appetite is contrary,
not the opinion-to the right rule. It also follows that this is the reason why the lower animals are not
incontinent, viz. because they have no universal judgement but only imagination and memory of particulars.

The explanation of how the ignorance is dissolved and the incontinent man regains his knowledge, is the
same as in the case of the man drunk or asleep and is not peculiar to this condition; we must go to the
students of natural science for it. Now, the last premiss both being an opinion about a perceptible object, and
being what determines our actions this a man either has not when he is in the state of passion, or has it in the
sense in which having knowledge did not mean knowing but only talking, as a drunken man may utter the
verses of Empedocles. And because the last term is not universal nor equally an object of scientific
knowledge with the universal term, the position that Socrates sought to establish actually seems to result; for
it is not in the presence of what is thought to be knowledge proper that the affection of incontinence arises
(nor is it this that is 'dragged about' as a result of the state of passion), but in that of perceptual knowledge.

This must suffice as our answer to the question of action with and without knowledge, and how it is possible
to behave incontinently with knowledge.

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(2) We must next discuss whether there is any one who is incontinent without qualification, or all men who
are incontinent are so in a particular sense, and if there is, with what sort of objects he is concerned. That both
continent persons and persons of endurance, and incontinent and soft persons, are concerned with pleasures
and pains, is evident.

Now of the things that produce pleasure some are necessary, while others are worthy of choice in themselves
but admit of excess, the bodily causes of pleasure being necessary (by such I mean both those concerned with
food and those concerned with sexual intercourse, i.e. the bodily matters with which we defined
self-indulgence and temperance as being concerned), while the others are not necessary but worthy of choice
in themselves (e.g. victory, honour, wealth, and good and pleasant things of this sort). This being so, (a) those
who go to excess with reference to the latter, contrary to the right rule which is in themselves, are not called
incontinent simply, but incontinent with the qualification 'in respect of money, gain, honour, or anger',-not
simply incontinent, on the ground that they are different from incontinent people and are called incontinent
by reason of a resemblance. (Compare the case of Anthropos (Man), who won a contest at the Olympic
games; in his case the general definition of man differed little from the definition peculiar to him, but yet it
was different.) This is shown by the fact that incontinence either without qualification or in respect of some
particular bodily pleasure is blamed not only as a fault but as a kind of vice, while none of the people who are
incontinent in these other respects is so blamed.

But (b) of the people who are incontinent with respect to bodily enjoyments, with which we say the temperate
and the self-indulgent man are concerned, he who pursues the excesses of things pleasant-and shuns those of
things painful, of hunger and thirst and heat and cold and all the objects of touch and taste-not by choice but
contrary to his choice and his judgement, is called incontinent, not with the qualification 'in respect of this or
that', e.g. of anger, but just simply. This is confirmed by the fact that men are called 'soft' with regard to these
pleasures, but not with regard to any of the others. And for this reason we group together the incontinent and
the self-indulgent, the continent and the temperate man-but not any of these other types-because they are
concerned somehow with the same pleasures and pains; but though these are concerned with the same
objects, they are not similarly related to them, but some of them make a deliberate choice while the others do
not.

This is why we should describe as self-indulgent rather the man who without appetite or with but a slight
appetite pursues the excesses of pleasure and avoids moderate pains, than the man who does so because of his
strong appetites; for what would the former do, if he had in addition a vigorous appetite, and a violent pain at
the lack of the 'necessary' objects?

Now of appetites and pleasures some belong to the class of things generically noble and good-for some
pleasant things are by nature worthy of choice, while others are contrary to these, and others are intermediate,
to adopt our previous distinction-e.g. wealth, gain, victory, honour. And with reference to all objects whether
of this or of the intermediate kind men are not blamed for being affected by them, for desiring and loving
them, but for doing so in a certain way, i.e. for going to excess. (This is why all those who contrary to the rule
either are mastered by or pursue one of the objects which are naturally noble and good, e.g. those who busy
themselves more than they ought about honour or about children and parents, (are not wicked); for these too
are good, and those who busy themselves about them are praised; but yet there is an excess even in them-if
like Niobe one were to fight even against the gods, or were to be as much devoted to one's father as Satyrus
nicknamed 'the filial', who was thought to be very silly on this point.) There is no wickedness, then, with
regard to these objects, for the reason named, viz. because each of them is by nature a thing worthy of choice
for its own sake; yet excesses in respect of them are bad and to be avoided. Similarly there is no incontinence
with regard to them; for incontinence is not only to be avoided but is also a thing worthy of blame; but owing
to a similarity in the state of feeling people apply the name incontinence, adding in each case what it is in
respect of, as we may describe as a bad doctor or a bad actor one whom we should not call bad, simply. As,
then, in this case we do not apply the term without qualification because each of these conditions is no

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shadness but only analogous to it, so it is clear that in the other case also that alone must be taken to be
incontinence and continence which is concerned with the same objects as temperance and self-indulgence,
but we apply the term to anger by virtue of a resemblance; and this is why we say with a qualification
'incontinent in respect of anger' as we say 'incontinent in respect of honour, or of gain'.

(1) Some things are pleasant by nature, and of these (a) some are so without qualification, and (b) others are
so with reference to particular classes either of animals or of men; while (2) others are not pleasant by nature,
but (a) some of them become so by reason of injuries to the system, and (b) others by reason of acquired
habits, and (c) others by reason of originally bad natures. This being so, it is possible with regard to each of
the latter kinds to discover similar states of character to those recognized with regard to the former; I mean
(A) the brutish states, as in the case of the female who, they say, rips open pregnant women and devours the
infants, or of the things in which some of the tribes about the Black Sea that have gone savage are said to
delight-in raw meat or in human flesh, or in lending their children to one another to feast upon-or of the
story told of Phalaris.

These states are brutish, but (B) others arise as a result of disease (or, in some cases, of madness, as with the
man who sacrificed and ate his mother, or with the slave who ate the liver of his fellow), and others are
morbid states (C) resulting from custom, e.g. the habit of plucking out the hair or of gnawing the nails, or
even coals or earth, and in addition to these paederasty; for these arise in some by nature and in others, as in
those who have been the victims of lust from childhood, from habit.

Now those in whom nature is the cause of such a state no one would call incontinent, any more than one
would apply the epithet to women because of the passive part they play in copulation; nor would one apply it
to those who are in a morbid condition as a result of habit. To have these various types of habit is beyond the
limits of vice, as brutishness is too; for a man who has them to master or be mastered by them is not simple
(continence or) incontinence but that which is so by analogy, as the man who is in this condition in respect of
fits of anger is to be called incontinent in respect of that feeling but not incontinent simply. For every
excessive state whether of folly, of cowardice, of self-indulgence, or of bad temper, is either brutish or
morbid; the man who is by nature apt to fear everything, even the squeak of a mouse, is cowardly with a
brutish cowardice, while the man who feared a weasel did so in consequence of disease; and of foolish people
those who by nature are thoughtless and live by their senses alone are brutish, like some races of the distant
barbarians, while those who are so as a result of disease (e.g. of epilepsy) or of madness are morbid. Of these
characteristics it is possible to have some only at times, and not to be mastered by them. e.g. Phalaris may
have restrained a desire to eat the flesh of a child or an appetite for unnatural sexual pleasure; but it is also
possible to be mastered, not merely to have the feelings. Thus, as the wickedness which is on the human level
is called wickedness simply, while that which is not is called wickedness not simply but with the qualification
'brutish' or 'morbid', in the same way it is plain that some incontinence is brutish and some morbid, while
only that which corresponds to human self-indulgence is incontinence simply.

That incontinence and continence, then, are concerned only with the same objects as selfindulgence and
temperance and that what is concerned with other objects is a type distinct from incontinence, and called
incontinence by a metaphor and not simply, is plain.

That incontinence in respect of anger is less disgraceful than that in respect of the appetites is what we will
now proceed to see. (1) Anger seems to listen to argument to some extent, but to mishear it, as do hasty
servants who run out before they have heard the whole of what one says, and then muddle the order, or as
dogs bark if there is but a knock at the door, before looking to see if it is a friend; so anger by reason of the
warmth and hastiness of its nature, though it hears, does not hear an order, and springs to take revenge. For
argument or imagination informs us that we have been insulted or slighted, and anger, reasoning as it were
that anything like this must be fought against, boils up straightway; while appetite, if argument or perception
merely says that an object is pleasant, springs to the enjoyment of it. Therefore anger obeys the argument in a

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sense, but appetite does not. It is therefore more disgraceful; for the man who is incontinent in respect of
anger is in a sense conquered by argument, while the other is conquered by appetite and not by argument.

(2) Further, we pardon people more easily for following natural desires, since we pardon them more easily for
following such appetites as are common to all men, and in so far as they are common; now anger and bad
temper are more natural than the appetites for excess, i.e. for unnecessary objects. Take for instance the man
who defended himself on the charge of striking his father by saying 'yes, but he struck his father, and he
struck his, and' (pointing to his child) 'this boy will strike me when he is a man; it runs in the family'; or the
man who when he was being dragged along by his son bade him stop at the doorway, since he himself had
dragged his father only as far as that.

(2) Further, those who are more given to plotting against others are more criminal. Now a passionate man is
not given to plotting, nor is anger itself-it is open; but the nature of appetite is illustrated by what the poets
call Aphrodite, 'guile-weaving daughter of Cyprus', and by Homer's words about her 'embroidered girdle':

And the whisper of wooing is there,
Whose subtlety stealeth the wits of the wise, how prudent soe'er.

Therefore if this form of incontinence is more criminal and disgraceful than that in respect of anger, it is both
incontinence without qualification and in a sense vice.

(4) Further, no one commits wanton outrage with a feeling of pain, but every one who acts in anger acts with
pain, while the man who commits outrage acts with pleasure. If, then, those acts at which it is most just to be
angry are more criminal than others, the incontinence which is due to appetite is the more criminal; for there
is no wanton outrage involved in anger.

Plainly, then, the incontinence concerned with appetite is more disgraceful than that concerned with anger,
and continence and incontinence are concerned with bodily appetites and pleasures; but we must grasp the
differences among the latter themselves. For, as has been said at the beginning, some are human and natural
both in kind and in magnitude, others are brutish, and others are due to organic injuries and diseases. Only
with the first of these are temperance and self-indulgence concerned; this is why we call the lower animals
neither temperate nor self-indulgent except by a metaphor, and only if some one race of animals exceeds
another as a whole in wantonness, destructiveness, and omnivorous greed; these have no power of choice or
calculation, but they are departures from the natural norm, as, among men, madmen are. Now brutishness is a
less evil than vice, though more alarming; for it is not that the better part has been perverted, as in man,-they
have no better part. Thus it is like comparing a lifeless thing with a living in respect of badness; for the
badness of that which has no originative source of movement is always less hurtful, and reason is an
originative source. Thus it is like comparing injustice in the abstract with an unjust man. Each is in some
sense worse; for a bad man will do ten thousand times as much evil as a brute.

With regard to the pleasures and pains and appetites and aversions arising through touch and taste, to which
both self-indulgence and temperance were formerly narrowed down, it possible to be in such a state as to be
defeated even by those of them which most people master, or to master even those by which most people are
defeated; among these possibilities, those relating to pleasures are incontinence and continence, those relating
to pains softness and endurance. The state of most people is intermediate, even if they lean more towards the
worse states.

Now, since some pleasures are necessary while others are not, and are necessary up to a point while the
excesses of them are not, nor the deficiencies, and this is equally true of appetites and pains, the man who
pursues the excesses of things pleasant, or pursues to excess necessary objects, and does so by choice, for
their own sake and not at all for the sake of any result distinct from them, is self-indulgent; for such a man is

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of necessity unlikely to repent, and therefore incurable, since a man who cannot repent cannot be cured. The
man who is deficient in his pursuit of them is the opposite of self-indulgent; the man who is intermediate is
temperate. Similarly, there is the man who avoids bodily pains not because he is defeated by them but by
choice. (Of those who do not choose such acts, one kind of man is led to them as a result of the pleasure
involved, another because he avoids the pain arising from the appetite, so that these types differ from one
another. Now any one would think worse of a man with no appetite or with weak appetite were he to do
something disgraceful, than if he did it under the influence of powerful appetite, and worse of him if he struck
a blow not in anger than if he did it in anger; for what would he have done if he had been strongly affected?
This is why the self-indulgent man is worse than the incontinent.) of the states named, then, the latter is
rather a kind of softness; the former is self-indulgence. While to the incontinent man is opposed the
continent, to the soft is opposed the man of endurance; for endurance consists in resisting, while continence
consists in conquering, and resisting and conquering are different, as not being beaten is different from
winning; this is why continence is also more worthy of choice than endurance. Now the man who is defective
in respect of resistance to the things which most men both resist and resist successfully is soft and effeminate;
for effeminacy too is a kind of softness; such a man trails his cloak to avoid the pain of lifting it, and plays
the invalid without thinking himself wretched, though the man he imitates is a wretched man.

The case is similar with regard to continence and incontinence. For if a man is defeated by violent and
excessive pleasures or pains, there is nothing wonderful in that; indeed we are ready to pardon him if he has
resisted, as Theodectes' Philoctetes does when bitten by the snake, or Carcinus' Cercyon in the Alope, and as
people who try to restrain their laughter burst out into a guffaw, as happened to Xenophantus. But it is
surprising if a man is defeated by and cannot resist pleasures or pains which most men can hold out against,
when this is not due to heredity or disease, like the softness that is hereditary with the kings of the Scythians,
or that which distinguishes the female sex from the male.

The lover of amusement, too, is thought to be self-indulgent, but is really soft. For amusement is a
relaxation, since it is a rest from work; and the lover of amusement is one of the people who go to excess in
this.

Of incontinence one kind is impetuosity, another weakness. For some men after deliberating fail, owing to
their emotion, to stand by the conclusions of their deliberation, others because they have not deliberated are
led by their emotion; since some men (just as people who first tickle others are not tickled themselves), if
they have first perceived and seen what is coming and have first roused themselves and their calculative
faculty, are not defeated by their emotion, whether it be pleasant or painful. It is keen and excitable people
that suffer especially from the impetuous form of incontinence; for the former by reason of their quickness
and the latter by reason of the violence of their passions do not await the argument, because they are apt to
follow their imagination.

The self-indulgent man, as was said, is not apt to repent; for he stands by his choice; but incontinent man is
likely to repent. This is why the position is not as it was expressed in the formulation of the problem, but the
self indulgent man is incurable and the incontinent man curable; for wickedness is like a disease such as
dropsy or consumption, while incontinence is like epilepsy; the former is a permanent, the latter an
intermittent badness. And generally incontinence and vice are different in kind; vice is unconscious of itself,
incontinence is not (of incontinent men themselves, those who become temporarily beside themselves are
better than those who have the rational principle but do not abide by it, since the latter are defeated by a
weaker passion, and do not act without previous deliberation like the others); for the incontinent man is like
the people who get drunk quickly and on little wine, i.e. on less than most people.

Evidently, then, incontinence is not vice (though perhaps it is so in a qualified sense); for incontinence is
contrary to choice while vice is in accordance with choice; not but what they are similar in respect of the
actions they lead to; as in the saying of Demodocus about the Milesians, 'the Milesians are not without sense,

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but they do the things that senseless people do', so too incontinent people are not criminal, but they will do
criminal acts.

Now, since the incontinent man is apt to pursue, not on conviction, bodily pleasures that are excessive and
contrary to the right rule, while the self-indulgent man is convinced because he is the sort of man to pursue
them, it is on the contrary the former that is easily persuaded to change his mind, while the latter is not. For
virtue and vice respectively preserve and destroy the first principle, and in actions the final cause is the first
principle, as the hypotheses are in mathematics; neither in that case is it argument that teaches the first
principles, nor is it so here-virtue either natural or produced by habituation is what teaches right opinion
about the first principle. Such a man as this, then, is temperate; his contrary is the self-indulgent.

But there is a sort of man who is carried away as a result of passion and contrary to the right rule-a man
whom passion masters so that he does not act according to the right rule, but does not master to the extent of
making him ready to believe that he ought to pursue such pleasures without reserve; this is the incontinent
man, who is better than the self-indulgent man, and not bad without qualification; for the best thing in him,
the first principle, is preserved. And contrary to him is another kind of man, he who abides by his convictions
and is not carried away, at least as a result of passion. It is evident from these considerations that the latter is
a good state and the former a bad one.

Is the man continent who abides by any and every rule and any and every choice, or the man who abides by
the right choice, and is he incontinent who abandons any and every choice and any and every rule, or he who
abandons the rule that is not false and the choice that is right; this is how we put it before in our statement of
the problem. Or is it incidentally any and every choice but per se the true rule and the right choice by which
the one abides and the other does not? If any one chooses or pursues this for the sake of that, per se he
pursues and chooses the latter, but incidentally the former. But when we speak without qualification we mean
what is per se. Therefore in a sense the one abides by, and the other abandons, any and every opinion; but
without qualification, the true opinion.

There are some who are apt to abide by their opinion, who are called strong-headed, viz. those who are hard
to persuade in the first instance and are not easily persuaded to change; these have in them something like the
continent man, as the prodigal is in a way like the liberal man and the rash man like the confident man; but
they are different in many respects. For it is to passion and appetite that the one will not yield, since on
occasion the continent man will be easy to persuade; but it is to argument that the others refuse to yield, for
they do form appetites and many of them are led by their pleasures. Now the people who are strong-headed
are the opinionated, the ignorant, and the boorish-the opinionated being influenced by pleasure and pain; for
they delight in the victory they gain if they are not persuaded to change, and are pained if their decisions
become null and void as decrees sometimes do; so that they are liker the incontinent than the continent man.

But there are some who fail to abide by their resolutions, not as a result of incontinence, e.g. Neoptolemus in
Sophocles' Philoctetes; yet it was for the sake of pleasure that he did not stand fast-but a noble pleasure; for
telling the truth was noble to him, but he had been persuaded by Odysseus to tell the lie. For not every one
who does anything for the sake of pleasure is either self-indulgent or bad or incontinent, but he who does it
for a disgraceful pleasure.

Since there is also a sort of man who takes less delight than he should in bodily things, and does not abide by
the rule, he who is intermediate between him and the incontinent man is the continent man; for the
incontinent man fails to abide by the rule because he delights too much in them, and this man because he
delights in them too little; while the continent man abides by the rule and does not change on either account.
Now if continence is good, both the contrary states must be bad, as they actually appear to be; but because the
other extreme is seen in few people and seldom, as temperance is thought to be contrary only to
self-indulgence, so is continence to incontinence.

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Since many names are applied analogically, it is by analogy that we have come to speak of the 'continence'
the temperate man; for both the continent man and the temperate man are such as to do nothing contrary to
the rule for the sake of the bodily pleasures, but the former has and the latter has not bad appetites, and the
latter is such as not to feel pleasure contrary to the rule, while the former is such as to feel pleasure but not to
be led by it. And the incontinent and the self-indulgent man are also like another; they are different, but both
pursue bodily pleasures- the latter, however, also thinking that he ought to do so, while the former does not
think this.

Nor can the same man have practical wisdom and be incontinent; for it has been shown' that a man is at the
same time practically wise, and good in respect of character. Further, a man has practical wisdom not by
knowing only but by being able to act; but the incontinent man is unable to act-there is, however, nothing to
prevent a clever man from being incontinent; this is why it is sometimes actually thought that some people
have practical wisdom but are incontinent, viz. because cleverness and practical wisdom differ in the way we
have described in our first discussions, and are near together in respect of their reasoning, but differ in respect
of their purpose-nor yet is the incontinent man like the man who knows and is contemplating a truth, but like
the man who is asleep or drunk. And he acts willingly (for he acts in a sense with knowledge both of what he
does and of the end to which he does it), but is not wicked, since his purpose is good; so that he is
half-wicked. And he is not a criminal; for he does not act of malice aforethought; of the two types of
incontinent man the one does not abide by the conclusions of his deliberation, while the excitable man does
not deliberate at all. And thus the incontinent man like a city which passes all the right decrees and has good
laws, but makes no use of them, as in Anaxandrides' jesting remark,

The city willed it, that cares nought for laws;

but the wicked man is like a city that uses its laws, but has wicked laws to use.

Now incontinence and continence are concerned with that which is in excess of the state characteristic of
most men; for the continent man abides by his resolutions more and the incontinent man less than most men
can.

Of the forms of incontinence, that of excitable people is more curable than that of those who deliberate but do
not abide by their decisions, and those who are incontinent through habituation are more curable than those in
whom incontinence is innate; for it is easier to change a habit than to change one's nature; even habit is hard
to change just because it is like nature, as Evenus says:

I say that habit's but a long practice, friend,
And this becomes men's nature in the end.

We have now stated what continence, incontinence, endurance, and softness are, and how these states are
related to each other.

The study of pleasure and pain belongs to the province of the political philosopher; for he is the architect of
the end, with a view to which we call one thing bad and another good without qualification. Further, it is one
of our necessary tasks to consider them; for not only did we lay it down that moral virtue and vice are
concerned with pains and pleasures, but most people say that happiness involves pleasure; this is why the
blessed man is called by a name derived from a word meaning enjoyment.

Now (1) some people think that no pleasure is a good, either in itself or incidentally, since the good and
pleasure are not the same; (2) others think that some pleasures are good but that most are bad. (3) Again there
is a third view, that even if all pleasures are good, yet the best thing in the world cannot be pleasure. (1) The
reasons given for the view that pleasure is not a good at all are (a) that every pleasure is a perceptible process

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to a natural state, and that no process is of the same kind as its end, e.g. no process of building of the same
kind as a house, (b) A temperate man avoids pleasures, (c) A man of practical wisdom pursues what is free
from pain, not what is pleasant, (d) The pleasures are a hindrance to thought, and the more so the more one
delights in them, e.g. in sexual pleasure; for no one could think of anything while absorbed in this, (e) There
is no art of pleasure; but every good is the product of some art. (f) Children and the brutes pursue pleasures.
(2) The reasons for the view that not all pleasures are good are that (a) there are pleasures that are actually
base and objects of reproach, and (b) there are harmful pleasures; for some pleasant things are unhealthy. (3)
The reason for the view that the best thing in the world is not pleasure is that pleasure is not an end but a
process.

These are pretty much the things that are said. That it does not follow from these grounds that pleasure is not
a good, or even the chief good, is plain from the following considerations. (A) (a) First, since that which is
good may be so in either of two senses (one thing good simply and another good for a particular person),
natural constitutions and states of being, and therefore also the corresponding movements and processes, will
be correspondingly divisible. Of those which are thought to be bad some will be bad if taken without
qualification but not bad for a particular person, but worthy of his choice, and some will not be worthy of
choice even for a particular person, but only at a particular time and for a short period, though not without
qualification; while others are not even pleasures, but seem to be so, viz. all those which involve pain and
whose end is curative, e.g. the processes that go on in sick persons.

(b) Further, one kind of good being activity and another being state, the processes that restore us to our
natural state are only incidentally pleasant; for that matter the activity at work in the appetites for them is the
activity of so much of our state and nature as has remained unimpaired; for there are actually pleasures that
involve no pain or appetite (e.g. those of contemplation), the nature in such a case not being defective at all.
That the others are incidental is indicated by the fact that men do not enjoy the same pleasant objects when
their nature is in its settled state as they do when it is being replenished, but in the former case they enjoy the
things that are pleasant without qualification, in the latter the contraries of these as well; for then they enjoy
even sharp and bitter things, none of which is pleasant either by nature or without qualification. The states
they produce, therefore, are not pleasures naturally or without qualification; for as pleasant things differ, so
do the pleasures arising from them.

(c) Again, it is not necessary that there should be something else better than pleasure, as some say the end is
better than the process; for leasures are not processes nor do they all involve process-they are activities and
ends; nor do they arise when we are becoming something, but when we are exercising some faculty; and not
all pleasures have an end different from themselves, but only the pleasures of persons who are being led to
the perfecting of their nature. This is why it is not right to say that pleasure is perceptible process, but it
should rather be called activity of the natural state, and instead of 'perceptible' 'unimpeded'. It is thought by
some people to be process just because they think it is in the strict sense good; for they think that activity is
process, which it is not.

(B) The view that pleasures are bad because some pleasant things are unhealthy is like saying that healthy
things are bad because some healthy things are bad for money-making; both are bad in the respect
mentioned, but they are not bad for that reason-indeed, thinking itself is sometimes injurious to health.

Neither practical wisdom nor any state of being is impeded by the pleasure arising from it; it is foreign
pleasures that impede, for the pleasures arising from thinking and learning will make us think and learn all
the more.

(C) The fact that no pleasure is the product of any art arises naturally enough; there is no art of any other
activity either, but only of the corresponding faculty; though for that matter the arts of the perfumer and the
cook are thought to be arts of pleasure.

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(D) The arguments based on the grounds that the temperate man avoids pleasure and that the man of practical
wisdom pursues the painless life, and that children and the brutes pursue pleasure, are all refuted by the same
consideration. We have pointed out in what sense pleasures are good without qualification and in what sense
some are not good; now both the brutes and children pursue pleasures of the latter kind (and the man of
practical wisdom pursues tranquil freedom from that kind), viz. those which imply appetite and pain, i.e. the
bodily pleasures (for it is these that are of this nature) and the excesses of them, in respect of which the
self-indulgent man is self-indulent. This is why the temperate man avoids these pleasures; for even he has
pleasures of his own.

But further (E) it is agreed that pain is bad and to be avoided; for some pain is without qualification bad, and
other pain is bad because it is in some respect an impediment to us. Now the contrary of that which is to be
avoided, qua something to be avoided and bad, is good. Pleasure, then, is necessarily a good. For the answer
of Speusippus, that pleasure is contrary both to pain and to good, as the greater is contrary both to the less and
to the equal, is not successful; since he would not say that pleasure is essentially just a species of evil.

And (F) if certain pleasures are bad, that does not prevent the chief good from being some pleasure, just as
the chief good may be some form of knowledge though certain kinds of knowledge are bad. Perhaps it is even
necessary, if each disposition has unimpeded activities, that, whether the activity (if unimpeded) of all our
dispositions or that of some one of them is happiness, this should be the thing most worthy of our choice; and
this activity is pleasure. Thus the chief good would be some pleasure, though most pleasures might perhaps
be bad without qualification. And for this reason all men think that the happy life is pleasant and weave
pleasure into their ideal of happiness-and reasonably too; for no activity is perfect when it is impeded, and
happiness is a perfect thing; this is why the happy man needs the goods of the body and external goods, i.e.
those of fortune, viz. in order that he may not be impeded in these ways. Those who say that the victim on the
rack or the man who falls into great misfortunes is happy if he is good, are, whether they mean to or not,
talking nonsense. Now because we need fortune as well as other things, some people think good fortune the
same thing as happiness; but it is not that, for even good fortune itself when in excess is an impediment, and
perhaps should then be no longer called good fortune; for its limit is fixed by reference to happiness.

And indeed the fact that all things, both brutes and men, pursue pleasure is an indication of its being
somehow the chief good:

No voice is wholly lost that many peoples...

But since no one nature or state either is or is thought the best for all, neither do all pursue the same pleasure;
yet all pursue pleasure. And perhaps they actually pursue not the pleasure they think they pursue nor that
which they would say they pursue, but the same pleasure; for all things have by nature something divine in
them. But the bodily pleasures have appropriated the name both because we oftenest steer our course for
them and because all men share in them; thus because they alone are familiar, men think there are no others.

It is evident also that if pleasure, i.e. the activity of our faculties, is not a good, it will not be the case that the
happy man lives a pleasant life; for to what end should he need pleasure, if it is not a good but the happy man
may even live a painful life? For pain is neither an evil nor a good, if pleasure is not; why then should he
avoid it? Therefore, too, the life of the good man will not be pleasanter than that of any one else, if his
activities are not more pleasant.

(G) With regard to the bodily pleasures, those who say that some pleasures are very much to be chosen, viz.
the noble pleasures, but not the bodily pleasures, i.e. those with which the self-indulgent man is concerned,
must consider why, then, the contrary pains are bad. For the contrary of bad is good. Are the necessary
pleasures good in the sense in which even that which is not bad is good? Or are they good up to a point? Is it
that where you have states and processes of which there cannot be too much, there cannot be too much of the

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corresponding pleasure, and that where there can be too much of the one there can be too much of the other
also? Now there can be too much of bodily goods, and the bad man is bad by virtue of pursuing the excess,
not by virtue of pursuing the necessary pleasures (for all men enjoy in some way or other both dainty foods
and wines and sexual intercourse, but not all men do so as they ought). The contrary is the case with pain; for
he does not avoid the excess of it, he avoids it altogether; and this is peculiar to him, for the alternative to
excess of pleasure is not pain, except to the man who pursues this excess.

Since we should state not only the truth, but also the cause of error-for this contributes towards producing
conviction, since when a reasonable explanation is given of why the false view appears true, this tends to
produce belief in the true view-therefore we must state why the bodily pleasures appear the more worthy of
choice, (a) Firstly, then, it is because they expel pain; owing to the excesses of pain that men experience, they
pursue excessive and in general bodily pleasure as being a cure for the pain. Now curative agencies produce
intense feeling-which is the reason why they are pursued-because they show up against the contrary pain.
(Indeed pleasure is thought not to be good for these two reasons, as has been said, viz. that (a) some of them
are activities belonging to a bad nature-either congenital, as in the case of a brute, or due to habit, i.e. those
of bad men; while (b) others are meant to cure a defective nature, and it is better to be in a healthy state than
to be getting into it, but these arise during the process of being made perfect and are therefore only
incidentally good.) (b) Further, they are pursued because of their violence by those who cannot enjoy other
pleasures. (At all events they go out of their way to manufacture thirsts somehow for themselves. When these
are harmless, the practice is irreproachable; when they are hurtful, it is bad.) For they have nothing else to
enjoy, and, besides, a neutral state is painful to many people because of their nature. For the animal nature is
always in travail, as the students of natural science also testify, saying that sight and hearing are painful; but
we have become used to this, as they maintain. Similarly, while, in youth, people are, owing to the growth
that is going on, in a situation like that of drunken men, and youth is pleasant, on the other hand people of
excitable nature always need relief; for even their body is ever in torment owing to its special composition,
and they are always under the influence of violent desire; but pain is driven out both by the contrary pleasure,
and by any chance pleasure if it be strong; and for these reasons they become self-indulgent and bad. But the
pleasures that do not involve pains do not admit of excess; and these are among the things pleasant by nature
and not incidentally. By things pleasant incidentally I mean those that act as cures (for because as a result
people are cured, through some action of the part that remains healthy, for this reason the process is thought
pleasant); by things naturally pleasant I mean those that stimulate the action of the healthy nature.

There is no one thing that is always pleasant, because our nature is not simple but there is another element in
us as well, inasmuch as we are perishable creatures, so that if the one element does something, this is
unnatural to the other nature, and when the two elements are evenly balanced, what is done seems neither
painful nor pleasant; for if the nature of anything were simple, the same action would always be most
pleasant to it. This is why God always enjoys a single and simple pleasure; for there is not only an activity of
movement but an activity of immobility, and pleasure is found more in rest than in movement. But 'change in
all things is sweet', as the poet says, because of some vice; for as it is the vicious man that is changeable, so
the nature that needs change is vicious; for it is not simple nor good.

We have now discussed continence and incontinence, and pleasure and pain, both what each is and in what
sense some of them are good and others bad; it remains to speak of friendship.

BOOK VIII

AFTER what we have said, a discussion of friendship would naturally follow, since it is a virtue or implies
virtue, and is besides most necessary with a view to living. For without friends no one would choose to live,
though he had all other goods; even rich men and those in possession of office and of dominating power are
thought to need friends most of all; for what is the use of such prosperity without the opportunity of
beneficence, which is exercised chiefly and in its most laudable form towards friends? Or how can prosperity

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be guarded and preserved without friends? The greater it is, the more exposed is it to risk. And in poverty and
in other misfortunes men think friends are the only refuge. It helps the young, too, to keep from error; it aids
older people by ministering to their needs and supplementing the activities that are failing from weakness;
those in the prime of life it stimulates to noble actions-'two going together'-for with friends men are more
able both to think and to act. Again, parent seems by nature to feel it for offspring and offspring for parent,
not only among men but among birds and among most animals; it is felt mutually by members of the same
race, and especially by men, whence we praise lovers of their fellowmen. We may even in our travels how
near and dear every man is to every other. Friendship seems too to hold states together, and lawgivers to care
more for it than for justice; for unanimity seems to be something like friendship, and this they aim at most of
all, and expel faction as their worst enemy; and when men are friends they have no need of justice, while
when they are just they need friendship as well, and the truest form of justice is thought to be a friendly
quality.

But it is not only necessary but also noble; for we praise those who love their friends, and it is thought to be a
fine thing to have many friends; and again we think it is the same people that are good men and are friends.

Not a few things about friendship are matters of debate. Some define it as a kind of likeness and say like
people are friends, whence come the sayings 'like to like', 'birds of a feather flock together', and so on; others
on the contrary say 'two of a trade never agree'. On this very question they inquire for deeper and more
physical causes, Euripides saying that 'parched earth loves the rain, and stately heaven when filled with rain
loves to fall to earth', and Heraclitus that 'it is what opposes that helps' and 'from different tones comes the
fairest tune' and 'all things are produced through strife'; while Empedocles, as well as others, expresses the
opposite view that like aims at like. The physical problems we may leave alone (for they do not belong to the
present inquiry); let us examine those which are human and involve character and feeling, e.g. whether
friendship can arise between any two people or people cannot be friends if they are wicked, and whether there
is one species of friendship or more than one. Those who think there is only one because it admits of degrees
have relied on an inadequate indication; for even things different in species admit of degree. We have
discussed this matter previously.

The kinds of friendship may perhaps be cleared up if we first come to know the object of love. For not
everything seems to be loved but only the lovable, and this is good, pleasant, or useful; but it would seem to
be that by which some good or pleasure is produced that is useful, so that it is the good and the useful that are
lovable as ends. Do men love, then, the good, or what is good for them? These sometimes clash. So too with
regard to the pleasant. Now it is thought that each loves what is good for himself, and that the good is without
qualification lovable, and what is good for each man is lovable for him; but each man loves not what is good
for him but what seems good. This however will make no difference; we shall just have to say that this is 'that
which seems lovable'. Now there are three grounds on which people love; of the love of lifeless objects we do
not use the word 'friendship'; for it is not mutual love, nor is there a wishing of good to the other (for it would
surely be ridiculous to wish wine well; if one wishes anything for it, it is that it may keep, so that one may
have it oneself); but to a friend we say we ought to wish what is good for his sake. But to those who thus
wish good we ascribe only goodwill, if the wish is not reciprocated; goodwill when it is reciprocal being
friendship. Or must we add 'when it is recognized'? For many people have goodwill to those whom they have
not seen but judge to be good or useful; and one of these might return this feeling. These people seem to bear
goodwill to each other; but how could one call them friends when they do not know their mutual feelings? To
be friends, then, the must be mutually recognized as bearing goodwill and wishing well to each other for one
of the aforesaid reasons.

Now these reasons differ from each other in kind; so, therefore, do the corresponding forms of love and
friendship. There are therefore three kinds of friendship, equal in number to the things that are lovable; for
with respect to each there is a mutual and recognized love, and those who love each other wish well to each
other in that respect in which they love one another. Now those who love each other for their utility do not

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love each other for themselves but in virtue of some good which they get from each other. So too with those
who love for the sake of pleasure; it is not for their character that men love ready-witted people, but because
they find them pleasant. Therefore those who love for the sake of utility love for the sake of what is good for
themselves, and those who love for the sake of pleasure do so for the sake of what is pleasant to themselves,
and not in so far as the other is the person loved but in so far as he is useful or pleasant. And thus these
friendships are only incidental; for it is not as being the man he is that the loved person is loved, but as
providing some good or pleasure. Such friendships, then, are easily dissolved, if the parties do not remain like
themselves; for if the one party is no longer pleasant or useful the other ceases to love him.

Now the useful is not permanent but is always changing. Thus when the motive of the friendship is done
away, the friendship is dissolved, inasmuch as it existed only for the ends in question. This kind of friendship
seems to exist chiefly between old people (for at that age people pursue not the pleasant but the useful) and,
of those who are in their prime or young, between those who pursue utility. And such people do not live
much with each other either; for sometimes they do not even find each other pleasant; therefore they do not
need such companionship unless they are useful to each other; for they are pleasant to each other only in so
far as they rouse in each other hopes of something good to come. Among such friendships people also class
the friendship of a host and guest. On the other hand the friendship of young people seems to aim at pleasure;
for they live under the guidance of emotion, and pursue above all what is pleasant to themselves and what is
immediately before them; but with increasing age their pleasures become different. This is why they quickly
become friends and quickly cease to be so; their friendship changes with the object that is found pleasant, and
such pleasure alters quickly. Young people are amorous too; for the greater part of the friendship of love
depends on emotion and aims at pleasure; this is why they fall in love and quickly fall out of love, changing
often within a single day. But these people do wish to spend their days and lives together; for it is thus that
they attain the purpose of their friendship.

Perfect friendship is the friendship of men who are good, and alike in virtue; for these wish well alike to each
other qua good, and they are good themselves. Now those who wish well to their friends for their sake are
most truly friends; for they do this by reason of own nature and not incidentally; therefore their friendship
lasts as long as they are good-and goodness is an enduring thing. And each is good without qualification and
to his friend, for the good are both good without qualification and useful to each other. So too they are
pleasant; for the good are pleasant both without qualification and to each other, since to each his own
activities and others like them are pleasurable, and the actions of the good are the same or like. And such a
friendship is as might be expected permanent, since there meet in it all the qualities that friends should have.
For all friendship is for the sake of good or of pleasure-good or pleasure either in the abstract or such as will
be enjoyed by him who has the friendly feeling-and is based on a certain resemblance; and to a friendship of
good men all the qualities we have named belong in virtue of the nature of the friends themselves; for in the
case of this kind of friendship the other qualities also are alike in both friends, and that which is good without
qualification is also without qualification pleasant, and these are the most lovable qualities. Love and
friendship therefore are found most and in their best form between such men.

But it is natural that such friendships should be infrequent; for such men are rare. Further, such friendship
requires time and familiarity; as the proverb says, men cannot know each other till they have 'eaten salt
together'; nor can they admit each other to friendship or be friends till each has been found lovable and been
trusted by each. Those who quickly show the marks of friendship to each other wish to be friends, but are not
friends unless they both are lovable and know the fact; for a wish for friendship may arise quickly, but
friendship does not.

This kind of friendship, then, is perfect both in respect of duration and in all other respects, and in it each gets
from each in all respects the same as, or something like what, he gives; which is what ought to happen
between friends. Friendship for the sake of pleasure bears a resemblance to this kind; for good people too are
pleasant to each other. So too does friendship for the sake of utility; for the good are also useful to each other.

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Among men of these inferior sorts too, friendships are most permanent when the friends get the same thing
from each other (e.g. pleasure), and not only that but also from the same source, as happens between
readywitted people, not as happens between lover and beloved. For these do not take pleasure in the same
things, but the one in seeing the beloved and the other in receiving attentions from his lover; and when the
bloom of youth is passing the friendship sometimes passes too (for the one finds no pleasure in the sight of
the other, and the other gets no attentions from the first); but many lovers on the other hand are constant, if
familiarity has led them to love each other's characters, these being alike. But those who exchange not
pleasure but utility in their amour are both less truly friends and less constant. Those who are friends for the
sake of utility part when the advantage is at an end; for they were lovers not of each other but of profit.

For the sake of pleasure or utility, then, even bad men may be friends of each other, or good men of bad, or
one who is neither good nor bad may be a friend to any sort of person, but for their own sake clearly only
good men can be friends; for bad men do not delight in each other unless some advantage come of the
relation.

The friendship of the good too and this alone is proof against slander; for it is not easy to trust any one talk
about a man who has long been tested by oneself; and it is among good men that trust and the feeling that 'he
would never wrong me' and all the other things that are demanded in true friendship are found. In the other
kinds of friendship, however, there is nothing to prevent these evils arising. For men apply the name of
friends even to those whose motive is utility, in which sense states are said to be friendly (for the alliances of
states seem to aim at advantage), and to those who love each other for the sake of pleasure, in which sense
children are called friends. Therefore we too ought perhaps to call such people friends, and say that there are
several kinds of friendship-firstly and in the proper sense that of good men qua good, and by analogy the
other kinds; for it is in virtue of something good and something akin to what is found in true friendship that
they are friends, since even the pleasant is good for the lovers of pleasure. But these two kinds of friendship
are not often united, nor do the same people become friends for the sake of utility and of pleasure; for things
that are only incidentally connected are not often coupled together.

Friendship being divided into these kinds, bad men will be friends for the sake of pleasure or of utility, being
in this respect like each other, but good men will be friends for their own sake, i.e. in virtue of their goodness.
These, then, are friends without qualification; the others are friends incidentally and through a resemblance to
these.

As in regard to the virtues some men are called good in respect of a state of character, others in respect of an
activity, so too in the case of friendship; for those who live together delight in each other and confer benefits
on each other, but those who are asleep or locally separated are not performing, but are disposed to perform,
the activities of friendship; distance does not break off the friendship absolutely, but only the activity of it.
But if the absence is lasting, it seems actually to make men forget their friendship; hence the saying 'out of
sight, out of mind'. Neither old people nor sour people seem to make friends easily; for there is little that is
pleasant in them, and no one can spend his days with one whose company is painful, or not pleasant, since
nature seems above all to avoid the painful and to aim at the pleasant. Those, however, who approve of each
other but do not live together seem to be well-disposed rather than actual friends. For there is nothing so
characteristic of friends as living together (since while it people who are in need that desire benefits, even
those who are supremely happy desire to spend their days together; for solitude suits such people least of all);
but people cannot live together if they are not pleasant and do not enjoy the same things, as friends who are
companions seem to do.

The truest friendship, then, is that of the good, as we have frequently said; for that which is without
qualification good or pleasant seems to be lovable and desirable, and for each person that which is good or
pleasant to him; and the good man is lovable and desirable to the good man for both these reasons. Now it
looks as if love were a feeling, friendship a state of character; for love may be felt just as much towards

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lifeless things, but mutual love involves choice and choice springs from a state of character; and men wish
well to those whom they love, for their sake, not as a result of feeling but as a result of a state of character.
And in loving a friend men love what is good for themselves; for the good man in becoming a friend becomes
a good to his friend. Each, then, both loves what is good for himself, and makes an equal return in goodwill
and in pleasantness; for friendship is said to be equality, and both of these are found most in the friendship of
the good.

Between sour and elderly people friendship arises less readily, inasmuch as they are less good-tempered and
enjoy companionship less; for these are thou to be the greatest marks of friendship productive of it. This is
why, while men become friends quickly, old men do not; it is because men do not become friends with those
in whom they do not delight; and similarly sour people do not quickly make friends either. But such men may
bear goodwill to each other; for they wish one another well and aid one another in need; but they are hardly
friends because they do not spend their days together nor delight in each other, and these are thought the
greatest marks of friendship.

One cannot be a friend to many people in the sense of having friendship of the perfect type with them, just as
one cannot be in love with many people at once (for love is a sort of excess of feeling, and it is the nature of
such only to be felt towards one person); and it is not easy for many people at the same time to please the
same person very greatly, or perhaps even to be good in his eyes. One must, too, acquire some experience of
the other person and become familiar with him, and that is very hard. But with a view to utility or pleasure it
is possible that many people should please one; for many people are useful or pleasant, and these services
take little time.

Of these two kinds that which is for the sake of pleasure is the more like friendship, when both parties get the
same things from each other and delight in each other or in the things, as in the friendships of the young; for
generosity is more found in such friendships. Friendship based on utility is for the commercially minded.
People who are supremely happy, too, have no need of useful friends, but do need pleasant friends; for they
wish to live with some one and, though they can endure for a short time what is painful, no one could put up
with it continuously, nor even with the Good itself if it were painful to him; this is why they look out for
friends who are pleasant. Perhaps they should look out for friends who, being pleasant, are also good, and
good for them too; for so they will have all the characteristics that friends should have.

People in positions of authority seem to have friends who fall into distinct classes; some people are useful to
them and others are pleasant, but the same people are rarely both; for they seek neither those whose
pleasantness is accompanied by virtue nor those whose utility is with a view to noble objects, but in their
desire for pleasure they seek for ready-witted people, and their other friends they choose as being clever at
doing what they are told, and these characteristics are rarely combined. Now we have said that the good man
is at the same time pleasant and useful; but such a man does not become the friend of one who surpasses him
in station, unless he is surpassed also in virtue; if this is not so, he does not establish equality by being
proportionally exceeded in both respects. But people who surpass him in both respects are not so easy to find.

However that may be, the aforesaid friendships involve equality; for the friends get the same things from one
another and wish the same things for one another, or exchange one thing for another, e.g. pleasure for utility;
we have said, however, that they are both less truly friendships and less permanent.

But it is from their likeness and their unlikeness to the same thing that they are thought both to be and not to
be friendships. It is by their likeness to the friendship of virtue that they seem to be friendships (for one of
them involves pleasure and the other utility, and these characteristics belong to the friendship of virtue as
well); while it is because the friendship of virtue is proof against slander and permanent, while these quickly
change (besides differing from the former in many other respects), that they appear not to be friendships; i.e.
it is because of their unlikeness to the friendship of virtue.

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But there is another kind of friendship, viz. that which involves an inequality between the parties, e.g. that of
father to son and in general of elder to younger, that of man to wife and in general that of ruler to subject.
And these friendships differ also from each other; for it is not the same that exists between parents and
children and between rulers and subjects, nor is even that of father to son the same as that of son to father, nor
that of husband to wife the same as that of wife to husband. For the virtue and the function of each of these is
different, and so are the reasons for which they love; the love and the friendship are therefore different also.
Each party, then, neither gets the same from the other, nor ought to seek it; but when children render to
parents what they ought to render to those who brought them into the world, and parents render what they
should to their children, the friendship of such persons will be abiding and excellent. In all friendships
implying inequality the love also should be proportional, i.e. the better should be more loved than he loves,
and so should the more useful, and similarly in each of the other cases; for when the love is in proportion to
the merit of the parties, then in a sense arises equality, which is certainly held to be characteristic of
friendship.

But equality does not seem to take the same form in acts of justice and in friendship; for in acts of justice
what is equal in the primary sense is that which is in proportion to merit, while quantitative equality is
secondary, but in friendship quantitative equality is primary and proportion to merit secondary. This becomes
clear if there is a great interval in respect of virtue or vice or wealth or anything else between the parties; for
then they are no longer friends, and do not even expect to be so. And this is most manifest in the case of the
gods; for they surpass us most decisively in all good things. But it is clear also in the case of kings; for with
them, too, men who are much their inferiors do not expect to be friends; nor do men of no account expect to
be friends with the best or wisest men. In such cases it is not possible to define exactly up to what point
friends can remain friends; for much can be taken away and friendship remain, but when one party is
removed to a great distance, as God is, the possibility of friendship ceases. This is in fact the origin of the
question whether friends really wish for their friends the greatest goods, e.g. that of being gods; since in that
case their friends will no longer be friends to them, and therefore will not be good things for them (for friends
are good things). The answer is that if we were right in saying that friend wishes good to friend for his sake,
his friend must remain the sort of being he is, whatever that may be; therefore it is for him oily so long as he
remains a man that he will wish the greatest goods. But perhaps not all the greatest goods; for it is for himself
most of all that each man wishes what is good.

Most people seem, owing to ambition, to wish to be loved rather than to love; which is why most men love
flattery; for the flatterer is a friend in an inferior position, or pretends to be such and to love more than he is
loved; and being loved seems to be akin to being honoured, and this is what most people aim at. But it seems
to be not for its own sake that people choose honour, but incidentally. For most people enjoy being honoured
by those in positions of authority because of their hopes (for they think that if they want anything they will
get it from them; and therefore they delight in honour as a token of favour to come); while those who desire
honour from good men, and men who know, are aiming at confirming their own opinion of themselves; they
delight in honour, therefore, because they believe in their own goodness on the strength of the judgement of
those who speak about them. In being loved, on the other hand, people delight for its own sake; whence it
would seem to be better than being honoured, and friendship to be desirable in itself. But it seems to lie in
loving rather than in being loved, as is indicated by the delight mothers take in loving; for some mothers hand
over their children to be brought up, and so long as they know their fate they love them and do not seek to be
loved in return (if they cannot have both), but seem to be satisfied if they see them prospering; and they
themselves love their children even if these owing to their ignorance give them nothing of a mother's due.
Now since friendship depends more on loving, and it is those who love their friends that are praised, loving
seems to be the characteristic virtue of friends, so that it is only those in whom this is found in due measure
that are lasting friends, and only their friendship that endures.

It is in this way more than any other that even unequals can be friends; they can be equalized. Now equality
and likeness are friendship, and especially the likeness of those who are like in virtue; for being steadfast in

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themselves they hold fast to each other, and neither ask nor give base services, but (one may say) even
prevent them; for it is characteristic of good men neither to go wrong themselves nor to let their friends do so.
But wicked men have no steadfastness (for they do not remain even like to themselves), but become friends
for a short time because they delight in each other's wickedness. Friends who are useful or pleasant last
longer; i.e. as long as they provide each other with enjoyments or advantages. Friendship for utility's sake
seems to be that which most easily exists between contraries, e.g. between poor and rich, between ignorant
and learned; for what a man actually lacks he aims at, and one gives something else in return. But under this
head, too, might bring lover and beloved, beautiful and ugly. This is why lovers sometimes seem ridiculous,
when they demand to be loved as they love; if they are equally lovable their claim can perhaps be justified,
but when they have nothing lovable about them it is ridiculous. Perhaps, however, contrary does not even aim
at contrary by its own nature, but only incidentally, the desire being for what is intermediate; for that is what
is good, e.g. it is good for the dry not to become wet but to come to the intermediate state, and similarly with
the hot and in all other cases. These subjects we may dismiss; for they are indeed somewhat foreign to our
inquiry.

Friendship and justice seem, as we have said at the outset of our discussion, to be concerned with the same
objects and exhibited between the same persons. For in every community there is thought to be some form of
justice, and friendship too; at least men address as friends their fellow-voyagers and fellowsoldiers, and so
too those associated with them in any other kind of community. And the extent of their association is the
extent of their friendship, as it is the extent to which justice exists between them. And the proverb 'what
friends have is common property' expresses the truth; for friendship depends on community. Now brothers
and comrades have all things in common, but the others to whom we have referred have definite things in
common-some more things, others fewer; for of friendships, too, some are more and others less truly
friendships. And the claims of justice differ too; the duties of parents to children, and those of brothers to
each other are not the same, nor those of comrades and those of fellow-citizens, and so, too, with the other
kinds of friendship. There is a difference, therefore, also between the acts that are unjust towards each of
these classes of associates, and the injustice increases by being exhibited towards those who are friends in a
fuller sense; e.g. it is a more terrible thing to defraud a comrade than a fellow-citizen, more terrible not to
help a brother than a stranger, and more terrible to wound a father than any one else. And the demands of
justice also seem to increase with the intensity of the friendship, which implies that friendship and justice
exist between the same persons and have an equal extension.

Now all forms of community are like parts of the political community; for men journey together with a view
to some particular advantage, and to provide something that they need for the purposes of life; and it is for the
sake of advantage that the political community too seems both to have come together originally and to
endure, for this is what legislators aim at, and they call just that which is to the common advantage. Now the
other communities aim at advantage bit by bit, e.g. sailors at what is advantageous on a voyage with a view to
making money or something of the kind, fellow-soldiers at what is advantageous in war, whether it is wealth
or victory or the taking of a city that they seek, and members of tribes and demes act similarly (Some
communities seem to arise for the sake or pleasure, viz. religious guilds and social clubs; for these exist
respectively for the sake of offering sacrifice and of companionship. But all these seem to fall under the
political community; for it aims not at present advantage but at what is advantageous for life as a whole),
offering sacrifices and arranging gatherings for the purpose, and assigning honours to the gods, and providing
pleasant relaxations for themselves. For the ancient sacrifices and gatherings seem to take place after the
harvest as a sort of firstfruits, because it was at these seasons that people had most leisure. All the
communities, then, seem to be parts of the political community; and the particular kinds friendship will
correspond to the particular kinds of community.

There are three kinds of constitution, and an equal number of deviation-forms — perversions, as it were, of
them. The constitutions are monarchy, aristocracy, and thirdly that which is based on a property qualification,
which it seems appropriate to call timocratic, though most people are wont to call it polity. The best of these

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is monarchy, the worst timocracy. The deviation from monarchy is tyrany; for both are forms of one-man
rule, but there is the greatest difference between them; the tyrant looks to his own advantage, the king to that
of his subjects. For a man is not a king unless he is sufficient to himself and excels his subjects in all good
things; and such a man needs nothing further; therefore he will not look to his own interests but to those of
his subjects; for a king who is not like that would be a mere titular king. Now tyranny is the very contrary of
this; the tyrant pursues his own good. And it is clearer in the case of tyranny that it is the worst
deviation-form; but it is the contrary of the best that is worst. Monarchy passes over into tyranny; for tyranny
is the evil form of one-man rule and the bad king becomes a tyrant. Aristocracy passes over into oligarchy by
the badness of the rulers, who distribute contrary to equity what belongs to the city-all or most of the good
things to themselves, and office always to the same people, paying most regard to wealth; thus the rulers are
few and are bad men instead of the most worthy. Timocracy passes over into democracy; for these are
coterminous, since it is the ideal even of timocracy to be the rule of the majority, and all who have the
property qualification count as equal. Democracy is the least bad of the deviations; for in its case the form of
constitution is but a slight deviation. These then are the changes to which constitutions are most subject; for
these are the smallest and easiest transitions.

One may find resemblances to the constitutions and, as it were, patterns of them even in households. For the
association of a father with his sons bears the form of monarchy, since the father cares for his children; and
this is why Homer calls Zeus 'father'; it is the ideal of monarchy to be paternal rule. But among the Persians
the rule of the father is tyrannical; they use their sons as slaves. Tyrannical too is the rule of a master over
slaves; for it is the advantage of the master that is brought about in it. Now this seems to be a correct form of
government, but the Persian type is perverted; for the modes of rule appropriate to different relations are
diverse. The association of man and wife seems to be aristocratic; for the man rules in accordance with his
worth, and in those matters in which a man should rule, but the matters that befit a woman he hands over to
her. If the man rules in everything the relation passes over into oligarchy; for in doing so he is not acting in
accordance with their respective worth, and not ruling in virtue of his superiority. Sometimes, however,
women rule, because they are heiresses; so their rule is not in virtue of excellence but due to wealth and
power, as in oligarchies. The association of brothers is like timocracy; for they are equal, except in so far as
they differ in age; hence if they differ much in age, the friendship is no longer of the fraternal type.
Democracy is found chiefly in masterless dwellings (for here every one is on an equality), and in those in
which the ruler is weak and every one has licence to do as he pleases.

Each of the constitutions may be seen to involve friendship just in so far as it involves justice. The friendship
between a king and his subjects depends on an excess of benefits conferred; for he confers benefits on his
subjects if being a good man he cares for them with a view to their well-being, as a shepherd does for his
sheep (whence Homer called Agamemnon 'shepherd of the peoples'). Such too is the friendship of a father,
though this exceeds the other in the greatness of the benefits conferred; for he is responsible for the existence
of his children, which is thought the greatest good, and for their nurture and upbringing.

These things are ascribed to ancestors as well. Further, by nature a father tends to rule over his sons,
ancestors over descendants, a king over his subjects. These friendships imply superiority of one party over
the other, which is why ancestors are honoured. The justice therefore that exists between persons so related is
not the same on both sides but is in every case proportioned to merit; for that is true of the friendship as well.
The friendship of man and wife, again, is the same that is found in an aristocracy; for it is in accordance with
virtue the better gets more of what is good, and each gets what befits him; and so, too, with the justice in
these relations. The friendship of brothers is like that of comrades; for they are equal and of like age, and
such persons are for the most part like in their feelings and their character. Like this, too, is the friendship
appropriate to timocratic government; for in such a constitution the ideal is for the citizens to be equal and
fair; therefore rule is taken in turn, and on equal terms; and the friendship appropriate here will correspond.

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But in the deviation-forms, as justice hardly exists, so too does friendship. It exists least in the worst form; in
tyranny there is little or no friendship. For where there is nothing common to ruler and ruled, there is not
friendship either, since there is not justice; e.g. between craftsman and tool, soul and body, master and slave;
the latter in each case is benefited by that which uses it, but there is no friendship nor justice towards lifeless
things. But neither is there friendship towards a horse or an ox, nor to a slave qua slave. For there is nothing
common to the two parties; the slave is a living tool and the tool a lifeless slave. Qua slave then, one cannot
be friends with him. But qua man one can; for there seems to be some justice between any man and any other
who can share in a system of law or be a party to an agreement; therefore there can also be friendship with
him in so far as he is a man. Therefore while in tyrannies friendship and justice hardly exist, in democracies
they exist more fully; for where the citizens are equal they have much in common.

Every form of friendship, then, involves association, as has been said. One might, however, mark off from the
rest both the friendship of kindred and that of comrades. Those of fellow-citizens, fellow-tribesmen,
fellow-voyagers, and the like are more like mere friendships of association; for they seem to rest on a sort of
compact. With them we might class the friendship of host and guest. The friendship of kinsmen itself, while
it seems to be of many kinds, appears to depend in every case on parental friendship; for parents love their
children as being a part of themselves, and children their parents as being something originating from them.
Now (1) arents know their offspring better than there children know that they are their children, and (2) the
originator feels his offspring to be his own more than the offspring do their begetter; for the product belongs
to the producer (e.g. a tooth or hair or anything else to him whose it is), but the producer does not belong to
the product, or belongs in a less degree. And (3) the length of time produces the same result; parents love
their children as soon as these are born, but children love their parents only after time has elapsed and they
have acquired understanding or the power of discrimination by the senses. From these considerations it is also
plain why mothers love more than fathers do. Parents, then, love their children as themselves (for their issue
are by virtue of their separate existence a sort of other selves), while children love their parents as being born
of them, and brothers love each other as being born of the same parents; for their identity with them makes
them identical with each other (which is the reason why people talk of 'the same blood', 'the same stock', and
so on). They are, therefore, in a sense the same thing, though in separate individuals. Two things that
contribute greatly to friendship are a common upbringing and similarity of age; for 'two of an age take to
each other', and people brought up together tend to be comrades; whence the friendship of brothers is akin to
that of comrades. And cousins and other kinsmen are bound up together by derivation from brothers, viz. by
being derived from the same parents. They come to be closer together or farther apart by virtue of the
nearness or distance of the original ancestor.

The friendship of children to parents, and of men to gods, is a relation to them as to something good and
superior; for they have conferred the greatest benefits, since they are the causes of their being and of their
nourishment, and of their education from their birth; and this kind of friendship possesses pleasantness and
utility also, more than that of strangers, inasmuch as their life is lived more in common. The friendship of
brothers has the characteristics found in that of comrades (and especially when these are good), and in
general between people who are like each other, inasmuch as they belong more to each other and start with a
love for each other from their very birth, and inasmuch as those born of the same parents and brought up
together and similarly educated are more akin in character; and the test of time has been applied most fully
and convincingly in their case.

Between other kinsmen friendly relations are found in due proportion. Between man and wife friendship
seems to exist by nature; for man is naturally inclined to form couples-even more than to form cities,
inasmuch as the household is earlier and more necessary than the city, and reproduction is more common to
man with the animals. With the other animals the union extends only to this point, but human beings live
together not only for the sake of reproduction but also for the various purposes of life; for from the start the
functions are divided, and those of man and woman are different; so they help each other by throwing their
peculiar gifts into the common stock. It is for these reasons that both utility and pleasure seem to be found in

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this kind of friendship. But this friendship may be based also on virtue, if the parties are good; for each has its
own virtue and they will delight in the fact. And children seem to be a bond of union (which is the reason
why childless people part more easily); for children are a good common to both and what is common holds
them together.

How man and wife and in general friend and friend ought mutually to behave seems to be the same question
as how it is just for them to behave; for a man does not seem to have the same duties to a friend, a stranger, a
comrade, and a schoolfellow.

There are three kinds of friendship, as we said at the outset of our inquiry, and in respect of each some are
friends on an equality and others by virtue of a superiority (for not only can equally good men become friends
but a better man can make friends with a worse, and similarly in friendships of pleasure or utility the friends
may be equal or unequal in the benefits they confer). This being so, equals must effect the required
equalization on a basis of equality in love and in all other respects, while unequals must render what is in
proportion to their superiority or inferiority. Complaints and reproaches arise either only or chiefly in the
friendship of utility, and this is only to be expected. For those who are friends on the ground of virtue are
anxious to do well by each other (since that is a mark of virtue and of friendship), and between men who are
emulating each other in this there cannot be complaints or quarrels; no one is offended by a man who loves
him and does well by him-if he is a person of nice feeling he takes his revenge by doing well by the other.
And the man who excels the other in the services he renders will not complain of his friend, since he gets
what he aims at; for each man desires what is good. Nor do complaints arise much even in friendships of
pleasure; for both get at the same time what they desire, if they enjoy spending their time together; and even a
man who complained of another for not affording him pleasure would seem ridiculous, since it is in his power
not to spend his days with him.

But the friendship of utility is full of complaints; for as they use each other for their own interests they always
want to get the better of the bargain, and think they have got less than they should, and blame their partners
because they do not get all they 'want and deserve'; and those who do well by others cannot help them as
much as those whom they benefit want.

Now it seems that, as justice is of two kinds, one unwritten and the other legal, one kind of friendship of
utility is moral and the other legal. And so complaints arise most of all when men do not dissolve the relation
in the spirit of the same type of friendship in which they contracted it. The legal type is that which is on fixed
terms; its purely commercial variety is on the basis of immediate payment, while the more liberal variety
allows time but stipulates for a definite quid pro quo. In this variety the debt is clear and not ambiguous, but
in the postponement it contains an element of friendliness; and so some states do not allow suits arising out of
such agreements, but think men who have bargained on a basis of credit ought to accept the consequences.
The moral type is not on fixed terms; it makes a gift, or does whatever it does, as to a friend; but one expects
to receive as much or more, as having not given but lent; and if a man is worse off when the relation is
dissolved than he was when it was contracted he will complain. This happens because all or most men, while
they wish for what is noble, choose what is advantageous; now it is noble to do well by another without a
view to repayment, but it is the receiving of benefits that is advantageous. Therefore if we can we should
return the equivalent of what we have received (for we must not make a man our friend against his will; we
must recognize that we were mistaken at the first and took a benefit from a person we should not have taken
it from-since it was not from a friend, nor from one who did it just for the sake of acting so-and we must
settle up just as if we had been benefited on fixed terms). Indeed, one would agree to repay if one could (if
one could not, even the giver would not have expected one to do so); therefore if it is possible we must repay.
But at the outset we must consider the man by whom we are being benefited and on what terms he is acting,
in order that we may accept the benefit on these terms, or else decline it.

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It is disputable whether we ought to measure a service by its utility to the receiver and make the return with a
view to that, or by the benevolence of the giver. For those who have received say they have received from
their benefactors what meant little to the latter and what they might have got from others-minimizing the
service; while the givers, on the contrary, say it was the biggest thing they had, and what could not have been
got from others, and that it was given in times of danger or similar need. Now if the friendship is one that
aims at utility, surely the advantage to the receiver is the measure. For it is he that asks for the service, and
the other man helps him on the assumption that he will receive the equivalent; so the assistance has been
precisely as great as the advantage to the receiver, and therefore he must return as much as he has received, or
even more (for that would be nobler). In friendships based on virtue on the other hand, complaints do not
arise, but the purpose of the doer is a sort of measure; for in purpose lies the essential element of virtue and
character.

Differences arise also in friendships based on superiority; for each expects to get more out of them, but when
this happens the friendship is dissolved. Not only does the better man think he ought to get more, since more
should be assigned to a good man, but the more useful similarly expects this; they say a useless man should
not get as much as they should, since it becomes an act of public service and not a friendship if the proceeds
of the friendship do not answer to the worth of the benefits conferred. For they think that, as in a commercial
partnership those who put more in get more out, so it should be in friendship. But the man who is in a state of
need and inferiority makes the opposite claim; they think it is the part of a good friend to help those who are
in need; what, they say, is the use of being the friend of a good man or a powerful man, if one is to get
nothing out of it?

At all events it seems that each party is justified in his claim, and that each should get more out of the
friendship than the other-not more of the same thing, however, but the superior more honour and the inferior
more gain; for honour is the prize of virtue and of beneficence, while gain is the assistance required by
inferiority.

It seems to be so in constitutional arrangements also; the man who contributes nothing good to the common
stock is not honoured; for what belongs to the public is given to the man who benefits the public, and honour
does belong to the public. It is not possible to get wealth from the common stock and at the same time
honour. For no one puts up with the smaller share in all things; therefore to the man who loses in wealth they
assign honour and to the man who is willing to be paid, wealth, since the proportion to merit equalizes the
parties and preserves the friendship, as we have said. This then is also the way in which we should associate
with unequals; the man who is benefited in respect of wealth or virtue must give honour in return, repaying
what he can. For friendship asks a man to do what he can, not what is proportional to the merits of the case;
since that cannot always be done, e.g. in honours paid to the gods or to parents; for no one could ever return
to them the equivalent of what he gets, but the man who serves them to the utmost of his power is thought to
be a good man. This is why it would not seem open to a man to disown his father (though a father may
disown his son); being in debt, he should repay, but there is nothing by doing which a son will have done the
equivalent of what he has received, so that he is always in debt. But creditors can remit a debt; and a father
can therefore do so too. At the same time it is thought that presumably no one would repudiate a son who was
not far gone in wickedness; for apart from the natural friendship of father and son it is human nature not to
reject a son's assistance. But the son, if he is wicked, will naturally avoid aiding his father, or not be zealous
about it; for most people wish to get benefits, but avoid doing them, as a thing unprofitable.-So much for
these questions.

BOOK IX

IN all friendships between dissimilars it is, as we have said, proportion that equalizes the parties and
preserves the friendship; e.g. in the political form of friendship the shoemaker gets a return for his shoes in
proportion to his worth, and the weaver and all other craftsmen do the same. Now here a common measure

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has been provided in the form of money, and therefore everything is referred to this and measured by this; but
in the friendship of lovers sometimes the lover complains that his excess of love is not met by love in return
though perhaps there is nothing lovable about him), while often the beloved complains that the lover who
formerly promised everything now performs nothing. Such incidents happen when the lover loves the
beloved for the sake of pleasure while the beloved loves the lover for the sake of utility, and they do not both
possess the qualities expected of them. If these be the objects of the friendship it is dissolved when they do
not get the things that formed the motives of their love; for each did not love the other person himself but the
qualities he had, and these were not enduring; that is why the friendships also are transient. But the love of
characters, as has been said, endures because it is self-dependent. Differences arise when what they get is
something different and not what they desire; for it is like getting nothing at all when we do not get what we
aim at; compare the story of the person who made promises to a lyre-player, promising him the more, the
better he sang, but in the morning, when the other demanded the fulfilment of his promises, said that he had
given pleasure for pleasure. Now if this had been what each wanted, all would have been well; but if the one
wanted enjoyment but the other gain, and the one has what he wants while the other has not, the terms of the
association will not have been properly fulfilled; for what each in fact wants is what he attends to, and it is for
the sake of that that that he will give what he has.

But who is to fix the worth of the service; he who makes the sacrifice or he who has got the advantage? At
any rate the other seems to leave it to him. This is what they say Protagoras used to do; whenever he taught
anything whatsoever, he bade the learner assess the value of the knowledge, and accepted the amount so
fixed. But in such matters some men approve of the saying 'let a man have his fixed reward'. Those who get
the money first and then do none of the things they said they would, owing to the extravagance of their
promises, naturally find themselves the objects of complaint; for they do not fulfil what they agreed to. The
sophists are perhaps compelled to do this because no one would give money for the things they do know.
These people then, if they do not do what they have been paid for, are naturally made the objects of
complaint.

But where there is no contract of service, those who give up something for the sake of the other party cannot
(as we have said) be complained of (for that is the nature of the friendship of virtue), and the return to them
must be made on the basis of their purpose (for it is purpose that is the characteristic thing in a friend and in
virtue). And so too, it seems, should one make a return to those with whom one has studied philosophy; for
their worth cannot be measured against money, and they can get no honour which will balance their services,
but still it is perhaps enough, as it is with the gods and with one's parents, to give them what one can.

If the gift was not of this sort, but was made with a view to a return, it is no doubt preferable that the return
made should be one that seems fair to both parties, but if this cannot be achieved, it would seem not only
necessary that the person who gets the first service should fix the reward, but also just; for if the other gets in
return the equivalent of the advantage the beneficiary has received, or the price lie would have paid for the
pleasure, he will have got what is fair as from the other.

We see this happening too with things put up for sale, and in some places there are laws providing that no
actions shall arise out of voluntary contracts, on the assumption that one should settle with a person to whom
one has given credit, in the spirit in which one bargained with him. The law holds that it is more just that the
person to whom credit was given should fix the terms than that the person who gave credit should do so. For
most things are not assessed at the same value by those who have them and those who want them; each class
values highly what is its own and what it is offering; yet the return is made on the terms fixed by the receiver.
But no doubt the receiver should assess a thing not at what it seems worth when he has it, but at what he
assessed it at before he had it.

A further problem is set by such questions as, whether one should in all things give the preference to one's
father and obey him, or whether when one is ill one should trust a doctor, and when one has to elect a general

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should elect a man of military skill; and similarly whether one should render a service by preference to a
friend or to a good man, and should show gratitude to a benefactor or oblige a friend, if one cannot do both.

All such questions are hard, are they not, to decide with precision? For they admit of many variations of all
sorts in respect both of the magnitude of the service and of its nobility necessity. But that we should not give
the preference in all things to the same person is plain enough; and we must for the most part return benefits
rather than oblige friends, as we must pay back a loan to a creditor rather than make one to a friend. But
perhaps even this is not always true; e.g. should a man who has been ransomed out of the hands of brigands
ransom his ransomer in return, whoever he may be (or pay him if he has not been captured but demands
payment) or should he ransom his father? It would seem that he should ransom his father in preference even
to himself. As we have said, then, generally the debt should be paid, but if the gift is exceedingly noble or
exceedingly necessary, one should defer to these considerations. For sometimes it is not even fair to return
the equivalent of what one has received, when the one man has done a service to one whom he knows to be
good, while the other makes a return to one whom he believes to be bad. For that matter, one should
sometimes not lend in return to one who has lent to oneself; for the one person lent to a good man, expecting
to recover his loan, while the other has no hope of recovering from one who is believed to be bad. Therefore
if the facts really are so, the demand is not fair; and if they are not, but people think they are, they would be
held to be doing nothing strange in refusing. As we have often pointed out, then, discussions about feelings
and actions have just as much definiteness as their subject-matter.

That we should not make the same return to every one, nor give a father the preference in everything, as one
does not sacrifice everything to Zeus, is plain enough; but since we ought to render different things to
parents, brothers, comrades, and benefactors, we ought to render to each class what is appropriate and
becoming. And this is what people seem in fact to do; to marriages they invite their kinsfolk; for these have a
part in the family and therefore in the doings that affect the family; and at funerals also they think that
kinsfolk, before all others, should meet, for the same reason. And it would be thought that in the matter of
food we should help our parents before all others, since we owe our own nourishment to them, and it is more
honourable to help in this respect the authors of our being even before ourselves; and honour too one should
give to one's parents as one does to the gods, but not any and every honour; for that matter one should not
give the same honour to one's father and one's mother, nor again should one give them the honour due to a
philosopher or to a general, but the honour due to a father, or again to a mother. To all older persons, too, one
should give honour appropriate to their age, by rising to receive them and finding seats for them and so on;
while to comrades and brothers one should allow freedom of speech and common use of all things. To
kinsmen, too, and fellow-tribesmen and fellow-citizens and to every other class one should always try to
assign what is appropriate, and to compare the claims of each class with respect to nearness of relation and to
virtue or usefulness. The comparison is easier when the persons belong to the same class, and more laborious
when they are different. Yet we must not on that account shrink from the task, but decide the question as best
we can.

Another question that arises is whether friendships should or should not be broken off when the other party
does not remain the same. Perhaps we may say that there is nothing strange in breaking off a friendship based
on utility or pleasure, when our friends no longer have these attributes. For it was of these attributes that we
were the friends; and when these have failed it is reasonable to love no longer. But one might complain of
another if, when he loved us for our usefulness or pleasantness, he pretended to love us for our character. For,
as we said at the outset, most differences arise between friends when they are not friends in the spirit in which
they think they are. So when a man has deceived himself and has thought he was being loved for his
character, when the other person was doing nothing of the kind, he must blame himself; when he has been
deceived by the pretences of the other person, it is just that he should complain against his deceiver; he will
complain with more justice than one does against people who counterfeit the currency, inasmuch as the
wrongdoing is concerned with something more valuable.

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But if one accepts another man as good, and he turns out badly and is seen to do so, must one still love him?
Surely it is impossible, since not everything can be loved, but only what is good. What is evil neither can nor
should be loved; for it is not one's duty to be a lover of evil, nor to become like what is bad; and we have said
that like is dear like. Must the friendship, then, be forthwith broken off? Or is this not so in all cases, but only
when one's friends are incurable in their wickedness? If they are capable of being reformed one should rather
come to the assistance of their character or their property, inasmuch as this is better and more characteristic of
friendship. But a man who breaks off such a friendship would seem to be doing nothing strange; for it was
not to a man of this sort that he was a friend; when his friend has changed, therefore, and he is unable to save
him, he gives him up.

But if one friend remained the same while the other became better and far outstripped him in virtue, should
the latter treat the former as a friend? Surely he cannot. When the interval is great this becomes most plain,
e.g. in the case of childish friendships; if one friend remained a child in intellect while the other became a
fully developed man, how could they be friends when they neither approved of the same things nor delighted
in and were pained by the same things? For not even with regard to each other will their tastes agree, and
without this (as we saw) they cannot be friends; for they cannot live together. But we have discussed these
matters.

Should he, then, behave no otherwise towards him than he would if he had never been his friend? Surely he
should keep a remembrance of their former intimacy, and as we think we ought to oblige friends rather than
strangers, so to those who have been our friends we ought to make some allowance for our former friendship,
when the breach has not been due to excess of wickedness.

Friendly relations with one's neighbours, and the marks by which friendships are defined, seem to have
proceeded from a man's relations to himself. For (1) we define a friend as one who wishes and does what is
good, or seems so, for the sake of his friend, or (2) as one who wishes his friend to exist and live, for his sake;
which mothers do to their children, and friends do who have come into conflict. And (3) others define him as
one who lives with and (4) has the same tastes as another, or (5) one who grieves and rejoices with his friend;
and this too is found in mothers most of all. It is by some one of these characterstics that friendship too is
defined.

Now each of these is true of the good man's relation to himself (and of all other men in so far as they think
themselves good; virtue and the good man seem, as has been said, to be the measure of every class of things).
For his opinions are harmonious, and he desires the same things with all his soul; and therefore he wishes for
himself what is good and what seems so, and does it (for it is characteristic of the good man to work out the
good), and does so for his own sake (for he does it for the sake of the intellectual element in him, which is
thought to be the man himself); and he wishes himself to live and be preserved, and especially the element by
virtue of which he thinks. For existence is good to the virtuous man, and each man wishes himself what is
good, while no one chooses to possess the whole world if he has first to become some one else (for that
matter, even now God possesses the good); he wishes for this only on condition of being whatever he is; and
the element that thinks would seem to be the individual man, or to be so more than any other element in him.
And such a man wishes to live with himself; for he does so with pleasure, since the memories of his past acts
are delightful and his hopes for the future are good, and therefore pleasant. His mind is well stored too with
subjects of contemplation. And he grieves and rejoices, more than any other, with himself; for the same thing
is always painful, and the same thing always pleasant, and not one thing at one time and another at another;
he has, so to speak, nothing to repent of.

Therefore, since each of these characteristics belongs to the good man in relation to himself, and he is related
to his friend as to himself (for his friend is another self), friendship too is thought to be one of these
attributes, and those who have these attributes to be friends. Whether there is or is not friendship between a
man and himself is a question we may dismiss for the present; there would seem to be friendship in so far as

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he is two or more, to judge from the afore-mentioned attributes of friendship, and from the fact that the
extreme of friendship is likened to one's love for oneself.

But the attributes named seem to belong even to the majority of men, poor creatures though they may be. Are
we to say then that in so far as they are satisfied with themselves and think they are good, they share in these
attributes? Certainly no one who is thoroughly bad and impious has these attributes, or even seems to do so.
They hardly belong even to inferior people; for they are at variance with themselves, and have appetites for
some things and rational desires for others. This is true, for instance, of incontinent people; for they choose,
instead of the things they themselves think good, things that are pleasant but hurtful; while others again,
through cowardice and laziness, shrink from doing what they think best for themselves. And those who have
done many terrible deeds and are hated for their wickedness even shrink from life and destroy themselves.
And wicked men seek for people with whom to spend their days, and shun themselves; for they remember
many a grevious deed, and anticipate others like them, when they are by themselves, but when they are with
others they forget. And having nothing lovable in them they have no feeling of love to themselves. Therefore
also such men do not rejoice or grieve with themselves; for their soul is rent by faction, and one element in it
by reason of its wickedness grieves when it abstains from certain acts, while the other part is pleased, and one
draws them this way and the other that, as if they were pulling them in pieces. If a man cannot at the same
time be pained and pleased, at all events after a short time he is pained because he was pleased, and he could
have wished that these things had not been pleasant to him; for bad men are laden with repentance.

Therefore the bad man does not seem to be amicably disposed even to himself, because there is nothing in
him to love; so that if to be thus is the height of wretchedness, we should strain every nerve to avoid
wickedness and should endeavour to be good; for so and only so can one be either friendly to oneself or a
friend to another.

Goodwill is a friendly sort of relation, but is not identical with friendship; for one may have goodwill both
towards people whom one does not know, and without their knowing it, but not friendship. This has indeed
been said already.' But goodwill is not even friendly feeling. For it does not involve intensity or desire,
whereas these accompany friendly feeling; and friendly feeling implies intimacy while goodwill may arise of
a sudden, as it does towards competitors in a contest; we come to feel goodwill for them and to share in their
wishes, but we would not do anything with them; for, as we said, we feel goodwill suddenly and love them
only superficially.

Goodwill seems, then, to be a beginning of friendship, as the pleasure of the eye is the beginning of love. For
no one loves if he has not first been delighted by the form of the beloved, but he who delights in the form of
another does not, for all that, love him, but only does so when he also longs for him when absent and craves
for his presence; so too it is not possible for people to be friends if they have not come to feel goodwill for
each other, but those who feel goodwill are not for all that friends; for they only wish well to those for whom
they feel goodwill, and would not do anything with them nor take trouble for them. And so one might by an
extension of the term friendship say that goodwill is inactive friendship, though when it is prolonged and
reaches the point of intimacy it becomes friendship-not the friendship based on utility nor that based on
pleasure; for goodwill too does not arise on those terms. The man who has received a benefit bestows
goodwill in return for what has been done to him, but in doing so is only doing what is just; while he who
wishes some one to prosper because he hopes for enrichment through him seems to have goodwill not to him
but rather to himself, just as a man is not a friend to another if he cherishes him for the sake of some use to be
made of him. In general, goodwill arises on account of some excellence and worth, when one man seems to
another beautiful or brave or something of the sort, as we pointed out in the case of competitors in a contest.

Unanimity also seems to be a friendly relation. For this reason it is not identity of opinion; for that might
occur even with people who do not know each other; nor do we say that people who have the same views on
any and every subject are unanimous, e.g. those who agree about the heavenly bodies (for unanimity about

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these is not a friendly relation), but we do say that a city is unanimous when men have the same opinion
about what is to their interest, and choose the same actions, and do what they have resolved in common. It is
about things to be done, therefore, that people are said to be unanimous, and, among these, about matters of
consequence and in which it is possible for both or all parties to get what they want; e.g. a city is unanimous
when all its citizens think that the offices in it should be elective, or that they should form an alliance with
Sparta, or that Pittacus should be their ruler-at a time when he himself was also willing to rule. But when
each of two people wishes himself to have the thing in question, like the captains in the Phoenissae, they are
in a state of faction; for it is not unanimity when each of two parties thinks of the same thing, whatever that
may be, but only when they think of the same thing in the same hands, e.g. when both the common people
and those of the better class wish the best men to rule; for thus and thus alone do all get what they aim at.
Unanimity seems, then, to be political friendship, as indeed it is commonly said to be; for it is concerned with
things that are to our interest and have an influence on our life.

Now such unanimity is found among good men; for they are unanimous both in themselves and with one
another, being, so to say, of one mind (for the wishes of such men are constant and not at the mercy of
opposing currents like a strait of the sea), and they wish for what is just and what is advantageous, and these
are the objects of their common endeavour as well. But bad men cannot be unanimous except to a small
extent, any more than they can be friends, since they aim at getting more than their share of advantages, while
in labour and public service they fall short of their share; and each man wishing for advantage to himself
criticizes his neighbour and stands in his way; for if people do not watch it carefully the common weal is
soon destroyed. The result is that they are in a state of faction, putting compulsion on each other but
unwilling themselves to do what is just.

Benefactors are thought to love those they have benefited, more than those who have been well treated love
those that have treated them well, and this is discussed as though it were paradoxical. Most people think it is
because the latter are in the position of debtors and the former of creditors; and therefore as, in the case of
loans, debtors wish their creditors did not exist, while creditors actually take care of the safety of their
debtors, so it is thought that benefactors wish the objects of their action to exist since they will then get their
gratitude, while the beneficiaries take no interest in making this return. Epicharmus would perhaps declare
that they say this because they 'look at things on their bad side', but it is quite like human nature; for most
people are forgetful, and are more anxious to be well treated than to treat others well. But the cause would
seem to be more deeply rooted in the nature of things; the case of those who have lent money is not even
analogous. For they have no friendly feeling to their debtors, but only a wish that they may kept safe with a
view to what is to be got from them; while those who have done a service to others feel friendship and love
for those they have served even if these are not of any use to them and never will be. This is what happens
with craftsmen too; every man loves his own handiwork better than he would be loved by it if it came alive;
and this happens perhaps most of all with poets; for they have an excessive love for their own poems, doting
on them as if they were their children. This is what the position of benefactors is like; for that which they
have treated well is their handiwork, and therefore they love this more than the handiwork does its maker.
The cause of this is that existence is to all men a thing to be chosen and loved, and that we exist by virtue of
activity (i.e. by living and acting), and that the handiwork is in a sense, the producer in activity; he loves his
handiwork, therefore, because he loves existence. And this is rooted in the nature of things; for what he is in
potentiality, his handiwork manifests in activity.

At the same time to the benefactor that is noble which depends on his action, so that he delights in the object
of his action, whereas to the patient there is nothing noble in the agent, but at most something advantageous,
and this is less pleasant and lovable. What is pleasant is the activity of the present, the hope of the future, the
memory of the past; but most pleasant is that which depends on activity, and similarly this is most lovable.
Now for a man who has made something his work remains (for the noble is lasting), but for the person acted
on the utility passes away. And the memory of noble things is pleasant, but that of useful things is not likely
to be pleasant, or is less so; though the reverse seems true of expectation.

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Further, love is like activity, being loved like passivity; and loving and its concomitants are attributes of those
who are the more active.

Again, all men love more what they have won by labour; e.g. those who have made their money love it more
than those who have inherited it; and to be well treated seems to involve no labour, while to treat others well
is a laborious task. These are the reasons, too, why mothers are fonder of their children than fathers; bringing
them into the world costs them more pains, and they know better that the children are their own. This last
point, too, would seem to apply to benefactors.

The question is also debated, whether a man should love himself most, or some one else. People criticize
those who love themselves most, and call them self-lovers, using this as an epithet of disgrace, and a bad
man seems to do everything for his own sake, and the more so the more wicked he is-and so men reproach
him, for instance, with doing nothing of his own accord-while the good man acts for honour's sake, and the
more so the better he is, and acts for his friend's sake, and sacrifices his own interest.

But the facts clash with these arguments, and this is not surprising. For men say that one ought to love best
one's best friend, and man's best friend is one who wishes well to the object of his wish for his sake, even if
no one is to know of it; and these attributes are found most of all in a man's attitude towards himself, and so
are all the other attributes by which a friend is defined; for, as we have said, it is from this relation that all the
characteristics of friendship have extended to our neighbours. All the proverbs, too, agree with this, e.g. 'a
single soul', and 'what friends have is common property', and 'friendship is equality', and 'charity begins at
home'; for all these marks will be found most in a man's relation to himself; he is his own best friend and
therefore ought to love himself best. It is therefore a reasonable question, which of the two views we should
follow; for both are plausible.

Perhaps we ought to mark off such arguments from each other and determine how far and in what respects
each view is right. Now if we grasp the sense in which each school uses the phrase 'lover of self, the truth
may become evident. Those who use the term as one of reproach ascribe self-love to people who assign to
themselves the greater share of wealth, honours, and bodily pleasures; for these are what most people desire,
and busy themselves about as though they were the best of all things, which is the reason, too, why they
become objects of competition. So those who are grasping with regard to these things gratify their appetites
and in general their feelings and the irrational element of the soul; and most men are of this nature (which is
the reason why the epithet has come to be used as it is-it takes its meaning from the prevailing type of
self-love, which is a bad one); it is just, therefore, that men who are lovers of self in this way are reproached
for being so. That it is those who give themselves the preference in regard to objects of this sort that most
people usually call lovers of self is plain; for if a man were always anxious that he himself, above all things,
should act justly, temperately, or in accordance with any other of the virtues, and in general were always to
try to secure for himself the honourable course, no one will call such a man a lover of self or blame him.

But such a man would seem more than the other a lover of self; at all events he assigns to himself the things
that are noblest and best, and gratifies the most authoritative element in and in all things obeys this; and just
as a city or any other systematic whole is most properly identified with the most authoritative element in it, so
is a man; and therefore the man who loves this and gratifies it is most of all a lover of self. Besides, a man is
said to have or not to have self-control according as his reason has or has not the control, on the assumption
that this is the man himself; and the things men have done on a rational principle are thought most properly
their own acts and voluntary acts. That this is the man himself, then, or is so more than anything else, is plain,
and also that the good man loves most this part of him. Whence it follows that he is most truly a lover of self,
of another type than that which is a matter of reproach, and as different from that as living according to a
rational principle is from living as passion dictates, and desiring what is noble from desiring what seems
advantageous. Those, then, who busy themselves in an exceptional degree with noble actions all men approve
and praise; and if all were to strive towards what is noble and strain every nerve to do the noblest deeds,

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everything would be as it should be for the common weal, and every one would secure for himself the goods
that are greatest, since virtue is the greatest of goods.

Therefore the good man should be a lover of self (for he will both himself profit by doing noble acts, and will
benefit his fellows), but the wicked man should not; for he will hurt both himself and his neighbours,
following as he does evil passions. For the wicked man, what he does clashes with what he ought to do, but
what the good man ought to do he does; for reason in each of its possessors chooses what is best for itself,
and the good man obeys his reason. It is true of the good man too that he does many acts for the sake of his
friends and his country, and if necessary dies for them; for he will throw away both wealth and honours and
in general the goods that are objects of competition, gaining for himself nobility; since he would prefer a
short period of intense pleasure to a long one of mild enjoyment, a twelvemonth of noble life to many years
of humdrum existence, and one great and noble action to many trivial ones. Now those who die for others
doubtless attain this result; it is therefore a great prize that they choose for themselves. They will throw away
wealth too on condition that their friends will gain more; for while a man's friend gains wealth he himself
achieves nobility; he is therefore assigning the greater good to himself. The same too is true of honour and
office; all these things he will sacrifice to his friend; for this is noble and laudable for himself. Rightly then is
he thought to be good, since he chooses nobility before all else. But he may even give up actions to his
friend; it may be nobler to become the cause of his friend's acting than to act himself. In all the actions,
therefore, that men are praised for, the good man is seen to assign to himself the greater share in what is
noble. In this sense, then, as has been said, a man should be a lover of self; but in the sense in which most
men are so, he ought not.

It is also disputed whether the happy man will need friends or not. It is said that those who are supremely
happy and self-sufficient have no need of friends; for they have the things that are good, and therefore being
self-sufficient they need nothing further, while a friend, being another self, furnishes what a man cannot
provide by his own effort; whence the saying 'when fortune is kind, what need of friends?' But it seems
strange, when one assigns all good things to the happy man, not to assign friends, who are thought the
greatest of external goods. And if it is more characteristic of a friend to do well by another than to be well
done by, and to confer benefits is characteristic of the good man and of virtue, and it is nobler to do well by
friends than by strangers, the good man will need people to do well by. This is why the question is asked
whether we need friends more in prosperity or in adversity, on the assumption that not only does a man in
adversity need people to confer benefits on him, but also those who are prospering need people to do well by.
Surely it is strange, too, to make the supremely happy man a solitary; for no one would choose the whole
world on condition of being alone, since man is a political creature and one whose nature is to live with
others. Therefore even the happy man lives with others; for he has the things that are by nature good. And
plainly it is better to spend his days with friends and good men than with strangers or any chance persons.
Therefore the happy man needs friends.

What then is it that the first school means, and in what respect is it right? Is it that most identify friends with
useful people? Of such friends indeed the supremely happy man will have no need, since he already has the
things that are good; nor will he need those whom one makes one's friends because of their pleasantness, or
he will need them only to a small extent (for his life, being pleasant, has no need of adventitious pleasure);
and because he does not need such friends he is thought not to need friends.

But that is surely not true. For we have said at the outset that happiness is an activity; and activity plainly
comes into being and is not present at the start like a piece of property. If (1) happiness lies in living and
being active, and the good man's activity is virtuous and pleasant in itself, as we have said at the outset, and
(2) a thing's being one's own is one of the attributes that make it pleasant, and (3) we can contemplate our
neighbours better than ourselves and their actions better than our own, and if the actions of virtuous men who
are their friends are pleasant to good men (since these have both the attributes that are naturally pleasant),-if
this be so, the supremely happy man will need friends of this sort, since his purpose is to contemplate worthy

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actions and actions that are his own, and the actions of a good man who is his friend have both these qualities.

Further, men think that the happy man ought to live pleasantly. Now if he were a solitary, life would be hard
for him; for by oneself it is not easy to be continuously active; but with others and towards others it is easier.
With others therefore his activity will be more continuous, and it is in itself pleasant, as it ought to be for the
man who is supremely happy; for a good man qua good delights in virtuous actions and is vexed at vicious
ones, as a musical man enjoys beautiful tunes but is pained at bad ones. A certain training in virtue arises also
from the company of the good, as Theognis has said before us.

If we look deeper into the nature of things, a virtuous friend seems to be naturally desirable for a virtuous
man. For that which is good by nature, we have said, is for the virtuous man good and pleasant in itself. Now
life is defined in the case of animals by the power of perception in that of man by the power of perception or
thought; and a power is defined by reference to the corresponding activity, which is the essential thing;
therefore life seems to be essentially the act of perceiving or thinking. And life is among the things that are
good and pleasant in themselves, since it is determinate and the determinate is of the nature of the good; and
that which is good by nature is also good for the virtuous man (which is the reason why life seems pleasant to
all men); but we must not apply this to a wicked and corrupt life nor to a life spent in pain; for such a life is
indeterminate, as are its attributes. The nature of pain will become plainer in what follows. But if life itself is
good and pleasant (which it seems to be, from the very fact that all men desire it, and particularly those who
are good and supremely happy; for to such men life is most desirable, and their existence is the most
supremely happy) and if he who sees perceives that he sees, and he who hears, that he hears, and he who
walks, that he walks, and in the case of all other activities similarly there is something which perceives that
we are active, so that if we perceive, we perceive that we perceive, and if we think, that we think; and if to
perceive that we perceive or think is to perceive that we exist (for existence was defined as perceiving or
thinking); and if perceiving that one lives is in itself one of the things that are pleasant (for life is by nature
good, and to perceive what is good present in oneself is pleasant); and if life is desirable, and particularly so
for good men, because to them existence is good and pleasant for they are pleased at the consciousness of the
presence in them of what is in itself good); and if as the virtuous man is to himself, he is to his friend also (for
his friend is another self):-if all this be true, as his own being is desirable for each man, so, or almost so, is
that of his friend. Now his being was seen to be desirable because he perceived his own goodness, and such
perception is pleasant in itself. He needs, therefore, to be conscious of the existence of his friend as well, and
this will be realized in their living together and sharing in discussion and thought; for this is what living
together would seem to mean in the case of man, and not, as in the case of cattle, feeding in the same place.

If, then, being is in itself desirable for the supremely happy man (since it is by its nature good and pleasant),
and that of his friend is very much the same, a friend will be one of the things that are desirable. Now that
which is desirable for him he must have, or he will be deficient in this respect. The man who is to be happy
will therefore need virtuous friends.

Should we, then, make as many friends as possible, or-as in the case of hospitality it is thought to be suitable
advice, that one should be 'neither a man of many guests nor a man with none'-will that apply to friendship as
well; should a man neither be friendless nor have an excessive number of friends?

To friends made with a view to utility this saying would seem thoroughly applicable; for to do services to
many people in return is a laborious task and life is not long enough for its performance. Therefore friends in
excess of those who are sufficient for our own life are superfluous, and hindrances to the noble life; so that
we have no need of them. Of friends made with a view to pleasure, also, few are enough, as a little seasoning
in food is enough.

But as regards good friends, should we have as many as possible, or is there a limit to the number of one's
friends, as there is to the size of a city? You cannot make a city of ten men, and if there are a hundred

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thousand it is a city no longer. But the proper number is presumably not a single number, but anything that
falls between certain fixed points. So for friends too there is a fixed number perhaps the largest number with
whom one can live together (for that, we found, thought to be very characteristic of friendship); and that one
cannot live with many people and divide oneself up among them is plain. Further, they too must be friends of
one another, if they are all to spend their days together; and it is a hard business for this condition to be
fulfilled with a large number. It is found difficult, too, to rejoice and to grieve in an intimate way with many
people, for it may likely happen that one has at once to be happy with one friend and to mourn with another.
Presumably, then, it is well not to seek to have as many friends as possible, but as many as are enough for the
purpose of living together; for it would seem actually impossible to be a great friend to many people. This is
why one cannot love several people; love is ideally a sort of excess of friendship, and that can only be felt
towards one person; therefore great friendship too can only be felt towards a few people. This seems to be
confirmed in practice; for we do not find many people who are friends in the comradely way of friendship,
and the famous friendships of this sort are always between two people. Those who have many friends and
mix intimately with them all are thought to be no one's friend, except in the way proper to fellow-citizens,
and such people are also called obsequious. In the way proper to fellow-citizens, indeed, it is possible to be
the friend of many and yet not be obsequious but a genuinely good man; but one cannot have with many
people the friendship based on virtue and on the character of our friends themselves, and we must be content
if we find even a few such.

Do we need friends more in good fortune or in bad? They are sought after in both; for while men in adversity
need help, in prosperity they need people to live with and to make the objects of their beneficence; for they
wish to do well by others. Friendship, then, is more necessary in bad fortune, and so it is useful friends that
one wants in this case; but it is more noble in good fortune, and so we also seek for good men as our friends,
since it is more desirable to confer benefits on these and to live with these. For the very presence of friends is
pleasant both in good fortune and also in bad, since grief is lightened when friends sorrow with us. Hence one
might ask whether they share as it were our burden, or-without that happening-their presence by its
pleasantness, and the thought of their grieving with us, make our pain less. Whether it is for these reasons or
for some other that our grief is lightened, is a question that may be dismissed; at all events what we have
described appears to take place.

But their presence seems to contain a mixture of various factors. The very seeing of one's friends is pleasant,
especially if one is in adversity, and becomes a safeguard against grief (for a friend tends to comfort us both
by the sight of him and by his words, if he is tactful, since he knows our character and the things that please
or pain us); but to see him pained at our misfortunes is painful; for every one shuns being a cause of pain to
his friends. For this reason people of a manly nature guard against making their friends grieve with them, and,
unless he be exceptionally insensible to pain, such a man cannot stand the pain that ensues for his friends, and
in general does not admit fellow-mourners because he is not himself given to mourning; but women and
womanly men enjoy sympathisers in their grief, and love them as friends and companions in sorrow. But in
all things one obviously ought to imitate the better type of person.

On the other hand, the presence of friends in our prosperity implies both a pleasant passing of our time and
the pleasant thought of their pleasure at our own good fortune. For this cause it would seem that we ought to
summon our friends readily to share our good fortunes (for the beneficent character is a noble one), but
summon them to our bad fortunes with hesitation; for we ought to give them as little a share as possible in
our evils whence the saying 'enough is my misfortune'. We should summon friends to us most of all when
they are likely by suffering a few inconveniences to do us a great service.

Conversely, it is fitting to go unasked and readily to the aid of those in adversity (for it is characteristic of a
friend to render services, and especially to those who are in need and have not demanded them; such action is
nobler and pleasanter for both persons); but when our friends are prosperous we should join readily in their
activities (for they need friends for these too), but be tardy in coming forward to be the objects of their

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kindness; for it is not noble to be keen to receive benefits. Still, we must no doubt avoid getting the reputation
of kill-joys by repulsing them; for that sometimes happens.

The presence of friends, then, seems desirable in all circumstances.

Does it not follow, then, that, as for lovers the sight of the beloved is the thing they love most, and they prefer
this sense to the others because on it love depends most for its being and for its origin, so for friends the most
desirable thing is living together? For friendship is a partnership, and as a man is to himself, so is he to his
friend; now in his own case the consciousness of his being is desirable, and so therefore is the consciousness
of his friend's being, and the activity of this consciousness is produced when they live together, so that it is
natural that they aim at this. And whatever existence means for each class of men, whatever it is for whose
sake they value life, in that they wish to occupy themselves with their friends; and so some drink together,
others dice together, others join in athletic exercises and hunting, or in the study of philosophy, each class
spending their days together in whatever they love most in life; for since they wish to live with their friends,
they do and share in those things which give them the sense of living together. Thus the friendship of bad
men turns out an evil thing (for because of their instability they unite in bad pursuits, and besides they
become evil by becoming like each other), while the friendship of good men is good, being augmented by
their companionship; and they are thought to become better too by their activities and by improving each
other; for from each other they take the mould of the characteristics they approve-whence the saying 'noble
deeds from noble men'. -So much, then, for friendship; our next task must be to discuss pleasure.

BOOKX

AFTER these matters we ought perhaps next to discuss pleasure. For it is thought to be most intimately
connected with our human nature, which is the reason why in educating the young we steer them by the
rudders of pleasure and pain; it is thought, too, that to enjoy the things we ought and to hate the things we
ought has the greatest bearing on virtue of character. For these things extend right through life, with a weight
and power of their own in respect both to virtue and to the happy life, since men choose what is pleasant and
avoid what is painful; and such things, it will be thought, we should least of all omit to discuss, especially
since they admit of much dispute. For some say pleasure is the good, while others, on the contrary, say it is
thoroughly bad-some no doubt being persuaded that the facts are so, and others thinking it has a better effect
on our life to exhibit pleasure as a bad thing even if it is not; for most people (they think) incline towards it
and are the slaves of their pleasures, for which reason they ought to lead them in the opposite direction, since
thus they will reach the middle state. But surely this is not correct. For arguments about matters concerned
with feelings and actions are less reliable than facts: and so when they clash with the facts of perception they
are despised, and discredit the truth as well; if a man who runs down pleasure is once seen to be aiming at it,
his inclining towards it is thought to imply that it is all worthy of being aimed at; for most people are not
good at drawing distinctions. True arguments seem, then, most useful, not only with a view to knowledge, but
with a view to life also; for since they harmonize with the facts they are believed, and so they stimulate those
who understand them to live according to them.-Enough of such questions; let us proceed to review the
opinions that have been expressed about pleasure.

Eudoxus thought pleasure was the good because he saw all things, both rational and irrational, aiming at it,
and because in all things that which is the object of choice is what is excellent, and that which is most the
object of choice the greatest good; thus the fact that all things moved towards the same object indicated that
this was for all things the chief good (for each thing, he argued, finds its own good, as it finds its own
nourishment); and that which is good for all things and at which all aim was the good. His arguments were
credited more because of the excellence of his character than for their own sake; he was thought to be
remarkably self-controlled, and therefore it was thought that he was not saying what he did say as a friend of
pleasure, but that the facts really were so. He believed that the same conclusion followed no less plainly from
a study of the contrary of pleasure; pain was in itself an object of aversion to all things, and therefore its

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contrary must be similarly an object of choice. And again that is most an object of choice which we choose
not because or for the sake of something else, and pleasure is admittedly of this nature; for no one asks to
what end he is pleased, thus implying that pleasure is in itself an object of choice. Further, he argued that
pleasure when added to any good, e.g. to just or temperate action, makes it more worthy of choice, and that it
is only by itself that the good can be increased.

This argument seems to show it to be one of the goods, and no more a good than any other; for every good is
more worthy of choice along with another good than taken alone. And so it is by an argument of this kind that
Plato proves the good not to be pleasure; he argues that the pleasant life is more desirable with wisdom than
without, and that if the mixture is better, pleasure is not the good; for the good cannot become more desirable
by the addition of anything to it. Now it is clear that nothing else, any more than pleasure, can be the good if
it is made more desirable by the addition of any of the things that are good in themselves. What, then, is there
that satisfies this criterion, which at the same time we can participate in? It is something of this sort that we
are looking for. Those who object that that at which all things aim is not necessarily good are, we may
surmise, talking nonsense. For we say that that which every one thinks really is so; and the man who attacks
this belief will hardly have anything more credible to maintain instead. If it is senseless creatures that desire
the things in question, there might be something in what they say; but if intelligent creatures do so as well,
what sense can there be in this view? But perhaps even in inferior creatures there is some natural good
stronger than themselves which aims at their proper good.

Nor does the argument about the contrary of pleasure seem to be correct. They say that if pain is an evil it
does not follow that pleasure is a good; for evil is opposed to evil and at the same time both are opposed to
the neutral state-which is correct enough but does not apply to the things in question. For if both pleasure and
pain belonged to the class of evils they ought both to be objects of aversion, while if they belonged to the
class of neutrals neither should be an object of aversion or they should both be equally so; but in fact people
evidently avoid the one as evil and choose the other as good; that then must be the nature of the opposition
between them.

Nor again, if pleasure is not a quality, does it follow that it is not a good; for the activities of virtue are not
qualities either, nor is happiness. They say, however, that the good is determinate, while pleasure is
indeterminate, because it admits of degrees. Now if it is from the feeling of pleasure that they judge thus, the
same will be true of justice and the other virtues, in respect of which we plainly say that people of a certain
character are so more or less, and act more or less in accordance with these virtues; for people may be more
just or brave, and it is possible also to act justly or temperately more or less. But if their judgement is based
on the various pleasures, surely they are not stating the real cause, if in fact some pleasures are unmixed and
others mixed. Again, just as health admits of degrees without being indeterminate, why should not pleasure?
The same proportion is not found in all things, nor a single proportion always in the same thing, but it may be
relaxed and yet persist up to a point, and it may differ in degree. The case of pleasure also may therefore be
of this kind.

Again, they assume that the good is perfect while movements and comings into being are imperfect, and try
to exhibit pleasure as being a movement and a coming into being. But they do not seem to be right even in
saying that it is a movement. For speed and slowness are thought to be proper to every movement, and if a
movement, e.g. that of the heavens, has not speed or slowness in itself, it has it in relation to something else;
but of pleasure neither of these things is true. For while we may become pleased quickly as we may become
angry quickly, we cannot be pleased quickly, not even in relation to some one else, while we can walk, or
grow, or the like, quickly. While, then, we can change quickly or slowly into a state of pleasure, we cannot
quickly exhibit the activity of pleasure, i.e. be pleased. Again, how can it be a coming into being? It is not
thought that any chance thing can come out of any chance thing, but that a thing is dissolved into that out of
which it comes into being; and pain would be the destruction of that of which pleasure is the coming into
being.

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They say, too, that pain is the lack of that which is according to nature, and pleasure is replenishment. But
these experiences are bodily. If then pleasure is replenishment with that which is according to nature, that
which feels pleasure will be that in which the replenishment takes place, i.e. the body; but that is not thought
to be the case; therefore the replenishment is not pleasure, though one would be pleased when replenishment
was taking place, just as one would be pained if one was being operated on. This opinion seems to be based
on the pains and pleasures connected with nutrition; on the fact that when people have been short of food and
have felt pain beforehand they are pleased by the replenishment. But this does not happen with all pleasures;
for the pleasures of learning and, among the sensuous pleasures, those of smell, and also many sounds and
sights, and memories and hopes, do not presuppose pain. Of what then will these be the coming into being?
There has not been lack of anything of which they could be the supplying anew.

In reply to those who bring forward the disgraceful pleasures one may say that these are not pleasant; if
things are pleasant to people of vicious constitution, we must not suppose that they are also pleasant to others
than these, just as we do not reason so about the things that are wholesome or sweet or bitter to sick people,
or ascribe whiteness to the things that seem white to those suffering from a disease of the eye. Or one might
answer thus-that the pleasures are desirable, but not from these sources, as wealth is desirable, but not as the
reward of betrayal, and health, but not at the cost of eating anything and everything. Or perhaps pleasures
differ in kind; for those derived from noble sources are different from those derived from base sources, and
one cannot the pleasure of the just man without being just, nor that of the musical man without being musical,
and so on.

The fact, too, that a friend is different from a flatterer seems to make it plain that pleasure is not a good or
that pleasures are different in kind; for the one is thought to consort with us with a view to the good, the other
with a view to our pleasure, and the one is reproached for his conduct while the other is praised on the ground
that he consorts with us for different ends. And no one would choose to live with the intellect of a child
throughout his life, however much he were to be pleased at the things that children are pleased at, nor to get
enjoyment by doing some most disgraceful deed, though he were never to feel any pain in consequence. And
there are many things we should be keen about even if they brought no pleasure, e.g. seeing, remembering,
knowing, possessing the virtues. If pleasures necessarily do accompany these, that makes no odds; we should
choose these even if no pleasure resulted. It seems to be clear, then, that neither is pleasure the good nor is all
pleasure desirable, and that some pleasures are desirable in themselves, differing in kind or in their sources
from the others. So much for the things that are said about pleasure and pain.

What pleasure is, or what kind of thing it is, will become plainer if we take up the question aga from the
beginning. Seeing seems to be at any moment complete, for it does not lack anything which coming into
being later will complete its form; and pleasure also seems to be of this nature. For it is a whole, and at no
time can one find a pleasure whose form will be completed if the pleasure lasts longer. For this reason, too, it
is not a movement. For every movement (e.g. that of building) takes time and is for the sake of an end, and is
complete when it has made what it aims at. It is complete, therefore, only in the whole time or at that final
moment. In their parts and during the time they occupy, all movements are incomplete, and are different in
kind from the whole movement and from each other. For the fitting together of the stones is different from
the fluting of the column, and these are both different from the making of the temple; and the making of the
temple is complete (for it lacks nothing with a view to the end proposed), but the making of the base or of the
triglyph is incomplete; for each is the making of only a part. They differ in kind, then, and it is not possible to
find at any and every time a movement complete in form, but if at all, only in the whole time. So, too, in the
case of walking and all other movements. For if locomotion is a movement from to there, it, too, has
differences in kind-flying, walking, leaping, and so on. And not only so, but in walking itself there are such
differences; for the whence and whither are not the same in the whole racecourse and in a part of it, nor in
one part and in another, nor is it the same thing to traverse this line and that; for one traverses not only a line
but one which is in a place, and this one is in a different place from that. We have discussed movement with
precision in another work, but it seems that it is not complete at any and every time, but that the many

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movements are incomplete and different in kind, since the whence and whither give them their form. But of
pleasure the form is complete at any and every time. Plainly, then, pleasure and movement must be different
from each other, and pleasure must be one of the things that are whole and complete. This would seem to be
the case, too, from the fact that it is not possible to move otherwise than in time, but it is possible to be
pleased; for that which takes place in a moment is a whole.

From these considerations it is clear, too, that these thinkers are not right in saying there is a movement or a
coming into being of pleasure. For these cannot be ascribed to all things, but only to those that are divisible
and not wholes; there is no coming into being of seeing nor of a point nor of a unit, nor is any of these a
movement or coming into being; therefore there is no movement or coming into being of pleasure either; for
it is a whole.

Since every sense is active in relation to its object, and a sense which is in good condition acts perfectly in
relation to the most beautiful of its objects (for perfect activity seems to be ideally of this nature; whether we
say that it is active, or the organ in which it resides, may be assumed to be immaterial), it follows that in the
case of each sense the best activity is that of the best-conditioned organ in relation to the finest of its objects.
And this activity will be the most complete and pleasant. For, while there is pleasure in respect of any sense,
and in respect of thought and contemplation no less, the most complete is pleasantest, and that of a
well-conditioned organ in relation to the worthiest of its objects is the most complete; and the pleasure
completes the activity. But the pleasure does not complete it in the same way as the combination of object
and sense, both good, just as health and the doctor are not in the same way the cause of a man's being healthy.
(That pleasure is produced in respect to each sense is plain; for we speak of sights and sounds as pleasant. It
is also plain that it arises most of all when both the sense is at its best and it is active in reference to an object
which corresponds; when both object and perceiver are of the best there will always be pleasure, since the
requisite agent and patient are both present.) Pleasure completes the activity not as the corresponding
permanent state does, by its immanence, but as an end which supervenes as the bloom of youth does on those
in the flower of their age. So long, then, as both the intelligible or sensible object and the discriminating or
contemplative faculty are as they should be, the pleasure will be involved in the activity; for when both the
passive and the active factor are unchanged and are related to each other in the same way, the same result
naturally follows.

How, then, is it that no one is continuously pleased? Is it that we grow weary? Certainly all human beings are
incapable of continuous activity. Therefore pleasure also is not continuous; for it accompanies activity. Some
things delight us when they are new, but later do so less, for the same reason; for at first the mind is in a state
of stimulation and intensely active about them, as people are with respect to their vision when they look hard
at a thing, but afterwards our activity is not of this kind, but has grown relaxed; for which reason the pleasure
also is dulled.

One might think that all men desire pleasure because they all aim at life; life is an activity, and each man is
active about those things and with those faculties that he loves most; e.g. the musician is active with his
hearing in reference to tunes, the student with his mind in reference to theoretical questions, and so on in each
case; now pleasure completes the activities, and therefore life, which they desire. It is with good reason, then,
that they aim at pleasure too, since for every one it completes life, which is desirable. But whether we choose
life for the sake of pleasure or pleasure for the sake of life is a question we may dismiss for the present. For
they seem to be bound up together and not to admit of separation, since without activity pleasure does not
arise, and every activity is completed by the attendant pleasure.

For this reason pleasures seem, too, to differ in kind. For things different in kind are, we think, completed by
different things (we see this to be true both of natural objects and of things produced by art, e.g. animals,
trees, a painting, a sculpture, a house, an implement); and, similarly, we think that activities differing in kind
are completed by things differing in kind. Now the activities of thought differ from those of the senses, and

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both differ among themselves, in kind; so, therefore, do the pleasures that complete them.

This may be seen, too, from the fact that each of the pleasures is bound up with the activity it completes. For
an activity is intensified by its proper pleasure, since each class of things is better judged of and brought to
precision by those who engage in the activity with pleasure; e.g. it is those who enjoy geometrical thinking
that become geometers and grasp the various propositions better, and, similarly, those who are fond of music
or of building, and so on, make progress in their proper function by enjoying it; so the pleasures intensify the
activities, and what intensifies a thing is proper to it, but things different in kind have properties different in
kind.

This will be even more apparent from the fact that activities are hindered by pleasures arising from other
sources. For people who are fond of playing the flute are incapable of attending to arguments if they overhear
some one playing the flute, since they enjoy flute-playing more than the activity in hand; so the pleasure
connected with fluteplaying destroys the activity concerned with argument. This happens, similarly, in all
other cases, when one is active about two things at once; the more pleasant activity drives out the other, and if
it is much more pleasant does so all the more, so that one even ceases from the other. This is why when we
enjoy anything very much we do not throw ourselves into anything else, and do one thing only when we are
not much pleased by another; e.g. in the theatre the people who eat sweets do so most when the actors are
poor. Now since activities are made precise and more enduring and better by their proper pleasure, and
injured by alien pleasures, evidently the two kinds of pleasure are far apart. For alien pleasures do pretty
much what proper pains do, since activities are destroyed by their proper pains; e.g. if a man finds writing or
doing sums unpleasant and painful, he does not write, or does not do sums, because the activity is painful. So
an activity suffers contrary effects from its proper pleasures and pains, i.e. from those that supervene on it in
virtue of its own nature. And alien pleasures have been stated to do much the same as pain; they destroy the
activity, only not to the same degree.

Now since activities differ in respect of goodness and badness, and some are worthy to be chosen, others to
be avoided, and others neutral, so, too, are the pleasures; for to each activity there is a proper pleasure. The
pleasure proper to a worthy activity is good and that proper to an unworthy activity bad; just as the appetites
for noble objects are laudable, those for base objects culpable. But the pleasures involved in activities are
more proper to them than the desires; for the latter are separated both in time and in nature, while the former
are close to the activities, and so hard to distinguish from them that it admits of dispute whether the activity is
not the same as the pleasure. (Still, pleasure does not seem to be thought or perception-that would be strange;
but because they are not found apart they appear to some people the same.) As activities are different, then,
so are the corresponding pleasures. Now sight is superior to touch in purity, and hearing and smell to taste;
the pleasures, therefore, are similarly superior, and those of thought superior to these, and within each of the
two kinds some are superior to others.

Each animal is thought to have a proper pleasure, as it has a proper function; viz. that which corresponds to
its activity. If we survey them species by species, too, this will be evident; horse, dog, and man have different
pleasures, as Heraclitus says 'asses would prefer sweepings to gold'; for food is pleasanter than gold to asses.
So the pleasures of creatures different in kind differ in kind, and it is plausible to suppose that those of a
single species do not differ. But they vary to no small extent, in the case of men at least; the same things
delight some people and pain others, and are painful and odious to some, and pleasant to and liked by others.
This happens, too, in the case of sweet things; the same things do not seem sweet to a man in a fever and a
healthy man-nor hot to a weak man and one in good condition. The same happens in other cases. But in all
such matters that which appears to the good man is thought to be really so. If this is correct, as it seems to be,
and virtue and the good man as such are the measure of each thing, those also will be pleasures which appear
so to him, and those things pleasant which he enjoys. If the things he finds tiresome seem pleasant to some
one, that is nothing surprising; for men may be ruined and spoilt in many ways; but the things are not
pleasant, but only pleasant to these people and to people in this condition. Those which are admittedly

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disgraceful plainly should not be said to be pleasures, except to a perverted taste; but of those that are thought
to be good what kind of pleasure or what pleasure should be said to be that proper to man? Is it not plain from
the corresponding activities? The pleasures follow these. Whether, then, the perfect and supremely happy
man has one or more activities, the pleasures that perfect these will be said in the strict sense to be pleasures
proper to man, and the rest will be so in a secondary and fractional way, as are the activities.

Now that we have spoken of the virtues, the forms of friendship, and the varieties of pleasure, what remains
is to discuss in outline the nature of happiness, since this is what we state the end of human nature to be. Our
discussion will be the more concise if we first sum up what we have said already. We said, then, that it is not
a disposition; for if it were it might belong to some one who was asleep throughout his life, living the life of a
plant, or, again, to some one who was suffering the greatest misfortunes. If these implications are
unacceptable, and we must rather class happiness as an activity, as we have said before, and if some activities
are necessary, and desirable for the sake of something else, while others are so in themselves, evidently
happiness must be placed among those desirable in themselves, not among those desirable for the sake of
something else; for happiness does not lack anything, but is self-sufficient. Now those activities are desirable
in themselves from which nothing is sought beyond the activity. And of this nature virtuous actions are
thought to be; for to do noble and good deeds is a thing desirable for its own sake.

Pleasant amusements also are thought to be of this nature; we choose them not for the sake of other things;
for we are injured rather than benefited by them, since we are led to neglect our bodies and our property. But
most of the people who are deemed happy take refuge in such pastimes, which is the reason why those who
are ready-witted at them are highly esteemed at the courts of tyrants; they make themselves pleasant
companions in the tyrants' favourite pursuits, and that is the sort of man they want. Now these things are
thought to be of the nature of happiness because people in despotic positions spend their leisure in them, but
perhaps such people prove nothing; for virtue and reason, from which good activities flow, do not depend on
despotic position; nor, if these people, who have never tasted pure and generous pleasure, take refuge in the
bodily pleasures, should these for that reason be thought more desirable; for boys, too, think the things that
are valued among themselves are the best. It is to be expected, then, that, as different things seem valuable to
boys and to men, so they should to bad men and to good. Now, as we have often maintained, those things are
both valuable and pleasant which are such to the good man; and to each man the activity in accordance with
his own disposition is most desirable, and, therefore, to the good man that which is in accordance with virtue.
Happiness, therefore, does not lie in amusement; it would, indeed, be strange if the end were amusement, and
one were to take trouble and suffer hardship all one's life in order to amuse oneself. For, in a word,
everything that we choose we choose for the sake of something else-except happiness, which is an end. Now
to exert oneself and work for the sake of amusement seems silly and utterly childish. But to amuse oneself in
order that one may exert oneself, as Anacharsis puts it, seems right; for amusement is a sort of relaxation, and
we need relaxation because we cannot work continuously. Relaxation, then, is not an end; for it is taken for
the sake of activity.

The happy life is thought to be virtuous; now a virtuous life requires exertion, and does not consist in
amusement. And we say that serious things are better than laughable things and those connected with
amusement, and that the activity of the better of any two things-whether it be two elements of our being or
two men-is the more serious; but the activity of the better is ipso facto superior and more of the nature of
happiness. And any chance person-even a slave-can enjoy the bodily pleasures no less than the best man; but
no one assigns to a slave a share in happiness-unless he assigns to him also a share in human life. For
happiness does not lie in such occupations, but, as we have said before, in virtuous activities.

If happiness is activity in accordance with virtue, it is reasonable that it should be in accordance with the
highest virtue; and this will be that of the best thing in us. Whether it be reason or something else that is this
element which is thought to be our natural ruler and guide and to take thought of things noble and divine,
whether it be itself also divine or only the most divine element in us, the activity of this in accordance with its

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proper virtue will be perfect happiness. That this activity is contemplative we have already said.

Now this would seem to be in agreement both with what we said before and with the truth. For, firstly, this
activity is the best (since not only is reason the best thing in us, but the objects of reason are the best of
knowable objects); and secondly, it is the most continuous, since we can contemplate truth more continuously
than we can do anything. And we think happiness has pleasure mingled with it, but the activity of philosophic
wisdom is admittedly the pleasantest of virtuous activities; at all events the pursuit of it is thought to offer
pleasures marvellous for their purity and their enduringness, and it is to be expected that those who know will
pass their time more pleasantly than those who inquire. And the self-sufficiency that is spoken of must
belong most to the contemplative activity. For while a philosopher, as well as a just man or one possessing
any other virtue, needs the necessaries of life, when they are sufficiently equipped with things of that sort the
just man needs people towards whom and with whom he shall act justly, and the temperate man, the brave
man, and each of the others is in the same case, but the philosopher, even when by himself, can contemplate
truth, and the better the wiser he is; he can perhaps do so better if he has fellow-workers, but still he is the
most self-sufficient. And this activity alone would seem to be loved for its own sake; for nothing arises from
it apart from the contemplating, while from practical activities we gain more or less apart from the action.
And happiness is thought to depend on leisure; for we are busy that we may have leisure, and make war that
we may live in peace. Now the activity of the practical virtues is exhibited in political or military affairs, but
the actions concerned with these seem to be unleisurely. Warlike actions are completely so (for no one
chooses to be at war, or provokes war, for the sake of being at war; any one would seem absolutely
murderous if he were to make enemies of his friends in order to bring about battle and slaughter); but the
action of the statesman is also unleisurely, and-apart from the political action itself-aims at despotic power
and honours, or at all events happiness, for him and his fellow citizens-a happiness different from political
action, and evidently sought as being different. So if among virtuous actions political and military actions are
distinguished by nobility and greatness, and these are unleisurely and aim at an end and are not desirable for
their own sake, but the activity of reason, which is contemplative, seems both to be superior in serious worth
and to aim at no end beyond itself, and to have its pleasure proper to itself (and this augments the activity),
and the self-sufficiency, leisureliness, unweariedness (so far as this is possible for man), and all the other
attributes ascribed to the supremely happy man are evidently those connected with this activity, it follows
that this will be the complete happiness of man, if it be allowed a complete term of life (for none of the
attributes of happiness is incomplete).

But such a life would be too high for man; for it is not in so far as he is man that he will live so, but in so far
as something divine is present in him; and by so much as this is superior to our composite nature is its
activity superior to that which is the exercise of the other kind of virtue. If reason is divine, then, in
comparison with man, the life according to it is divine in comparison with human life. But we must not
follow those who advise us, being men, to think of human things, and, being mortal, of mortal things, but
must, so far as we can, make ourselves immortal, and strain every nerve to live in accordance with the best
thing in us; for even if it be small in bulk, much more does it in power and worth surpass everything. This
would seem, too, to be each man himself, since it is the authoritative and better part of him. It would be
strange, then, if he were to choose not the life of his self but that of something else. And what we said before'
will apply now; that which is proper to each thing is by nature best and most pleasant for each thing; for man,
therefore, the life according to reason is best and pleasantest, since reason more than anything else is man.
This life therefore is also the happiest.

But in a secondary degree the life in accordance with the other kind of virtue is happy; for the activities in
accordance with this befit our human estate. Just and brave acts, and other virtuous acts, we do in relation to
each other, observing our respective duties with regard to contracts and services and all manner of actions
and with regard to passions; and all of these seem to be typically human. Some of them seem even to arise
from the body, and virtue of character to be in many ways bound up with the passions. Practical wisdom, too,
is linked to virtue of character, and this to practical wisdom, since the principles of practical wisdom are in

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accordance with the moral virtues and Tightness in morals is in accordance with practical wisdom. Being
connected with the passions also, the moral virtues must belong to our composite nature; and the virtues of
our composite nature are human; so, therefore, are the life and the happiness which correspond to these. The
excellence of the reason is a thing apart; we must be content to say this much about it, for to describe it
precisely is a task greater than our purpose requires. It would seem, however, also to need external equipment
but little, or less than moral virtue does. Grant that both need the necessaries, and do so equally, even if the
statesman's work is the more concerned with the body and things of that sort; for there will be little difference
there; but in what they need for the exercise of their activities there will be much difference. The liberal man
will need money for the doing of his liberal deeds, and the just man too will need it for the returning of
services (for wishes are hard to discern, and even people who are not just pretend to wish to act justly); and
the brave man will need power if he is to accomplish any of the acts that correspond to his virtue, and the
temperate man will need opportunity; for how else is either he or any of the others to be recognized? It is
debated, too, whether the will or the deed is more essential to virtue, which is assumed to involve both; it is
surely clear that its perfection involves both; but for deeds many things are needed, and more, the greater and
nobler the deeds are. But the man who is contemplating the truth needs no such thing, at least with a view to
the exercise of his activity; indeed they are, one may say, even hindrances, at all events to his contemplation;
but in so far as he is a man and lives with a number of people, he chooses to do virtuous acts; he will
therefore need such aids to living a human life.

But that perfect happiness is a contemplative activity will appear from the following consideration as well.
We assume the gods to be above all other beings blessed and happy; but what sort of actions must we assign
to them? Acts of justice? Will not the gods seem absurd if they make contracts and return deposits, and so
on? Acts of a brave man, then, confronting dangers and running risks because it is noble to do so? Or liberal
acts? To whom will they give? It will be strange if they are really to have money or anything of the kind. And
what would their temperate acts be? Is not such praise tasteless, since they have no bad appetites? If we were
to run through them all, the circumstances of action would be found trivial and unworthy of gods. Still, every
one supposes that they live and therefore that they are active; we cannot suppose them to sleep like
Endymion. Now if you take away from a living being action, and still more production, what is left but
contemplation? Therefore the activity of God, which surpasses all others in blessedness, must be
contemplative; and of human activities, therefore, that which is most akin to this must be most of the nature
of happiness.

This is indicated, too, by the fact that the other animals have no share in happiness, being completely
deprived of such activity. For while the whole life of the gods is blessed, and that of men too in so far as
some likeness of such activity belongs to them, none of the other animals is happy, since they in no way share
in contemplation. Happiness extends, then, just so far as contemplation does, and those to whom
contemplation more fully belongs are more truly happy, not as a mere concomitant but in virtue of the
contemplation; for this is in itself precious. Happiness, therefore, must be some form of contemplation.

But, being a man, one will also need external prosperity; for our nature is not self-sufficient for the purpose
of contemplation, but our body also must be healthy and must have food and other attention. Still, we must
not think that the man who is to be happy will need many things or great things, merely because he cannot be
supremely happy without external goods; for self-sufficiency and action do not involve excess, and we can
do noble acts without ruling earth and sea; for even with moderate advantages one can act virtuously (this is
manifest enough; for private persons are thought to do worthy acts no less than despots-indeed even more);
and it is enough that we should have so much as that; for the life of the man who is active in accordance with
virtue will be happy. Solon, too, was perhaps sketching well the happy man when he described him as
moderately furnished with externals but as having done (as Solon thought) the noblest acts, and lived
temperately; for one can with but moderate possessions do what one ought. Anaxagoras also seems to have
supposed the happy man not to be rich nor a despot, when he said that he would not be surprised if the happy
man were to seem to most people a strange person; for they judge by externals, since these are all they

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perceive. The opinions of the wise seem, then, to harmonize with our arguments. But while even such things
carry some conviction, the truth in practical matters is discerned from the facts of life; for these are the
decisive factor. We must therefore survey what we have already said, bringing it to the test of the facts of life,
and if it harmonizes with the facts we must accept it, but if it clashes with them we must suppose it to be
mere theory. Now he who exercises his reason and cultivates it seems to be both in the best state of mind and
most dear to the gods. For if the gods have any care for human affairs, as they are thought to have, it would
be reasonable both that they should delight in that which was best and most akin to them (i.e. reason) and that
they should reward those who love and honour this most, as caring for the things that are dear to them and
acting both rightly and nobly. And that all these attributes belong most of all to the philosopher is manifest.
He, therefore, is the dearest to the gods. And he who is that will presumably be also the happiest; so that in
this way too the philosopher will more than any other be happy.

If these matters and the virtues, and also friendship and pleasure, have been dealt with sufficiently in outline,
are we to suppose that our programme has reached its end? Surely, as the saying goes, where there are things
to be done the end is not to survey and recognize the various things, but rather to do them; with regard to
virtue, then, it is not enough to know, but we must try to have and use it, or try any other way there may be of
becoming good. Now if arguments were in themselves enough to make men good, they would justly, as
Theognis says, have won very great rewards, and such rewards should have been provided; but as things are,
while they seem to have power to encourage and stimulate the generous-minded among our youth, and to
make a character which is gently born, and a true lover of what is noble, ready to be possessed by virtue, they
are not able to encourage the many to nobility and goodness. For these do not by nature obey the sense of
shame, but only fear, and do not abstain from bad acts because of their baseness but through fear of
punishment; living by passion they pursue their own pleasures and the means to them, and and the opposite
pains, and have not even a conception of what is noble and truly pleasant, since they have never tasted it.
What argument would remould such people? It is hard, if not impossible, to remove by argument the traits
that have long since been incorporated in the character; and perhaps we must be content if, when all the
influences by which we are thought to become good are present, we get some tincture of virtue.

Now some think that we are made good by nature, others by habituation, others by teaching. Nature's part
evidently does not depend on us, but as a result of some divine causes is present in those who are truly
fortunate; while argument and teaching, we may suspect, are not powerful with all men, but the soul of the
student must first have been cultivated by means of habits for noble joy and noble hatred, like earth which is
to nourish the seed. For he who lives as passion directs will not hear argument that dissuades him, nor
understand it if he does; and how can we persuade one in such a state to change his ways? And in general
passion seems to yield not to argument but to force. The character, then, must somehow be there already with
a kinship to virtue, loving what is noble and hating what is base.

But it is difficult to get from youth up a right training for virtue if one has not been brought up under right
laws; for to live temperately and hardily is not pleasant to most people, especially when they are young. For
this reason their nurture and occupations should be fixed by law; for they will not be painful when they have
become customary. But it is surely not enough that when they are young they should get the right nurture and
attention; since they must, even when they are grown up, practise and be habituated to them, we shall need
laws for this as well, and generally speaking to cover the whole of life; for most people obey necessity rather
than argument, and punishments rather than the sense of what is noble.

This is why some think that legislators ought to stimulate men to virtue and urge them forward by the motive
of the noble, on the assumption that those who have been well advanced by the formation of habits will
attend to such influences; and that punishments and penalties should be imposed on those who disobey and
are of inferior nature, while the incurably bad should be completely banished. A good man (they think), since
he lives with his mind fixed on what is noble, will submit to argument, while a bad man, whose desire is for
pleasure, is corrected by pain like a beast of burden. This is, too, why they say the pains inflicted should be

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those that are most opposed to the pleasures such men love.

However that may be, if (as we have said) the man who is to be good must be well trained and habituated,
and go on to spend his time in worthy occupations and neither willingly nor unwillingly do bad actions, and if
this can be brought about if men live in accordance with a sort of reason and right order, provided this has
force,-if this be so, the paternal command indeed has not the required force or compulsive power (nor in
general has the command of one man, unless he be a king or something similar), but the law has compulsive
power, while it is at the same time a rule proceeding from a sort of practical wisdom and reason. And while
people hate men who oppose their impulses, even if they oppose them rightly, the law in its ordaining of what
is good is not burdensome.

In the Spartan state alone, or almost alone, the legislator seems to have paid attention to questions of nurture
and occupations; in most states such matters have been neglected, and each man lives as he pleases,
Cyclops-fashion, 'to his own wife and children dealing law'. Now it is best that there should be a public and
proper care for such matters; but if they are neglected by the community it would seem right for each man to
help his children and friends towards virtue, and that they should have the power, or at least the will, to do
this.

It would seem from what has been said that he can do this better if he makes himself capable of legislating.
For public control is plainly effected by laws, and good control by good laws; whether written or unwritten
would seem to make no difference, nor whether they are laws providing for the education of individuals or of
groups-any more than it does in the case of music or gymnastics and other such pursuits. For as in cities laws
and prevailing types of character have force, so in households do the injunctions and the habits of the father,
and these have even more because of the tie of blood and the benefits he confers; for the children start with a
natural affection and disposition to obey. Further, private education has an advantage over public, as private
medical treatment has; for while in general rest and abstinence from food are good for a man in a fever, for a
particular man they may not be; and a boxer presumably does not prescribe the same style of fighting to all
his pupils. It would seem, then, that the detail is worked out with more precision if the control is private; for
each person is more likely to get what suits his case.

But the details can be best looked after, one by one, by a doctor or gymnastic instructor or any one else who
has the general knowledge of what is good for every one or for people of a certain kind (for the sciences both
are said to be, and are, concerned with what is universal); not but what some particular detail may perhaps be
well looked after by an unscientific person, if he has studied accurately in the light of experience what
happens in each case, just as some people seem to be their own best doctors, though they could give no help
to any one else. None the less, it will perhaps be agreed that if a man does wish to become master of an art or
science he must go to the universal, and come to know it as well as possible; for, as we have said, it is with
this that the sciences are concerned.

And surely he who wants to make men, whether many or few, better by his care must try to become capable
of legislating, if it is through laws that we can become good. For to get any one whatever-any one who is put
before us-into the right condition is not for the first chance comer; if any one can do it, it is the man who
knows, just as in medicine and all other matters which give scope for care and prudence.

Must we not, then, next examine whence or how one can learn how to legislate? Is it, as in all other cases,
from statesmen? Certainly it was thought to be a part of statesmanship. Or is a difference apparent between
statesmanship and the other sciences and arts? In the others the same people are found offering to teach the
arts and practising them, e.g. doctors or painters; but while the sophists profess to teach politics, it is practised
not by any of them but by the politicians, who would seem to do so by dint of a certain skill and experience
rather than of thought; for they are not found either writing or speaking about such matters (though it were a
nobler occupation perhaps than composing speeches for the law-courts and the assembly), nor again are they

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found to have made statesmen of their own sons or any other of their friends. But it was to be expected that
they should if they could; for there is nothing better than such a skill that they could have left to their cities,
or could prefer to have for themselves, or, therefore, for those dearest to them. Still, experience seems to
contribute not a little; else they could not have become politicians by familiarity with politics; and so it seems
that those who aim at knowing about the art of politics need experience as well.

But those of the sophists who profess the art seem to be very far from teaching it. For, to put the matter
generally, they do not even know what kind of thing it is nor what kinds of things it is about; otherwise they
would not have classed it as identical with rhetoric or even inferior to it, nor have thought it easy to legislate
by collecting the laws that are thought well of; they say it is possible to select the best laws, as though even
the selection did not demand intelligence and as though right judgement were not the greatest thing, as in
matters of music. For while people experienced in any department judge rightly the works produced in it, and
understand by what means or how they are achieved, and what harmonizes with what, the inexperienced must
be content if they do not fail to see whether the work has been well or ill made-as in the case of painting.
Now laws are as it were the' works' of the political art; how then can one learn from them to be a legislator, or
judge which are best? Even medical men do not seem to be made by a study of text-books. Yet people try, at
any rate, to state not only the treatments, but also how particular classes of people can be cured and should be
treated-distinguishing the various habits of body; but while this seems useful to experienced people, to the
inexperienced it is valueless. Surely, then, while collections of laws, and of constitutions also, may be
serviceable to those who can study them and judge what is good or bad and what enactments suit what
circumstances, those who go through such collections without a practised faculty will not have right
judgement (unless it be as a spontaneous gift of nature), though they may perhaps become more intelligent in
such matters.

Now our predecessors have left the subject of legislation to us unexamined; it is perhaps best, therefore, that
we should ourselves study it, and in general study the question of the constitution, in order to complete to the
best of our ability our philosophy of human nature. First, then, if anything has been said well in detail by
earlier thinkers, let us try to review it; then in the light of the constitutions we have collected let us study what
sorts of influence preserve and destroy states, and what sorts preserve or destroy the particular kinds of
constitution, and to what causes it is due that some are well and others ill administered. When these have
been studied we shall perhaps be more likely to see with a comprehensive view, which constitution is best,
and how each must be ordered, and what laws and customs it must use, if it is to be at its best. Let us make a
beginning of our discussion.

Nicomachean Ethics 99

ON SENSE AND THE SENSIBLE

by Aristotle

ON SENSE AND THE SENSIBLE

Table of Contents

ON SENSE AND THE SENSIBLE. 1

by Aristotle 1

_1 1

2 2

_3 4

A v

_5 9

_6 12

7 15

ON SENSE AND THE SENSIBLE

by Aristotle

translated by J. I. Beare

• 1
•2
•3
•4
•5
•6

• 7

HAVING now definitely considered the soul, by itself, and its several faculties, we must next make a survey
of animals and all living things, in order to ascertain what functions are peculiar, and what functions are
common, to them. What has been already determined respecting the soul [sc. by itself] must be assumed
throughout. The remaining parts [sc. the attributes of soul and body conjointly] of our subject must be now
dealt with, and we may begin with those that come first.

The most important attributes of animals, whether common to all or peculiar to some, are, manifestly,
attributes of soul and body in conjunction, e.g. sensation, memory, passion, appetite and desire in general,
and, in addition pleasure and pain. For these may, in fact, be said to belong to all animals. But there are,
besides these, certain other attributes, of which some are common to all living things, while others are
peculiar to certain species of animals. The most important of these may be summed up in four pairs, viz.
waking and sleeping, youth and old age, inhalation and exhalation, life and death. We must endeavour to
arrive at a scientific conception of these, determining their respective natures, and the causes of their
occurrence.

But it behoves the Physical Philosopher to obtain also a clear view of the first principles of health and
disease, inasmuch as neither health nor disease can exist in lifeless things. Indeed we may say of most
physical inquirers, and of those physicians who study their art philosophically, that while the former
complete their works with a disquisition on medicine, the latter usually base their medical theories on
principles derived from Physics.

That all the attributes above enumerated belong to soul and body in conjunction, is obvious; for they all either
imply sensation as a concomitant, or have it as their medium. Some are either affections or states of
sensation, others, means of defending and safe-guarding it, while others, again, involve its destruction or
negation. Now it is clear, alike by reasoning and observation, that sensation is generated in the soul through
the medium of the body.

ON SENSE AND THE SENSIBLE 1

ON SENSE AND THE SENSIBLE

We have already, in our treatise On the Soul, explained the nature of sensation and the act of perceiving by
sense, and the reason why this affection belongs to animals. Sensation must, indeed, be attributed to all
animals as such, for by its presence or absence we distinguish essentially between what is and what is not an
animal.

But coming now to the special senses severally, we may say that touch and taste necessarily appertain to all
animals, touch, for the reason given in On the Soul, and taste, because of nutrition. It is by taste that one
distinguishes in food the pleasant from the unpleasant, so as to flee from the latter and pursue the former: and
savour in general is an affection of nutrient matter.

The senses which operate through external media, viz. smelling, hearing, seeing, are found in all animals
which possess the faculty of locomotion. To all that possess them they are a means of preservation; their final
cause being that such creatures may, guided by antecedent perception, both pursue their food, and shun things
that are bad or destructive. But in animals which have also intelligence they serve for the attainment of a
higher perfection. They bring in tidings of many distinctive qualities of things, from which the knowledge of
truth, speculative and practical, is generated in the soul.

Of the two last mentioned, seeing, regarded as a supply for the primary wants of life, and in its direct effects,
is the superior sense; but for developing intelligence, and in its indirect consequences, hearing takes the
precedence. The faculty of seeing, thanks to the fact that all bodies are coloured, brings tidings of multitudes
of distinctive qualities of all sorts; whence it is through this sense especially that we perceive the common
sensibles, viz. figure, magnitude, motion, number: while hearing announces only the distinctive qualities of
sound, and, to some few animals, those also of voice, indirectly, however, it is hearing that contributes most
to the growth of intelligence. For rational discourse is a cause of instruction in virtue of its being audible,
which it is, not directly, but indirectly; since it is composed of words, and each word is a thought-symbol.
Accordingly, of persons destitute from birth of either sense, the blind are more intelligent than the deaf and
dumb.

Of the distinctive potency of each of the faculties of sense enough has been said already.

But as to the nature of the sensory organs, or parts of the body in which each of the senses is naturally
implanted, inquirers now usually take as their guide the fundamental elements of bodies. Not, however,
finding it easy to coordinate five senses with four elements, they are at a loss respecting the fifth sense. But
they hold the organ of sight to consist of fire, being prompted to this view by a certain sensory affection of
whose true cause they are ignorant. This is that, when the eye is pressed or moved, fire appears to flash from
it. This naturally takes place in darkness, or when the eyelids are closed, for then, too, darkness is produced.

This theory, however, solves one question only to raise another; for, unless on the hypothesis that a person
who is in his full senses can see an object of vision without being aware of it, the eye must on this theory see
itself. But then why does the above affection not occur also when the eye is at rest? The true explanation of
this affection, which will contain the answer to our question, and account for the current notion that the eye
consists of fire, must be determined in the following way: Things which are smooth have the natural property
of shining in darkness, without, however, producing light. Now, the part of the eye called 'the black, i.e. its
central part, is manifestly smooth. The phenomenon of the flash occurs only when the eye is moved, because
only then could it possibly occur that the same one object should become as it were two. The rapidity of the
movement has the effect of making that which sees and that which is seen seem different from one another.
Hence the phenomenon does not occur unless the motion is rapid and takes place in darkness. For it is in the
dark that that which is smooth, e.g. the heads of certain fishes, and the sepia of the cuttle-fish, naturally

ON SENSE AND THE SENSIBLE

shines, and, when the movement of the eye is slow, it is impossible that that which sees and that which is
seen should appear to be simultaneously two and one. But, in fact, the eye sees itself in the above
phenomenon merely as it does so in ordinary optical reflexion.

If the visual organ proper really were fire, which is the doctrine of Empedocles, a doctrine taught also in the
Timaeus, and if vision were the result of light issuing from the eye as from a lantern, why should the eye not
have had the power of seeing even in the dark? It is totally idle to say, as the Timaeus does, that the visual ray
coming forth in the darkness is quenched. What is the meaning of this 'quenching' of light? That which, like a
fire of coals or an ordinary flame, is hot and dry is, indeed, quenched by the moist or cold; but heat and
dryness are evidently not attributes of light. Or if they are attributes of it, but belong to it in a degree so slight
as to be imperceptible to us, we should have expected that in the daytime the light of the sun should be
quenched when rain falls, and that darkness should prevail in frosty weather. Flame, for example, and ignited
bodies are subject to such extinction, but experience shows that nothing of this sort happens to the sunlight.

Empedocles at times seems to hold that vision is to be explained as above stated by light issuing forth from
the eye, e.g. in the following passage:-

As when one who purposes going abroad prepares a lantern,
A gleam of fire blazing through the stormy night,
Adjusting thereto, to screen it from all sorts of winds,

transparent sides,
Which scatter the breath of the winds as they blow,
While, out through them leaping, the fire,

i.e. all the more subtile part of this,
Shines along his threshold old incessant beams:
So [Divine love] embedded the round "lens", [viz.]

the primaeval fire fenced within the membranes,
In [its own] delicate tissues;
And these fended off the deep surrounding flood,
While leaping forth the fire, i.e. all its more subtile part-.

Sometimes he accounts for vision thus, but at other times he explains it by emanations from the visible
objects.

Democritus, on the other hand, is right in his opinion that the eye is of water; not, however, when he goes on
to explain seeing as mere mirroring. The mirroring that takes place in an eye is due to the fact that the eye is
smooth, and it really has its seat not in the eye which is seen, but in that which sees. For the case is merely
one of reflexion. But it would seem that even in his time there was no scientific knowledge of the general
subject of the formation of images and the phenomena of reflexion. It is strange too, that it never occurred to
him to ask why, if his theory be true, the eye alone sees, while none of the other things in which images are
reflected do so.

True, then, the visual organ proper is composed of water, yet vision appertains to it not because it is so
composed, but because it is translucent- a property common alike to water and to air. But water is more
easily confined and more easily condensed than air; wherefore it is that the pupil, i.e. the eye proper, consists
of water. That it does so is proved by facts of actual experience. The substance which flows from eyes when
decomposing is seen to be water, and this in undeveloped embryos is remarkably cold and glistening. In
sanguineous animals the white of the eye is fat and oily, in order that the moisture of the eye may be proof
against freezing. Wherefore the eye is of all parts of the body the least sensitive to cold: no one ever feels
cold in the part sheltered by the eyelids. The eyes of bloodless animals are covered with a hard scale which
gives them similar protection.

ON SENSE AND THE SENSIBLE

It is, to state the matter generally, an irrational notion that the eye should see in virtue of something issuing
from it; that the visual ray should extend itself all the way to the stars, or else go out merely to a certain point,
and there coalesce, as some say, with rays which proceed from the object. It would be better to suppose this
coalescence to take place in the fundament of the eye itself. But even this would be mere trifling. For what is
meant by the 'coalescence' of light with light? Or how is it possible? Coalescence does not occur between any
two things taken at random. And how could the light within the eye coalesce with that outside it? For the
environing membrane comes between them.

That without light vision is impossible has been stated elsewhere; but, whether the medium between the eye
and its objects is air or light, vision is caused by a process through this medium.

Accordingly, that the inner part of the eye consists of water is easily intelligible, water being translucent.

Now, as vision outwardly is impossible without [extra-organic] light, so also it is impossible inwardly
[without light within the organ]. There must, therefore, be some translucent medium within the eye, and, as
this is not air, it must be water. The soul or its perceptive part is not situated at the external surface of the eye,
but obviously somewhere within: whence the necessity of the interior of the eye being translucent, i.e.
capable of admitting light. And that it is so is plain from actual occurrences. It is matter of experience that
soldiers wounded in battle by a sword slash on the temple, so inflicted as to sever the passages of [i.e. inward
from] the eye, feel a sudden onset of darkness, as if a lamp had gone out; because what is called the pupil, i.e.
the translucent, which is a sort of inner lamp, is then cut off [from its connexion with the soul].

Hence, if the facts be at all as here stated, it is clear that- if one should explain the nature of the sensory
organs in this way, i.e. by correlating each of them with one of the four elements,- we must conceive that the
part of the eye immediately concerned in vision consists of water, that the part immediately concerned in the
perception of sound consists of air, and that the sense of smell consists of fire. (I say the sense of smell, not
the organ.) For the organ of smell is only potentially that which the sense of smell, as realized, is actually;
since the object of sense is what causes the actualization of each sense, so that it (the sense) must (at the
instant of actualization) be (actually) that which before (the moment of actualization) it was potentially. Now,
odour is a smoke-like evaporation, and smoke-like evaporation arises from fire. This also helps us to
understand why the olfactory organ has its proper seat in the environment of the brain, for cold matter is
potentially hot. In the same way must the genesis of the eye be explained. Its structure is an offshoot from the
brain, because the latter is the moistest and coldest of all the bodily parts.

The organ of touch proper consists of earth, and the faculty of taste is a particular form of touch. This
explains why the sensory organ of both touch and taste is closely related to the heart. For the heart as being
the hottest of all the bodily parts, is the counterpoise of the brain.

This then is the way in which the characteristics of the bodily organs of sense must be determined.

Of the sensibles corresponding to each sensory organ, viz. colour, sound, odour, savour, touch, we have
treated in On the Soul in general terms, having there determined what their function is, and what is implied in
their becoming actualized in relation to their respective organs. We must next consider what account we are
to give of any one of them; what, for example, we should say colour is, or sound, or odour, or savour; and so
also respecting [the object of] touch. We begin with colour.

Now, each of them may be spoken of from two points of view, i.e. either as actual or as potential. We have in
On the Soul explained in what sense the colour, or sound, regarded as actualized [for sensation] is the same

ON SENSE AND THE SENSIBLE

as, and in what sense it is different from, the correlative sensation, the actual seeing or hearing. The point of
our present discussion is, therefore, to determine what each sensible object must be in itself, in order to be
perceived as it is in actual consciousness.

We have already in On the Soul stated of Light that it is the colour of the Translucent, [being so related to it]
incidentally; for whenever a fiery element is in a translucent medium presence there is Light; while the
privation of it is Darkness. But the 'Translucent', as we call it, is not something peculiar to air, or water, or
any other of the bodies usually called translucent, but is a common 'nature' and power, capable of no separate
existence of its own, but residing in these, and subsisting likewise in all other bodies in a greater or less
degree. As the bodies in which it subsists must have some extreme bounding surface, so too must this. Here,
then, we may say that Light is a 'nature' inhering in the Translucent when the latter is without determinate
boundary. But it is manifest that, when the Translucent is in determinate bodies, its bounding extreme must
be something real; and that colour is just this 'something' we are plainly taught by facts-colour being actually
either at the external limit, or being itself that limit, in bodies. Hence it was that the Pythagoreans named the
superficies of a body its 'hue', for 'hue', indeed, lies at the limit of the body; but the limit of the body; is not a
real thing; rather we must suppose that the same natural substance which, externally, is the vehicle of colour
exists [as such a possible vehicle] also in the interior of the body.

Air and water, too [i.e. as well as determinately bounded bodies] are seen to possess colour; for their
brightness is of the nature of colour. But the colour which air or sea presents, since the body in which it
resides is not determinately bounded, is not the same when one approaches and views it close by as it is when
one regards it from a distance; whereas in determinate bodies the colour presented is definitely fixed, unless,
indeed, when the atmospheric environment causes it to change. Hence it is clear that that in them which is
susceptible of colour is in both cases the same. It is therefore the Translucent, according to the degree to
which it subsists in bodies (and it does so in all more or less), that causes them to partake of colour. But since
the colour is at the extremity of the body, it must be at the extremity of the Translucent in the body. Whence
it follows that we may define colour as the limit of the Translucent in determinately bounded body. For
whether we consider the special class of bodies called translucent, as water and such others, or determinate
bodies, which appear to possess a fixed colour of their own, it is at the exterior bounding surface that all alike
exhibit their colour.

Now, that which when present in air produces light may be present also in the Translucent which pervades
determinate bodies; or again, it may not be present, but there may be a privation of it. Accordingly, as in the
case of air the one condition is light, the other darkness, in the same way the colours White and Black are
generated in determinate bodies.

We must now treat of the other colours, reviewing the several hypotheses invented to explain their genesis.

(1) It is conceivable that the White and the Black should be juxtaposed in quantities so minute that [a particle
of] either separately would be invisible, though the joint product [of two particles, a black and a white] would
be visible; and that they should thus have the other colours for resultants. Their product could, at all events,
appear neither white nor black; and, as it must have some colour, and can have neither of these, this colour
must be of a mixed character- in fact, a species of colour different from either. Such, then, is a possible way
of conceiving the existence of a plurality of colours besides the White and Black; and we may suppose that
[of this 'plurality'] many are the result of a [numerical] ratio; for the blacks and whites may be juxtaposed in
the ratio of 3 to 2 or of 3 to 4, or in ratios expressible by other numbers; while some may be juxtaposed
according to no numerically expressible ratio, but according to some relation of excess or defect in which the
blacks and whites involved would be incommensurable quantities; and, accordingly, we may regard all these
colours [viz. all those based on numerical ratios] as analogous to the sounds that enter into music, and
suppose that those involving simple numerical ratios, like the concords in music, may be those generally
regarded as most agreeable; as, for example, purple, crimson, and some few such colours, their fewness being

ON SENSE AND THE SENSIBLE

due to the same causes which render the concords few. The other compound colours may be those which are
not based on numbers. Or it may be that, while all colours whatever [except black and white] are based on
numbers, some are regular in this respect, others irregular; and that the latter [though now supposed to be all
based on numbers] , whenever they are not pure, owe this character to a corresponding impurity in [the
arrangement of] their numerical ratios. This then is one conceivable hypothesis to explain the genesis of
intermediate colours.

(2) Another is that the Black and White appear the one through the medium of the other, giving an effect like
that sometimes produced by painters overlaying a less vivid upon a more vivid colour, as when they desire to
represent an object appearing under water or enveloped in a haze, and like that produced by the sun, which in
itself appears white, but takes a crimson hue when beheld through a fog or a cloud of smoke. On this
hypothesis, too, a variety of colours may be conceived to arise in the same way as that already described; for
between those at the surface and those underneath a definite ratio might sometimes exist; in other cases they
might stand in no determinate ratio. To [introduce a theory of colour which would set all these hypotheses
aside, and] say with the ancients that colours are emanations, and that the visibility of objects is due to such a
cause, is absurd. For they must, in any case, explain sense-perception through Touch; so that it were better to
say at once that visual perception is due to a process set up by the perceived object in the medium between
this object and the sensory organ; due, that is, to contact [with the medium affected,] not to emanations.

If we accept the hypothesis of juxtaposition, we must assume not only invisible magnitude, but also
imperceptible time, in order that the succession in the arrival of the stimulatory movements may be
unperceived, and that the compound colour seen may appear to be one, owing to its successive parts seeming
to present themselves at once. On the hypothesis of superposition, however, no such assumption is needful:
the stimulatory process produced in the medium by the upper colour, when this is itself unaffected, will be
different in kind from that produced by it when affected by the underlying colour. Hence it presents itself as a
different colour, i.e. as one which is neither white nor black. So that, if it is impossible to suppose any
magnitude to be invisible, and we must assume that there is some distance from which every magnitude is
visible, this superposition theory, too [i.e. as well as No. 3 infra], might pass as a real theory of
colour-mixture. Indeed, in the previous case also there is no reason why, to persons at a distance from the
juxtaposed blacks and whites, some one colour should not appear to present itself as a blend of both. [But it
would not be so on a nearer view], for it will be shown, in a discussion to be undertaken later on, that there is
no magnitude absolutely invisible.

(3) There is a mixture of bodies, however, not merely such as some suppose, i.e. by juxtaposition of their
minimal parts, which, owing to [the weakness of our] sense, are imperceptible by us, but a mixture by which
they [i.e. the 'matter' of which they consist] are wholly blent together by interpenetration, as we have
described it in the treatise on Mixture, where we dealt with this subject generally in its most comprehensive
aspect. For, on the supposition we are criticizing, the only totals capable of being mixed are those which are
divisible into minimal parts, [e.g. genera into individuals] as men, horses, or the [various kinds of] seeds. For
of mankind as a whole the individual man is such a least part; of horses [as an aggregate] the individual
horse. Hence by the juxtaposition of these we obtain a mixed total, consisting [like a troop of cavalry] of both
together; but we do not say that by such a process any individual man has been mixed with any individual
horse. Not in this way, but by complete interpenetration [of their matter], must we conceive those things to be
mixed which are not divisible into minima; and it is in the case of these that natural mixture exhibits itself in
its most perfect form. We have explained already in our discourse 'On Mixture' how such mixture is possible.
This being the true nature of mixture, it is plain that when bodies are mixed their colours also are necessarily
mixed at the same time; and [it is no less plain] that this is the real cause determining the existence of a
plurality of colours- not superposition or juxtaposition. For when bodies are thus mixed, their resultant
colour presents itself as one and the same at all distances alike; not varying as it is seen nearer or farther
away.

ON SENSE AND THE SENSIBLE

Colours will thus, too [as well as on the former hypotheses], be many in number on account of the fact that
the ingredients may be combined with one another in a multitude of ratios; some will be based on determinate
numerical ratios, while others again will have as their basis a relation of quantitative excess or defect not
expressible in integers. And all else that was said in reference to the colours, considered as juxtaposed or
superposed, may be said of them likewise when regarded as mixed in the way just described.

Why colours, as well as savours and sounds, consist of species determinate [in themselves] and not infinite
[in number] is a question which we shall discuss hereafter.

We have now explained what colour is, and the reason why there are many colours; while before, in our work
On the Soul, we explained the nature of sound and voice. We have next to speak of Odour and Savour, both
of which are almost the same physical affection, although they each have their being in different things.
Savours, as a class, display their nature more clearly to us than Odours, the cause of which is that the
olfactory sense of man is inferior in acuteness to that of the lower animals, and is, when compared with our
other senses, the least perfect of Man's sense of Touch, on the contrary, excels that of all other animals in
fineness, and Taste is a modification of Touch.

Now the natural substance water per se tends to be tasteless. But [since without water tasting is impossible]
either (a) we must suppose that water contains in itself [uniformly diffused through it] the various kinds of
savour, already formed, though in amounts so small as to be imperceptible, which is the doctrine of
Empedocles; or (b) the water must be a sort of matter, qualified, as it were, to produce germs of savours of all
kinds, so that all kinds of savour are generated from the water, though different kinds from its different parts,
or else (c) the water is in itself quite undifferentiated in respect of savour [whether developed or
undeveloped], but some agent, such for example as one might conceive Heat or the Sun to be, is the efficient
cause of savour.

(a) Of these three hypotheses, the falsity of that held by Empedocles is only too evident. For we see that when
pericarpal fruits are plucked [from the tree] and exposed in the sun, or subjected to the action of fire, their
sapid juices are changed by the heat, which shows that their qualities are not due to their drawing anything
from the water in the ground, but to a change which they undergo within the pericarp itself; and we see,
moreover, that these juices, when extracted and allowed to lie, instead of sweet become by lapse of time
harsh or bitter, or acquire savours of any and every sort; and that, again, by the process of boiling or
fermentation they are made to assume almost all kinds of new savours.

(b) It is likewise impossible that water should be a material qualified to generate all kinds of Savour germs
[so that different savours should arise out of different parts of the water] ; for we see different kinds of taste
generated from the same water, having it as their nutriment.

(C) It remains, therefore, to suppose that the water is changed by passively receiving some affection from an
external agent. Now, it is manifest that water does not contract the quality of sapidity from the agency of Heat
alone. For water is of all liquids the thinnest, thinner even than oil itself, though oil, owing to its viscosity, is
more ductile than water, the latter being uncohesive in its particles; whence water is more difficult than oil to
hold in the hand without spilling. But since perfectly pure water does not, when subjected to the action of
Heat, show any tendency to acquire consistency, we must infer that some other agency than heat is the cause
of sapidity. For all savours [i.e. sapid liquors] exhibit a comparative consistency. Heat is, however, a coagent
in the matter.

Now the sapid juices found in pericarpal fruits evidently exist also in the earth. Hence many of the old natural

ON SENSE AND THE SENSIBLE

philosophers assert that water has qualities like those of the earth through which it flows, a fact especially
manifest in the case of saline springs, for salt is a form of earth. Hence also when liquids are filtered through
ashes, a bitter substance, the taste they yield is bitter. There are many wells, too, of which some are bitter,
others acid, while others exhibit other tastes of all kinds.

As was to be anticipated, therefore, it is in the vegetable kingdom that tastes occur in richest variety. For, like
all things else, the Moist, by nature's law, is affected only by its contrary; and this contrary is the Dry. Thus
we see why the Moist is affected by Fire, which as a natural substance, is dry. Heat is, however, the essential
property of Fire, as Dryness is of Earth, according to what has been said in our treatise on the elements. Fire
and Earth, therefore, taken absolutely as such, have no natural power to affect, or be affected by, one another;
nor have any other pair of substances. Any two things can affect, or be affected by, one another only so far as
contrariety to the other resides in either of them.

As, therefore, persons washing Colours or Savours in a liquid cause the water in which they wash to acquire
such a quality [as that of the colour or savour], so nature, too, by washing the Dry and Earthy in the Moist,
and by filtering the latter, that is, moving it on by the agency of heat through the dry and earthy, imparts to it
a certain quality. This affection, wrought by the aforesaid Dry in the Moist, capable of transforming the sense
of Taste from potentiality to actuality, is Savour. Savour brings into actual exercise the perceptive faculty
which pre-existed only in potency. The activity of sense-perception in general is analogous, not to the
process of acquiring knowledge, but to that of exercising knowledge already acquired.

That Savours, either as a quality or as the privation of a quality, belong not to every form of the Dry but to the
Nutrient, we shall see by considering that neither the Dry without the Moist, nor the Moist without the Dry, is
nutrient. For no single element, but only composite substance, constitutes nutriment for animals. Now, among
the perceptible elements of the food which animals assimilate, the tangible are the efficient causes of growth
and decay; it is qua hot or cold that the food assimilated causes these; for the heat or cold is the direct cause
of growth or decay. It is qua gustable, however, that the assimilated food supplies nutrition. For all organisms
are nourished by the Sweet [i.e. the 'gustable' proper], either by itself or in combination with other savours.
Of this we must speak with more precise detail in our work on Generation: for the present we need touch
upon it only so far as our subject here requires. Heat causes growth, and fits the food-stuff for alimentation;
it attracts [into the organic system] that which is light [viz. the sweet], while the salt and bitter it rejects
because of their heaviness. In fact, whatever effects external heat produces in external bodies, the same are
produced by their internal heat in animal and vegetable organisms. Hence it is [i.e. by the agency of heat as
described] that nourishment is effected by the sweet. The other savours are introduced into and blended in
food [naturally] on a principle analogous to that on which the saline or the acid is used artificially, i.e. for
seasoning. These latter are used because they counteract the tendency of the sweet to be too nutrient, and to
float on the stomach.

As the intermediate colours arise from the mixture of white and black, so the intermediate savours arise from
the Sweet and Bitter; and these savours, too, severally involve either a definite ratio, or else an indefinite
relation of degree, between their components, either having certain integral numbers at the basis of their
mixture, and, consequently, of their stimulative effect, or else being mixed in proportions not arithmetically
expressible. The tastes which give pleasure in their combination are those which have their components
joined in a definite ratio.

The sweet taste alone is Rich, [therefore the latter may be regarded as a variety of the former], while [so far
as both imply privation of the Sweet] the Saline is fairly identical with the Bitter. Between the extremes of
sweet and bitter come the Harsh, the Pungent, the Astringent, and the Acid. Savours and Colours, it will be
observed, contain respectively about the same number of species. For there are seven species of each, if, as is
reasonable, we regard Dun [or Grey] as a variety of Black (for the alternative is that Yellow should be classed
with White, as Rich with Sweet); while [the irreducible colours, viz.] Crimson, Violet, leek-Green, and deep

4 8

ON SENSE AND THE SENSIBLE

Blue, come between White and Black, and from these all others are derived by mixture.

Again, as Black is a privation of White in the Translucent, so Saline or Bitter is a privation of Sweet in the
Nutrient Moist. This explains why the ash of all burnt things is bitter; for the potable [sc. the sweet] moisture
has been exuded from them.

Democritus and most of the natural philosophers who treat of sense-perception proceed quite irrationally, for
they represent all objects of sense as objects of Touch. Yet, if this is really so, it clearly follows that each of
the other senses is a mode of Touch; but one can see at a glance that this is impossible.

Again, they treat the percepts common to all senses as proper to one. For [the qualities by which they explain
taste viz.] Magnitude and Figure, Roughness and Smoothness, and, moreover, the Sharpness and Bluntness
found in solid bodies, are percepts common to all the senses, or if not to all, at least to Sight and Touch. This
explains why it is that the senses are liable to err regarding them, while no such error arises respecting their
proper sensibles; e.g. the sense of Seeing is not deceived as to Colour, nor is that of Hearing as to Sound.

On the other hand, they reduce the proper to common sensibles, as Democritus does with White and Black;
for he asserts that the latter is [a mode of the] rough, and the former [a mode of the] smooth, while he reduces
Savours to the atomic figures. Yet surely no one sense, or, if any, the sense of Sight rather than any other, can
discern the common sensibles. But if we suppose that the sense of Taste is better able to do so, then- since to
discern the smallest objects in each kind is what marks the acutest sense-Taste should have been the sense
which best perceived the common sensibles generally, and showed the most perfect power of discerning
figures in general.

Again, all the sensibles involve contrariety; e.g. in Colour White is contrary to Black, and in Savours Bitter is
contrary to Sweet; but no one figure is reckoned as contrary to any other figure. Else, to which of the possible
polygonal figures [to which Democritus reduces Bitter] is the spherical figure [to which he reduces Sweet]
contrary?

Again, since figures are infinite in number, savours also should be infinite; [the possible rejoinder- 'that they
are so, only that some are not perceived'- cannot be sustained] for why should one savour be perceived, and
another not?

This completes our discussion of the object of Taste, i.e. Savour; for the other affections of Savours are
examined in their proper place in connection with the natural history of Plants.

Our conception of the nature of Odours must be analogous to that of Savours; inasmuch as the Sapid Dry
effects in air and water alike, but in a different province of sense, precisely what the Dry effects in the Moist
of water only. We customarily predicate Translucency of both air and water in common; but it is not qua
translucent that either is a vehicle of odour, but qua possessed of a power of washing or rinsing [and so
imbibing] the Sapid Dryness.

For the object of Smell exists not in air only: it also exists in water. This is proved by the case of fishes and
testacea, which are seen to possess the faculty of smell, although water contains no air (for whenever air is
generated within water it rises to the surface), and these creatures do not respire. Hence, if one were to
assume that air and water are both moist, it would follow that Odour is the natural substance consisting of the
Sapid Dry diffused in the Moist, and whatever is of this kind would be an object of Smell.

ON SENSE AND THE SENSIBLE

That the property of odorousness is based upon the Sapid may be seen by comparing the things which possess
with those which do not possess odour. The elements, viz. Fire, Air, Earth, Water, are inodorous, because
both the dry and the moist among them are without sapidity, unless some added ingredient produces it. This
explains why sea-water possesses odour, for [unlike 'elemental' water] it contains savour and dryness. Salt,
too, is more odorous than natron, as the oil which exudes from the former proves, for natron is allied to
['elemental'] earth more nearly than salt. Again, a stone is inodorous, just because it is tasteless, while, on the
contrary, wood is odorous, because it is sapid. The kinds of wood, too, which contain more ['elemental']
water are less odorous than others. Moreover, to take the case of metals, gold is inodorous because it is
without taste, but bronze and iron are odorous; and when the [sapid] moisture has been burnt out of them,
their slag is, in all cases, less odorous the metals [than the metals themselves]. Silver and tin are more
odorous than the one class of metals, less so than the other, inasmuch as they are water [to a greater degree
than the former, to a less degree than the latter].

Some writers look upon Fumid exhalation, which is a compound of Earth and Air, as the essence of Odour.
[Indeed all are inclined to rush to this theory of Odour.] Heraclitus implied his adherence to it when he
declared that if all existing things were turned into Smoke, the nose would be the organ to discern them with.
All writers incline to refer odour to this cause [sc. exhalation of some sort], but some regard it as aqueous,
others as fumid, exhalation; while others, again, hold it to be either. Aqueous exhalation is merely a form of
moisture, but fumid exhalation is, as already remarked, composed of Air and Earth. The former when
condensed turns into water; the latter, in a particular species of earth. Now, it is unlikely that odour is either
of these. For vaporous exhalation consists of mere water [which, being tasteless, is inodorous] ; and fumid
exhalation cannot occur in water at all, though, as has been before stated, aquatic creatures also have the
sense of smell.

Again, the exhalation theory of odour is analogous to the theory of emanations. If, therefore, the latter is
untenable, so, too, is the former.

It is clearly conceivable that the Moist, whether in air (for air, too, is essentially moist) or in water, should
imbibe the influence of, and have effects wrought in it by, the Sapid Dryness. Moreover, if the Dry produces
in moist media, i.e. water and air, an effect as of something washed out in them, it is manifest that odours
must be something analogous to savours. Nay, indeed, this analogy is, in some instances, a fact [registered in
language] ; for odours as well as savours are spoken of as pungent, sweet, harsh, astringent rich [='savoury T ] ;
and one might regard fetid smells as analogous to bitter tastes; which explains why the former are offensive
to inhalation as the latter are to deglutition. It is clear, therefore, that Odour is in both water and air what
Savour is in water alone. This explains why coldness and freezing render Savours dull, and abolish odours
altogether; for cooling and freezing tend to annul the kinetic heat which helps to fabricate sapidity.

There are two species of the Odorous. For the statement of certain writers that the odorous is not divisible
into species is false; it is so divisible. We must here define the sense in which these species are to be admitted
or denied.

One class of odours, then, is that which runs parallel, as has been observed, to savours: to odours of this class
their pleasantness or unpleasantness belongs incidentally. For owing to the fact that Savours are qualities of
nutrient matter, the odours connected with these [e.g. those of a certain food] are agreeable as long as animals
have an appetite for the food, but they are not agreeable to them when sated and no longer in want of it; nor
are they agreeable, either, to those animals that do not like the food itself which yields the odours. Hence, as
we observed, these odours are pleasant or unpleasant incidentally, and the same reasoning explains why it is
that they are perceptible to all animals in common.

The other class of odours consists of those agreeable in their essential nature, e.g. those of flowers. For these
do not in any degree stimulate animals to food, nor do they contribute in any way to appetite; their effect

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ON SENSE AND THE SENSIBLE

upon it, if any, is rather the opposite. For the verse of Strattis ridiculing Euripides-
Use not perfumery to flavour soup,
contains a truth.

Those who nowadays introduce such flavours into beverages deforce our sense of pleasure by habituating us
to them, until, from two distinct kinds of sensations combined, pleasure arises as it might from one simple
kind.

Of this species of odour man alone is sensible; the other, viz. that correlated with Tastes, is, as has been said
before, perceptible also to the lower animals. And odours of the latter sort, since their pleasureableness
depends upon taste, are divided into as many species as there are different tastes; but we cannot go on to say
this of the former kind of odour, since its nature is agreeable or disagreeable per se. The reason why the
perception of such odours is peculiar to man is found in the characteristic state of man's brain. For his brain is
naturally cold, and the blood which it contains in its vessels is thin and pure but easily cooled (whence it
happens that the exhalation arising from food, being cooled by the coldness of this region, produces
unhealthy rheums); therefore it is that odours of such a species have been generated for human beings, as a
safeguard to health. This is their sole function, and that they perform it is evident. For food, whether dry or
moist, though sweet to taste, is often unwholesome; whereas the odour arising from what is fragrant, that
odour which is pleasant in its own right, is, so to say, always beneficial to persons in any state of bodily
health whatever.

For this reason, too, the perception of odour [in general] effected through respiration, not in all animals, but
in man and certain other sanguineous animals, e.g. quadrupeds, and all that participate freely in the natural
substance air; because when odours, on account of the lightness of the heat in them, mount to the brain, the
health of this region is thereby promoted. For odour, as a power, is naturally heat-giving. Thus Nature has
employed respiration for two purposes: primarily for the relief thereby brought to the thorax, secondarily for
the inhalation of odour. For while an animal is inhaling,- odour moves in through its nostrils, as it were 'from
a side-entrance.'

But the perception of the second class of odours above described [does not belong to all animal, but] is
confined to human beings, because man's brain is, in proportion to his whole bulk, larger and moister than the
brain of any other animal. This is the reason of the further fact that man alone, so to speak, among animals
perceives and takes pleasure in the odours of flowers and such things. For the heat and stimulation set up by
these odours are commensurate with the excess of moisture and coldness in his cerebral region. On all the
other animals which have lungs, Nature has bestowed their due perception of one of the two kinds of odour
[i.e. that connected with nutrition] through the act of respiration, guarding against the needless creation of
two organs of sense; for in the fact that they respire the other animals have already sufficient provision for
their perception of the one species of odour only, as human beings have for their perception of both.

But that creatures which do not respire have the olfactory sense is evident. For fishes, and all insects as a
class, have, thanks to the species of odour correlated with nutrition, a keen olfactory sense of their proper
food from a distance, even when they are very far away from it; such is the case with bees, and also with the
class of small ants, which some denominate knipes. Among marine animals, too, the murex and many other
similar animals have an acute perception of their food by its odour.

It is not equally certain what the organ is whereby they so perceive. This question, of the organ whereby they
perceive odour, may well cause a difficulty, if we assume that smelling takes place in animals only while
respiring (for that this is the fact is manifest in all the animals which do respire), whereas none of those just
mentioned respires, and yet they have the sense of smell- unless, indeed, they have some other sense not

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ON SENSE AND THE SENSIBLE

included in the ordinary five. This supposition is, however, impossible. For any sense which perceives odour
is a sense of smell, and this they do perceive, though probably not in the same way as creatures which respire,
but when the latter are respiring the current of breath removes something that is laid like a lid upon the organ
proper (which explains why they do not perceive odours when not respiring); while in creatures which do not
respire this is always off: just as some animals have eyelids on their eyes, and when these are not raised they
cannot see, whereas hard-eyed animals have no lids, and consequently do not need, besides eyes, an agency
to raise the lids, but see straightway [without intermission] from the actual moment at which it is first
possible for them to do so [i.e. from the moment when an object first comes within their field of vision].

Consistently with what has been said above, not one of the lower animals shows repugnance to the odour of
things which are essentially ill-smelling, unless one of the latter is positively pernicious. They are destroyed,
however, by these things, just as human beings are; i.e. as human beings get headaches from, and are often
asphyxiated by, the fumes of charcoal, so the lower animals perish from the strong fumes of brimstone and
bituminous substances; and it is owing to experience of such effects that they shun these. For the disagreeable
odour in itself they care nothing whatever (though the odours of many plants are essentially disagreeable),
unless, indeed, it has some effect upon the taste of their food.

The senses making up an odd number, and an odd number having always a middle unit, the sense of smell
occupies in itself as it were a middle position between the tactual senses, i.e. Touch and Taste, and those
which perceive through a medium, i.e. Sight and Hearing. Hence the object of smell, too, is an affection of
nutrient substances (which fall within the class of Tangibles), and is also an affection of the audible and the
visible; whence it is that creatures have the sense of smell both in air and water. Accordingly, the object of
smell is something common to both of these provinces, i.e. it appertains both to the tangible on the one hand,
and on the other to the audible and translucent. Hence the propriety of the figure by which it has been
described by us as an immersion or washing of dryness in the Moist and Fluid. Such then must be our
account of the sense in which one is or is not entitled to speak of the odorous as having species.

The theory held by certain of the Pythagoreans, that some animals are nourished by odours alone, is unsound.
For, in the first place, we see that food must be composite, since the bodies nourished by it are not simple.
This explains why waste matter is secreted from food, either within the organisms, or, as in plants, outside
them. But since even water by itself alone, that is, when unmixed, will not suffice for food- for anything
which is to form a consistency must be corporeal-, it is still much less conceivable that air should be so
corporealized [and thus fitted to be food]. But, besides this, we see that all animals have a receptacle for food,
from which, when it has entered, the body absorbs it. Now, the organ which perceives odour is in the head,
and odour enters with the inhalation of the breath; so that it goes to the respiratory region. It is plain,
therefore, that odour, qua odour, does not contribute to nutrition; that, however, it is serviceable to health is
equally plain, as well by immediate perception as from the arguments above employed; so that odour is in
relation to general health what savour is in the province of nutrition and in relation to the bodies nourished.

This then must conclude our discussion of the several organs of sense-perception.

One might ask: if every body is infinitely divisible, are its sensible qualities- Colour, Savour, Odour, Sound,
Weight, Cold or Heat, [Heaviness or] Lightness, Hardness or Softness-also infinitely divisible? Or, is this
impossible?

[One might well ask this question], because each of them is productive of sense-perception, since, in fact, all
derive their name [of 'sensible qualities'] from the very circumstance of their being able to stimulate this.
Hence, [if this is so] both our perception of them should likewise be divisible to infinity, and every part of a

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ON SENSE AND THE SENSIBLE

body [however small] should be a perceptible magnitude. For it is impossible, e.g. to see a thing which is
white but not of a certain magnitude.

Since if it were not so, [if its sensible qualities were not divisible, pari passu with body], we might conceive a
body existing but having no colour, or weight, or any such quality; accordingly not perceptible at all. For
these qualities are the objects of sense-perception. On this supposition, every perceptible object should be
regarded as composed not of perceptible [but of imperceptible] parts. Yet it must [be really composed of
perceptible parts], since assuredly it does not consist of mathematical [and therefore purely abstract and
non-sensible] quantities. Again, by what faculty should we discern and cognize these [hypothetical real
things without sensible qualities]? Is it by Reason? But they are not objects of Reason; nor does reason
apprehend objects in space, except when it acts in conjunction with sense-perception. At the same time, if
this be the case [that there are magnitudes, physically real, but without sensible quality], it seems to tell in
favour of the atomistic hypothesis; for thus, indeed, [by accepting this hypothesis], the question [with which
this chapter begins] might be solved [negatively]. But it is impossible [to accept this hypothesis]. Our views
on the subject of atoms are to be found in our treatise on Movement.

The solution of these questions will bring with it also the answer to the question why the species of Colour,
Taste, Sound, and other sensible qualities are limited. For in all classes of things lying between extremes the
intermediates must be limited. But contraries are extremes, and every object of sense-perception involves
contrariety: e.g. in Colour, White x Black; in Savour, Sweet x Bitter, and in all the other sensibles also the
contraries are extremes. Now, that which is continuous is divisible into an infinite number of unequal parts,
but into a finite number of equal parts, while that which is not per se continuous is divisible into species
which are finite in number. Since then, the several sensible qualities of things are to be reckoned as species,
while continuity always subsists in these, we must take account of the difference between the Potential and
the Actual. It is owing to this difference that we do not [actually] see its ten-thousandth part in a grain of
millet, although sight has embraced the whole grain within its scope; and it is owing to this, too, that the
sound contained in a quarter-tone escapes notice, and yet one hears the whole strain, inasmuch as it is a
continuum; but the interval between the extreme sounds [that bound the quarter-tone] escapes the ear [being
only potentially audible, not actually]. So, in the case of other objects of sense, extremely small constituents
are unnoticed; because they are only potentially not actually [perceptible e.g.] visible, unless when they have
been parted from the wholes. So the footlength too exists potentially in the two-foot length, but actually only
when it has been separated from the whole. But objective increments so small as those above might well, if
separated from their totals, [instead of achieving 'actual' exisistence] be dissolved in their environments, like
a drop of sapid moisture poured out into the sea. But even if this were not so [sc. with the objective
magnitude], still, since the [subjective] of sense-perception is not perceptible in itself, nor capable of separate
existence (since it exists only potentially in the more distinctly perceivable whole of sense-perception), so
neither will it be possible to perceive [actually] its correlatively small object [sc. its quantum of pathema or
sensible quality] when separated from the object-total. But yet this [small object] is to be considered as
perceptible: for it is both potentially so already [i.e. even when alone], and destined to be actually so when it
has become part of an aggregate. Thus, therefore, we have shown that some magnitudes and their sensible
qualities escape notice, and the reason why they do so, as well as the manner in which they are still
perceptible or not perceptible in such cases. Accordingly then when these [minutely subdivided] sensibles
have once again become aggregated in a whole in such a manner, relatively to one another, as to be
perceptible actually, and not merely because they are in the whole, but even apart from it, it follows
necessarily [from what has been already stated] that their sensible qualities, whether colours or tastes or
sounds, are limited in number.

One might ask:- do the objects of sense-perception, or the movements proceeding from them ([since
movements there are,] in whichever of the two ways [viz. by emanations or by stimulatory kinesis]
sense-perception takes place), when these are actualized for perception, always arrive first at a spatial middle
point [between the sense-organ and its object], as Odour evidently does, and also Sound? For he who is

6 13

ON SENSE AND THE SENSIBLE

nearer [to the odorous object] perceives the Odour sooner [than who is farther away], and the Sound of a
stroke reaches us some time after it has been struck. Is it thus also with an object seen, and with Light?
Empedocles, for example, says that the Light from the Sun arrives first in the intervening space before it
comes to the eye, or reaches the Earth. This might plausibly seem to be the case. For whatever is moved [in
space] , is moved from one place to another; hence there must be a corresponding interval of time also in
which it is moved from the one place to the other. But any given time is divisible into parts; so that we should
assume a time when the sun's ray was not as yet seen, but was still travelling in the middle space.

Now, even if it be true that the acts of 'hearing' and 'having heard', and, generally, those of 'perceiving' and
'having perceived', form co-instantaneous wholes, in other words, that acts of sense-perception do not
involve a process of becoming, but have their being none the less without involving such a process; yet, just
as, [in the case of sound], though the stroke which causes the Sound has been already struck, the Sound is not
yet at the ear (and that this last is a fact is further proved by the transformation which the letters [viz. the
consonants as heard] undergo [in the case of words spoken from a distance], implying that the local
movement [involved in Sound] takes place in the space between [us and the speaker] ; for the reason why
[persons addressed from a distance] do not succeed in catching the sense of what is said is evidently that the
air [sound wave] in moving towards them has its form changed) [granting this, then, the question arises] : is
the same also true in the case of Colour and Light? For certainly it is not true that the beholder sees, and the
object is seen, in virtue of some merely abstract relationship between them, such as that between equals. For
if it were so, there would be no need [as there is] that either [the beholder or the thing beheld] should occupy
some particular place; since to the equalization of things their being near to, or far from, one another makes
no difference.

Now this [travelling through successive positions in the medium] may with good reason take place as regards
Sound and Odour, for these, like [their media] Air and Water, are continuous, but the movement of both is
divided into parts. This too is the ground of the fact that the object which the person first in order of
proximity hears or smells is the same as that which each subsequent person perceives, while yet it is not the
same.

Some, indeed, raise a question also on these very points; they declare it impossible that one person should
hear, or see, or smell, the same object as another, urging the impossibility of several persons in different
places hearing or smelling [the same object], for the one same thing would [thus] be divided from itself. The
answer is that, in perceiving the object which first set up the motion- e.g. a bell, or frankincense, or fire- all
perceive an object numerically one and the same; while, of course, in the special object perceived they
perceive an object numerically different for each, though specifically the same for all; and this, accordingly,
explains how it is that many persons together see, or smell, or hear [the same object]. These things [the odour
or sound proper] are not bodies, but an affection or process of some kind (otherwise this [viz. simultaneous
perception of the one object by many] would not have been, as it is, a fact of experience) though, on the other
hand, they each imply a body [as their cause].

But [though sound and odour may travel,] with regard to Light the case is different. For Light has its raison
d'etre in the being [not becoming] of something, but it is not a movement. And in general, even in qualitative
change the case is different from what it is in local movement [both being different species of kinesis]. Local
movements, of course, arrive first at a point midway before reaching their goal (and Sound, it is currently
believed, is a movement of something locally moved), but we cannot go on to assert this [arrival at a point
midway] like manner of things which undergo qualitative change. For this kind of change may conceivably
take place in a thing all at once, without one half of it being changed before the other; e.g. it is conceivable
that water should be frozen simultaneously in every part. But still, for all that, if the body which is heated or
frozen is extensive, each part of it successively is affected by the part contiguous, while the part first changed
in quality is so changed by the cause itself which originates the change, and thus the change throughout the
whole need not take place coinstantaneously and all at once. Tasting would have been as smelling now is, if

6 14

ON SENSE AND THE SENSIBLE

we lived in a liquid medium, and perceived [the sapid object] at a distance, before touching it.

Naturally, then, the parts of media between a sensory organ and its object are not all affected at once- except
in the case of Light [illumination] for the reason above stated, and also in the case of seeing, for the same
reason; for Light is an efficient cause of seeing.

Another question respecting sense-perception is as follows: assuming, as is natural, that of two
[simultaneous] sensory stimuli the stronger always tends to extrude the weaker [from consciousness] , is it
conceivable or not that one should be able to discern two objects coinstantaneously in the same individual
time? The above assumption explains why persons do not perceive what is brought before their eyes, if they
are at the time deep in thought, or in a fright, or listening to some loud noise. This assumption, then, must be
made, and also the following: that it is easier to discern each object of sense when in its simple form than
when an ingredient in a mixture; easier, for example, to discern wine when neat than when blended, and so
also honey, and [in other provinces] a colour, or to discern the nete by itself alone, than [when sounded with
the hypate] in the octave; the reason being that component elements tend to efface [the distinctive
characteristics of] one another. Such is the effect [on one another] of all ingredients of which, when
compounded, some one thing is formed.

If, then, the greater stimulus tends to expel the less, it necessarily follows that, when they concur, this greater
should itself too be less distinctly perceptible than if it were alone, since the less by blending with it has
removed some of its individuality, according to our assumption that simple objects are in all cases more
distinctly perceptible.

Now, if the two stimuli are equal but heterogeneous, no perception of either will ensue; they will alike efface
one another's characteristics. But in such a case the perception of either stimulus in its simple form is
impossible. Hence either there will then be no sense-perception at all, or there will be a perception
compounded of both and differing from either. The latter is what actually seems to result from ingredients
blended together, whatever may be the compound in which they are so mixed.

Since, then, from some concurrent [sensory stimuli] a resultant object is produced, while from others no such
resultant is produced, and of the latter sort are those things which belong to different sense provinces (for
only those things are capable of mixture whose extremes are contraries, and no one compound can be formed
from, e.g. White and Sharp, except indirectly, i.e. not as a concord is formed of Sharp and Grave); there
follows logically the impossibility of discerning such concurrent stimuli coinstantaneously. For we must
suppose that the stimuli, when equal, tend alike to efface one another, since no one [form of stimulus] results
from them; while, if they are unequal, the stronger alone is distinctly perceptible.

Again, the soul would be more likely to perceive coinstantaneously, with one and the same sensory act, two
things in the same sensory province, such as the Grave and the Sharp in sound; for the sensory stimulation in
this one province is more likely to be unitemporal than that involving two different provinces, as Sight and
Hearing. But it is impossible to perceive two objects coinstantaneously in the same sensory act unless they
have been mixed, [when, however, they are no longer two], for their amalgamation involves their becoming
one, and the sensory act related to one object is itself one, and such act, when one, is, of course,
coinstantaneous with itself. Hence, when things are mixed we of necessity perceive them coinstantaneously:
for we perceive them by a perception actually one. For an object numerically one means that which is
perceived by a perception actually one, whereas an object specifically one means that which is perceived by a
sensory act potentially one [i.e. by an energeia of the same sensuous faculty]. If then the actualized
perception is one, it will declare its data to be one object; they must, therefore, have been mixed.

7 15

ON SENSE AND THE SENSIBLE

Accordingly, when they have not been mixed, the actualized perceptions which perceive them will be two;
but [if so, their perception must be successive not coinstantaneous, for] in one and the same faculty the
perception actualized at any single moment is necessarily one, only one stimulation or exertion of a single
faculty being possible at a single instant, and in the case supposed here the faculty is one. It follows,
therefore, that we cannot conceive the possibility of perceiving two distinct objects coinstantaneously with
one and the same sense.

But if it be thus impossible to perceive coinstantaneously two objects in the same province of sense if they
are really two, manifestly it is still less conceivable that we should perceive coinstantaneously objects in two
different sensory provinces, as White and Sweet. For it appears that when the Soul predicates numerical unity
it does so in virtue of nothing else than such coinstantaneous perception [of one object, in one instant, by one
energeia] : while it predicates specific unity in virtue of [the unity of] the discriminating faculty of sense
together with [the unity of] the mode in which this operates. What I mean, for example, is this; the same
sense no doubt discerns White and Black, [which are hence generically one] though specifically different
from one another, and so, too, a faculty of sense self-identical, but different from the former, discerns Sweet
and Bitter; but while both these faculties differ from one another [and each from itself] in their modes of
discerning either of their respective contraries, yet in perceiving the co-ordinates in each province they
proceed in manners analogous to one another; for instance, as Taste perceives Sweet, so Sight perceives
White; and as the latter perceives Black, so the former perceives Bitter.

Again, if the stimuli of sense derived from Contraries are themselves Contrary, and if Contraries cannot be
conceived as subsisting together in the same individual subject, and if Contraries, e.g. Sweet and Bitter, come
under one and the same sense-faculty, we must conclude that it is impossible to discern them
coinstantaneously. It is likewise clearly impossible so to discern such homogeneous sensibles as are not
[indeed] Contrary, [but are yet of different species]. For these are, [in the sphere of colour, for instance],
classed some with White, others with Black, and so it is, likewise, in the other provinces of sense; for
example, of savours, some are classed with Sweet, and others with Bitter. Nor can one discern the
components in compounds coinstantaneously (for these are ratios of Contraries, as e.g. the Octave or the
Fifth); unless, indeed, on condition of perceiving them as one. For thus, and not otherwise, the ratios of the
extreme sounds are compounded into one ratio: since we should have together the ratio, on the one hand, of
Many to Few or of Odd to Even, on the other, that of Few to Many or of Even to Odd [and these, to be
perceived together, must be unified] .

If, then, the sensibles denominated co-ordinates though in different provinces of sense (e.g. I call Sweet and
White co-ordinates though in different provinces) stand yet more aloof, and differ more, from one another
than do any sensibles in the same province; while Sweet differs from White even more than Black does from
White, it is still less conceivable that one should discern them [viz. sensibles in different sensory provinces
whether co-ordinates or not] coinstantaneously than sensibles which are in the same province. Therefore, if
coinstantaneous perception of the latter be impossible, that of the former is a fortiori impossible.

Some of the writers who treat of concords assert that the sounds combined in these do not reach us
simultaneously, but only appear to do so, their real successiveness being unnoticed whenever the time it
involves is [so small as to be] imperceptible. Is this true or not? One might perhaps, following this up, go so
far as to say that even the current opinion that one sees and hears coinstantaneously is due merely to the fact
that the intervals of time [between the really successive perceptions of sight and hearing] escape observation.
But this can scarcely be true, nor is it conceivable that any portion of time should be [absolutely]
imperceptible, or that any should be absolutely unnoticeable; the truth being that it is possible to perceive
every instant of time. [This is so] ; because, if it is inconceivable that a person should, while perceiving
himself or aught else in a continuous time, be at any instant unaware of his own existence; while, obviously,
the assumption, that there is in the time-continuum a time so small as to be absolutely imperceptible, carries
the implication that a person would, during such time, be unaware of his own existence, as well as of his

7 16

ON SENSE AND THE SENSIBLE

seeing and perceiving; [this assumption must be false].

Again, if there is any magnitude, whether time or thing, absolutely imperceptible owing to its smallness, it
follows that there would not be either a thing which one perceives, or a time in which one perceives it, unless
in the sense that in some part of the given time he sees some part of the given thing. For [let there be a line
ab, divided into two parts at g, and let this line represent a whole object and a corresponding whole time.
Now,] if one sees the whole line, and perceives it during a time which forms one and the same continuum,
only in the sense that he does so in some portion of this time, let us suppose the part gb, representing a time
in which by supposition he was perceiving nothing, cut off from the whole. Well, then, he perceives in a
certain part [viz. in the remainder] of the time, or perceives a part [viz. the remainder] of the line, after the
fashion in which one sees the whole earth by seeing some given part of it, or walks in a year by walking in
some given part of the year. But [by hypothesis] in the part bg he perceives nothing: therefore, in fact, he is
said to perceive the whole object and during the whole time simply because he perceives [some part of the
object] in some part of the time ab. But the same argument holds also in the case of ag [the remainder,
regarded in its turn as a whole] ; for it will be found [on this theory of vacant times and imperceptible
magnitudes] that one always perceives only in some part of a given whole time, and perceives only some part
of a whole magnitude, and that it is impossible to perceive any [really] whole [object in a really whole time; a
conclusion which is absurd, as it would logically annihilate the perception of both Objects and Time].

Therefore we must conclude that all magnitudes are perceptible, but their actual dimensions do not present
themselves immediately in their presentation as objects. One sees the sun, or a four-cubit rod at a distance, as
a magnitude, but their exact dimensions are not given in their visual presentation: nay, at times an object of
sight appears indivisible, but [vision like other special senses, is fallible respecting 'common sensibles', e.g.
magnitude, and] nothing that one sees is really indivisible. The reason of this has been previously explained.
It is clear then, from the above arguments, that no portion of time is imperceptible.

But we must here return to the question proposed above for discussion, whether it is possible or impossible to
perceive several objects coinstantaneously; by 'coinstantaneously' I mean perceiving the several objects in a
time one and indivisible relatively to one another, i.e. indivisible in a sense consistent with its being all a
continuum.

First, then, is it conceivable that one should perceive the different things coinstantaneously, but each with a
different part of the Soul? Or [must we object] that, in the first place, to begin with the objects of one and the
same sense, e.g. Sight, if we assume it [the Soul qua exercising Sight] to perceive one colour with one part,
and another colour with a different part, it will have a plurality of parts the same in species, [as they must be,]
since the objects which it thus perceives fall within the same genus?

Should any one [to illustrate how the Soul might have in it two different parts specifically identical, each
directed to a set of aistheta the same in genus with that to which the other is directed] urge that, as there are
two eyes, so there may be in the Soul something analogous, [the reply is] that of the eyes, doubtless, some
one organ is formed, and hence their actualization in perception is one; but if this is so in the Soul, then, in so
far as what is formed of both [i.e. of any two specifically identical parts as assumed] is one, the true
perceiving subject also will be one, [and the contradictory of the above hypothesis (of different parts of Soul
remaining engaged in simultaneous perception with one sense) is what emerges from the analogy] ; while if
the two parts of Soul remain separate, the analogy of the eyes will fail, [for of these some one is really
formed].

Furthermore, [on the supposition of the need of different parts of Soul, co-operating in each sense, to discern
different objects coinstantaneously], the senses will be each at the same time one and many, as if we should
say that they were each a set of diverse sciences; for neither will an 'activity' exist without its proper faculty,
nor without activity will there be sensation.

7 17

ON SENSE AND THE SENSIBLE

But if the Soul does not, in the way suggested [i.e. with different parts of itself acting simultaneously],
perceive in one and the same individual time sensibles of the same sense, a fortiori it is not thus that it
perceives sensibles of different senses. For it is, as already stated, more conceivable that it should perceive a
plurality of the former together in this way than a plurality of heterogeneous objects.

If then, as is the fact, the Soul with one part perceives Sweet, with another, White, either that which results
from these is some one part, or else there is no such one resultant. But there must be such an one, inasmuch as
the general faculty of sense-perception is one. What one object, then, does that one faculty [when perceiving
an object, e.g. as both White and Sweet] perceive? [None]; for assuredly no one object arises by composition
of these [heterogeneous objects, such as White and Sweet]. We must conclude, therefore, that there is, as has
been stated before, some one faculty in the soul with which the latter perceives all its percepts, though it
perceives each different genus of sensibles through a different organ.

May we not, then, conceive this faculty which perceives White and Sweet to be one qua indivisible [sc. qua
combining its different simultaneous objects] in its actualization, but different, when it has become divisible
[sc. qua distinguishing its different simultaneous objects] in its actualization?

Or is what occurs in the case of the perceiving Soul conceivably analogous to what holds true in that of the
things themselves? For the same numerically one thing is white and sweet, and has many other qualities,
[while its numerical oneness is not thereby prejudiced] if the fact is not that the qualities are really separable
in the object from one another, but that the being of each quality is different [from that of every other]. In the
same way therefore we must assume also, in the case of the Soul, that the faculty of perception in general is
in itself numerically one and the same, but different [differentiated] in its being; different, that is to say, in
genus as regards some of its objects, in species as regards others. Hence too, we may conclude that one can
perceive [numerically different objects] coinstantaneously with a faculty which is numerically one and the
same, but not the same in its relationship [sc. according as the objects to which it is directed are not the
same].

That every sensible object is a magnitude, and that nothing which it is possible to perceive is indivisible, may
be thus shown. The distance whence an object could not be seen is indeterminate, but that whence it is visible
is determinate. We may say the same of the objects of Smelling and Hearing, and of all sensibles not
discerned by actual contact. Now, there is, in the interval of distance, some extreme place, the last from
which the object is invisible, and the first from which it is visible. This place, beyond which if the object be
one cannot perceive it, while if the object be on the hither side one must perceive it, is, I presume, itself
necessarily indivisible. Therefore, if any sensible object be indivisible, such object, if set in the said extreme
place whence imperceptibility ends and perceptibility begins, will have to be both visible and invisible their
objects, whether regarded in general or at the same time; but this is impossible.

This concludes our survey of the characteristics of the organs of Sense-perception and their objects, whether
regarded in general or in relation to each organ. Of the remaining subjects, we must first consider that of
memory and remembering.

-THE END-

ON THE PARTS OF ANIMALS

by Aristotle

ON THE PARTS OF ANIMALS

Table of Contents

ON THE PARTS OF ANIMALS 1

by Aristotle 1

Book 1 2

_1 2

2 7

_3 7

A 9

_5 10

Book II . 11

_1 11

2 13

3. 16

A 17

5. 18

_6 18

1_ 19

_8 21

_9 22

A0 24

11 25

Al 25

13 26

U 27

15 27

16 28

Al 29

Book III 31

1 31

2 32

1 34

A 36

1 39

6 40

2 41

_8 43

_9 43

10 45

11 46

12 46

13 47

14 47

15 49

Book IV 49

1 50

2 50

1 51

A 52

5 52

ON THE PARTS OF ANIMALS

Table of Contents

_6 57

1 59

_8 59

_9 60

20 62

_H 67

Y2 69

Y3 72

14 74

ON THE PARTS OF ANIMALS

by Aristotle

translated by William Ogle

« Book I
1
2
3
4
5

« Book II

12
11
14
15
16

12
« Book III

12
11

ON THE PARTS OF ANIMALS

•15
« Book IV
1

12
12
14

Book I

EVERY systematic science, the humblest and the noblest alike, seems to admit of two distinct kinds of
proficiency; one of which may be properly called scientific knowledge of the subject, while the other is a
kind of educational acquaintance with it. For an educated man should be able to form a fair off-hand
judgement as to the goodness or badness of the method used by a professor in his exposition. To be educated
is in fact to be able to do this; and even the man of universal education we deem to be such in virtue of his
having this ability. It will, however, of course, be understood that we only ascribe universal education to one
who in his own individual person is thus critical in all or nearly all branches of knowledge, and not to one
who has a like ability merely in some special subject. For it is possible for a man to have this competence in
some one branch of knowledge without having it in all.

It is plain then that, as in other sciences, so in that which inquires into nature, there must be certain canons, by
reference to which a hearer shall be able to criticize the method of a professed exposition, quite
independently of the question whether the statements made be true or false. Ought we, for instance (to give
an illustration of what I mean), to begin by discussing each separate species-man, lion, ox, and the
like-taking each kind in hand inde. pendently of the rest, or ought we rather to deal first with the attributes
which they have in common in virtue of some common element of their nature, and proceed from this as a
basis for the consideration of them separately? For genera that are quite distinct yet oftentimes present many
identical phenomena, sleep, for instance, respiration, growth, decay, death, and other similar affections and
conditions, which may be passed over for the present, as we are not yet prepared to treat of them with
clearness and precision. Now it is plain that if we deal with each species independently of the rest, we shall
frequently be obliged to repeat the same statements over and over again; for horse and dog and man present,
each and all, every one of the phenomena just enumerated. A discussion therefore of the attributes of each
such species separately would necessarily involve frequent repetitions as to characters, themselves identical
but recurring in animals specifically distinct. (Very possibly also there may be other characters which, though
they present specific differences, yet come under one and the same category. For instance, flying, swimming,
walking, creeping, are plainly specifically distinct, but yet are all forms of animal progression.) We must,
then, have some clear understanding as to the manner in which our investigation is to be conducted; whether,

Book I 2

ON THE PARTS OF ANIMALS

I mean, we are first to deal with the common or generic characters, and afterwards to take into consideration
special peculiarities; or whether we are to start straight off with the ultimate species. For as yet no definite
rule has been laid down in this matter. So also there is a like uncertainty as to another point now to be
mentioned. Ought the writer who deals with the works of nature to follow the plan adopted by the
mathematicians in their astronomical demonstrations, and after considering the phenomena presented by
animals, and their several parts, proceed subsequently to treat of the causes and the reason why; or ought he
to follow some other method? And when these questions are answered, there yet remains another. The causes
concerned in the generation of the works of nature are, as we see, more than one. There is the final cause and
there is the motor cause. Now we must decide which of these two causes comes first, which second. Plainly,
however, that cause is the first which we call the final one. For this is the Reason, and the Reason forms the
starting-point, alike in the works of art and in works of nature. For consider how the physician or how the
builder sets about his work. He starts by forming for himself a definite picture, in the one case perceptible to
mind, in the other to sense, of his end-the physician of health, the builder of a house-and this he holds
forward as the reason and explanation of each subsequent step that he takes, and of his acting in this or that
way as the case may be. Now in the works of nature the good end and the final cause is still more dominant
than in works of art such as these, nor is necessity a factor with the same significance in them all; though
almost all writers, while they try to refer their origin to this cause, do so without distinguishing the various
senses in which the term necessity is used. For there is absolute necessity, manifested in eternal phenomena;
and there is hypothetical necessity, manifested in everything that is generated by nature as in everything that
is produced by art, be it a house or what it may. For if a house or other such final object is to be realized, it is
necessary that such and such material shall exist; and it is necessary that first this then that shall be produced,
and first this and then that set in motion, and so on in continuous succession, until the end and final result is
reached, for the sake of which each prior thing is produced and exists. As with these productions of art, so
also is it with the productions of nature. The mode of necessity, however, and the mode of ratiocination are
different in natural science from what they are in the theoretical sciences; of which we have spoken
elsewhere. For in the latter the starting-point is that which is; in the former that which is to be. For it is that
which is yet to be-health, let us say, or a man-that, owing to its being of such and such characters,
necessitates the pre-existence or previous production of this and that antecedent; and not this or that
antecedent which, because it exists or has been generated, makes it necessary that health or a man is in, or
shall come into, existence. Nor is it possible to track back the series of necessary antecedents to a
starting-point, of which you can say that, existing itself from eternity, it has determined their existence as its
consequent. These however again, are matters that have been dealt with in another treatise. There too it was
stated in what cases absolute and hypothetical necessity exist; in what cases also the proposition expressing
hypothetical necessity is simply convertible, and what cause it is that determines this convertibility.

Another matter which must not be passed over without consideration is, whether the proper subject of our
exposition is that with which the ancient writers concerned themselves, namely, what is the process of
formation of each animal; or whether it is not rather, what are the characters of a given creature when formed.
For there is no small difference between these two views. The best course appears to be that we should follow
the method already mentioned, and begin with the phenomena presented by each group of animals, and, when
this is done, proceed afterwards to state the causes of those phenomena, and to deal with their evolution. For
elsewhere, as for instance in house building, this is the true sequence. The plan of the house, or the house, has
this and that form; and because it has this and that form, therefore is its construction carried out in this or that
manner. For the process of evolution is for the sake of the thing Anally evolved, and not this for the sake of
the process. Empedocles, then, was in error when he said that many of the characters presented by animals
were merely the results of incidental occurrences during their development; for instance, that the backbone
was divided as it is into vertebrae, because it happened to be broken owing to the contorted position of the
foetus in the womb. In so saying he overlooked the fact that propagation implies a creative seed endowed
with certain formative properties. Secondly, he neglected another fact, namely, that the parent animal
pre-exists, not only in idea, but actually in time. For man is generated from man; and thus it is the possession
of certain characters by the parent that determines the development of like characters in the child. The same

Book I 3

ON THE PARTS OF ANIMALS

statement holds good also for the operations of art, and even for those which are apparently spontaneous. For
the same result as is produced by art may occur spontaneously. Spontaneity, for instance, may bring about the
restoration of health. The products of art, however, require the pre-existence of an efficient cause
homogeneous with themselves, such as the statuary's art, which must necessarily precede the statue; for this
cannot possibly be produced spontaneously. Art indeed consists in the conception of the result to be produced
before its realization in the material. As with spontaneity, so with chance; for this also produces the same
result as art, and by the same process.

The fittest mode, then, of treatment is to say, a man has such and such parts, because the conception of a man
includes their presence, and because they are necessary conditions of his existence, or, if we cannot quite say
this, which would be best of all, then the next thing to it, namely, that it is either quite impossible for him to
exist without them, or, at any rate, that it is better for him that they should be there; and their existence
involves the existence of other antecedents. Thus we should say, because man is an animal with such and
such characters, therefore is the process of his development necessarily such as it is; and therefore is it
accomplished in such and such an order, this part being formed first, that next, and so on in succession; and
after a like fashion should we explain the evolution of all other works of nature.

Now that with which the ancient writers, who first philosophized about Nature, busied themselves, was the
material principle and the material cause. They inquired what this is, and what its character; how the universe
is generated out of it, and by what motor influence, whether, for instance, by antagonism or friendship,
whether by intelligence or spontaneous action, the substratum of matter being assumed to have certain
inseparable properties; fire, for instance, to have a hot nature, earth a cold one; the former to be light, the
latter heavy. For even the genesis of the universe is thus explained by them. After a like fashion do they deal
also with the development of plants and of animals. They say, for instance, that the water contained in the
body causes by its currents the formation of the stomach and the other receptacles of food or of excretion; and
that the breath by its passage breaks open the outlets of the nostrils; air and water being the materials of
which bodies are made; for all represent nature as composed of such or similar substances.

But if men and animals and their several parts are natural phenomena, then the natural philosopher must take
into consideration not merely the ultimate substances of which they are made, but also flesh, bone, blood, and
all other homogeneous parts; not only these, but also the heterogeneous parts, such as face, hand, foot; and
must examine how each of these comes to be what it is, and in virtue of what force. For to say what are the
ultimate substances out of which an animal is formed, to state, for instance, that it is made of fire or earth, is
no more sufficient than would be a similar account in the case of a couch or the like. For we should not be
content with saying that the couch was made of bronze or wood or whatever it might be, but should try to
describe its design or mode of composition in preference to the material; or, if we did deal with the material,
it would at any rate be with the concretion of material and form. For a couch is such and such a form
embodied in this or that matter, or such and such a matter with this or that form; so that its shape and
structure must be included in our description. For the formal nature is of greater importance than the material
nature.

Does, then, configuration and colour constitute the essence of the various animals and of their several parts?
For if so, what Democritus says will be strictly correct. For such appears to have been his notion. At any rate
he says that it is evident to every one what form it is that makes the man, seeing that he is recognizable by his
shape and colour. And yet a dead body has exactly the same configuration as a living one; but for all that is
not a man. So also no hand of bronze or wood or constituted in any but the appropriate way can possibly be a
hand in more than name. For like a physician in a painting, or like a flute in a sculpture, in spite of its name it
will be unable to do the office which that name implies. Precisely in the same way no part of a dead body,
such I mean as its eye or its hand, is really an eye or a hand. To say, then, that shape and colour constitute the
animal is an inadequate statement, and is much the same as if a woodcarver were to insist that the hand he
had cut out was really a hand. Yet the physiologists, when they give an account of the development and

Book I 4

ON THE PARTS OF ANIMALS

causes of the animal form, speak very much like such a craftsman. What, however, I would ask, are the forces
by which the hand or the body was fashioned into its shape? The woodcarver will perhaps say, by the axe or
the auger; the physiologist, by air and by earth. Of these two answers the artificer's is the better, but it is
nevertheless insufficient. For it is not enough for him to say that by the stroke of his tool this part was formed
into a concavity, that into a flat surface; but he must state the reasons why he struck his blow in such a way as
to effect this, and what his final object was; namely, that the piece of wood should develop eventually into
this or that shape. It is plain, then, that the teaching of the old physiologists is inadequate, and that the true
method is to state what the definitive characters are that distinguish the animal as a whole; to explain what it
is both in substance and in form, and to deal after the same fashion with its several organs; in fact, to proceed
in exactly the same way as we should do, were we giving a complete description of a couch.

If now this something that constitutes the form of the living being be the soul, or part of the soul, or
something that without the soul cannot exist; as would seem to be the case, seeing at any rate that when the
soul departs, what is left is no longer a living animal, and that none of the parts remain what they were
before, excepting in mere configuration, like the animals that in the fable are turned into stone; if, I say, this
be so, then it will come within the province of the natural philosopher to inform himself concerning the soul,
and to treat of it, either in its entirety, or, at any rate, of that part of it which constitutes the essential character
of an animal; and it will be his duty to say what this soul or this part of a soul is; and to discuss the attributes
that attach to this essential character, especially as nature is spoken of in two senses, and the nature of a thing
is either its matter or its essence; nature as essence including both the motor cause and the final cause. Now it
is in the latter of these two senses that either the whole soul or some part of it constitutes the nature of an
animal; and inasmuch as it is the presence of the soul that enables matter to constitute the animal nature,
much more than it is the presence of matter which so enables the soul, the inquirer into nature is bound on
every ground to treat of the soul rather than of the matter. For though the wood of which they are made
constitutes the couch and the tripod, it only does so because it is capable of receiving such and such a form.

What has been said suggests the question, whether it is the whole soul or only some part of it, the
consideration of which comes within the province of natural science. Now if it be of the whole soul that this
should treat, then there is no place for any other philosophy beside it. For as it belongs in all cases to one and
the same science to deal with correlated subjects-one and the same science, for instance, deals with sensation
and with the objects of sense-and as therefore the intelligent soul and the objects of intellect, being
correlated, must belong to one and the same science, it follows that natural science will have to include the
whole universe in its province. But perhaps it is not the whole soul, nor all its parts collectively, that
constitutes the source of motion; but there may be one part, identical with that in plants, which is the source
of growth, another, namely the sensory part, which is the source of change of quality, while still another, and
this not the intellectual part, is the source of locomotion. I say not the intellectual part; for other animals than
man have the power of locomotion, but in none but him is there intellect. Thus then it is plain that it is not of
the whole soul that we have to treat. For it is not the whole soul that constitutes the animal nature, but only
some part or parts of it. Moreover, it is impossible that any abstraction can form a subject of natural science,
seeing that everything that Nature makes is means to an end. For just as human creations are the products of
art, so living objects are manifest in the products of an analogous cause or principle, not external but internal,
derived like the hot and the cold from the environing universe. And that the heaven, if it had an origin, was
evolved and is maintained by such a cause, there is therefore even more reason to believe, than that mortal
animals so originated. For order and definiteness are much more plainly manifest in the celestial bodies than
in our own frame; while change and chance are characteristic of the perishable things of earth. Yet there are
some who, while they allow that every animal exists and was generated by nature, nevertheless hold that the
heaven was constructed to be what it is by chance and spontaneity; the heaven, in which not the faintest sign
of haphazard or of disorder is discernible! Again, whenever there is plainly some final end, to which a motion
tends should nothing stand in the way, we always say that such final end is the aim or purpose of the motion;
and from this it is evident that there must be a something or other really existing, corresponding to what we
call by the name of Nature. For a given germ does not give rise to any chance living being, nor spring from

Book I 5

ON THE PARTS OF ANIMALS

any chance one; but each germ springs from a definite parent and gives rise to a definite progeny. And thus it
is the germ that is the ruling influence and fabricator of the offspring. For these it is by nature, the offspring
being at any rate that which in nature will spring from it. At the same time the offspring is anterior to the
germ; for germ and perfected progeny are related as the developmental process and the result. Anterior,
however, to both germ and product is the organism from which the germ was derived. For every germ implies
two organisms, the parent and the progeny. For germ or seed is both the seed of the organism from which it
came, of the horse, for instance, from which it was derived, and the seed of the organism that will eventually
arise from it, of the mule, for example, which is developed from the seed of the horse. The same seed then is
the seed both of the horse and of the mule, though in different ways as here set forth. Moreover, the seed is
potentially that which will spring from it, and the relation of potentiality to actuality we know.

There are then two causes, namely, necessity and the final end. For many things are produced, simply as the
results of necessity. It may, however, be asked, of what mode of necessity are we speaking when we say this.
For it can be of neither of those two modes which are set forth in the philosophical treatises. There is,
however, the third mode, in such things at any rate as are generated. For instance, we say that food is
necessary; because an animal cannot possibly do without it. This third mode is what may be called
hypothetical necessity. Here is another example of it. If a piece of wood is to be split with an axe, the axe
must of necessity be hard; and, if hard, must of necessity be made of bronze or iron. Now exactly in the same
way the body, which like the axe is an instrument-for both the body as a whole and its several parts
individually have definite operations for which they are made-just in the same way, I say, the body, if it is to
do its work, must of necessity be of such and such a character, and made of such and such materials.

It is plain then that there are two modes of causation, and that both of these must, so far as possible, be taken
into account in explaining the works of nature, or that at any rate an attempt must be made to include them
both; and that those who fail in this tell us in reality nothing about nature. For primary cause constitutes the
nature of an animal much more than does its matter. There are indeed passages in which even Empedocles
hits upon this, and following the guidance of fact, finds himself constrained to speak of the ratio (olugos) as
constituting the essence and real nature of things. Such, for instance, is the case when he explains what is a
bone. For he does not merely describe its material, and say it is this one element, or those two or three
elements, or a compound of all the elements, but states the ratio (olugos) of their combination. As with a
bone, so manifestly is it with the flesh and all other similar parts.

The reason why our predecessors failed in hitting upon this method of treatment was, that they were not in
possession of the notion of essence, nor of any definition of substance. The first who came near it was
Democritus, and he was far from adopting it as a necessary method in natural science, but was merely
brought to it, spite of himself, by constraint of facts. In the time of Socrates a nearer approach was made to
the method. But at this period men gave up inquiring into the works of nature, and philosophers diverted their
attention to political science and to the virtues which benefit mankind.

Of the method itself the following is an example. In dealing with respiration we must show that it takes place
for such or such a final object; and we must also show that this and that part of the process is necessitated by
this and that other stage of it. By necessity we shall sometimes mean hypothetical necessity, the necessity,
that is, that the requisite antecedants shall be there, if the final end is to be reached; and sometimes absolute
necessity, such necessity as that which connects substances and their inherent properties and characters. For
the alternate discharge and re-entrance of heat and the inflow of air are necessary if we are to live. Here we
have at once a necessity in the former of the two senses. But the alternation of heat and refrigeration produces
of necessity an alternate admission and discharge of the outer air, and this is a necessity of the second kind.

In the foregoing we have an example of the method which we must adopt, and also an example of the kind of
phenomena, the causes of which we have to investigate.

Book I

ON THE PARTS OF ANIMALS

Some writers propose to reach the definitions of the ultimate forms of animal life by bipartite division. But
this method is often difficult, and often impracticable.

Sometimes the final differentia of the subdivision is sufficient by itself, and the antecedent differentiae are
mere surplusage. Thus in the series Footed, Two-footed, Cleft-footed, the last term is all-expressive by
itself, and to append the higher terms is only an idle iteration. Again it is not permissible to break up a natural
group, Birds for instance, by putting its members under different bifurcations, as is done in the published
dichotomies, where some birds are ranked with animals of the water, and others placed in a different class.
The group Birds and the group Fishes happen to be named, while other natural groups have no popular
names; for instance, the groups that we may call Sanguineous and Bloodless are not known popularly by any
designations. If such natural groups are not to be broken up, the method of Dichotomy cannot be employed,
for it necessarily involves such breaking up and dislocation. The group of the Many-footed, for instance,
would, under this method, have to be dismembered, and some of its kinds distributed among land animals,
others among water animals.

Again, privative terms inevitably form one branch of dichotomous division, as we see in the proposed
dichotomies. But privative terms in their character of privatives admit of no subdivision. For there can be no
specific forms of a negation, of Featherless for instance or of Footless, as there are of Feathered and of
Footed. Yet a generic differentia must be subdivisible; for otherwise what is there that makes it generic rather
than specific? There are to be found generic, that is specifically subdivisible, differentiae; Feathered for
instance and Footed. For feathers are divisible into Barbed and Unbarbed, and feet into Manycleft, and
Twocleft, like those of animals with bifid hoofs, and Uncleft or Undivided, like those of animals with solid
hoofs. Now even with differentiae capable of this specific subdivision it is difficult enough so to make the
classification, as that each animal shall be comprehended in some one subdivision and in not more than one;
but far more difficult, nay impossible, is it to do this, if we start with a dichotomy into two contradictories.
(Suppose for instance we start with the two contradictories, Feathered and Unfeathered; we shall find that the
ant, the glow-worm, and some other animals fall under both divisions.) For each differentia must be
presented by some species. There must be some species, therefore, under the privative heading. Now
specifically distinct animals cannot present in their essence a common undifferentiated element, but any
apparently common element must really be differentiated. (Bird and Man for instance are both Two-footed,
but their two-footedness is diverse and differentiated. So any two sanguineous groups must have some
difference in their blood, if their blood is part of their essence.) From this it follows that a privative term,
being insusceptible of differentiation, cannot be a generic differentia; for, if it were, there would be a
common undifferentiated element in two different groups.

Again, if the species are ultimate indivisible groups, that is, are groups with indivisible differentiae, and if no
differentia be common to several groups, the number of differentiae must be equal to the number of species.
If a differentia though not divisible could yet be common to several groups, then it is plain that in virtue of
that common differentia specifically distinct animals would fall into the same division. It is necessary then, if
the differentiae, under which are ranged all the ultimate and indivisible groups, are specific characters, that
none of them shall be common; for otherwise, as already said, specifically distinct animals will come into one
and the same division. But this would violate one of the requisite conditions, which are as follows. No
ultimate group must be included in more than a single division; different groups must not be included in the
same division; and every group must be found in some division. It is plain then that we cannot get at the
ultimate specific forms of the animal, or any other, kingdom by bifurcate division. If we could, the number of
ultimate differentiae would equal the number of ultimate animal forms. For assume an order of beings whose

ON THE PARTS OF ANIMALS

prime differentiae are White and Black. Each of these branches will bifurcate, and their branches again, and
so on till we reach the ultimate differentiae, whose number will be four or some other power of two, and will
also be the number of the ultimate species comprehended in the order.

(A species is constituted by the combination differentia and matter. For no part of an animal is purely
material or purely immaterial; nor can a body, independently of its condition, constitute an animal or any of
its parts, as has repeatedly been observed.)

Further, the differentiae must be elements of the essence, and not merely essential attributes. Thus if Figure is
the term to be divided, it must not be divided into figures whose angles are equal to two right angles, and
figures whose angles are together greater than two right angles. For it is only an attribute of a triangle and not
part of its essence that its angles are equal to two right angles.

Again, the bifurcations must be opposites, like White and Black, Straight and Bent; and if we characterize
one branch by either term, we must characterize the other by its opposite, and not, for example, characterize
one branch by a colour, the other by a mode of progression, swimming for instance.

Furthermore, living beings cannot be divided by the functions common to body and soul, by Flying, for
instance, and Walking, as we see them divided in the dichotomies already referred to. For some groups, Ants
for instance, fall under both divisions, some ants flying while others do not. Similarly as regards the division
into Wild and Tame; for it also would involve the disruption of a species into different groups. For in almost
all species in which some members are tame, there are other members that are wild. Such, for example, is the
case with Men, Horses, Oxen, Dogs in India, Pigs, Goats, Sheep; groups which, if double, ought to have what
they have not, namely, different appellations; and which, if single, prove that Wildness and Tameness do not
amount to specific differences. And whatever single element we take as a basis of division the same difficulty
will occur.

The method then that we must adopt is to attempt to recognize the natural groups, following the indications
afforded by the instincts of mankind, which led them for instance to form the class of Birds and the class of
Fishes, each of which groups combines a multitude of differentiae, and is not defined by a single one as in
dichotomy. The method of dichotomy is either impossible (for it would put a single group under different
divisions or contrary groups under the same division), or it only furnishes a single ultimate differentia for
each species, which either alone or with its series of antecedents has to constitute the ultimate species.

If, again, a new differential character be introduced at any stage into the division, the necessary result is that
the continuity of the division becomes merely a unity and continuity of agglomeration, like the unity and
continuity of a series of sentences coupled together by conjunctive particles. For instance, suppose we have
the bifurcation Feathered and Featherless, and then divide Feathered into Wild and Tame, or into White and
Black. Tame and White are not a differentiation of Feathered, but are the commencement of an independent
bifurcation, and are foreign to the series at the end of which they are introduced.

As we said then, we must define at the outset by multiplicity of differentiae. If we do so, privative terms will
be available, which are unavailable to the dichotomist.

The impossibility of reaching the definition of any of the ultimate forms by dichotomy of the larger group, as
some propose, is manifest also from the following considerations. It is impossible that a single differentia,
either by itself or with its antecedents, shall express the whole essence of a species. (In saying a single
differentia by itself I mean such an isolated differentia as Cleft-footed; in saying a single differentia with
antecedent I mean, to give an instance, Manycleft-footed preceded by Cleft-footed. The very continuity of a
series of successive differentiae in a division is intended to show that it is their combination that expresses the
character of the resulting unit, or ultimate group. But one is misled by the usages of language into imagining

2 8

ON THE PARTS OF ANIMALS

that it is merely the final term of the series, Manycleft-footed for instance, that constitutes the whole
differentia, and that the antecedent terms, Footed, Cleft-footed, are superfluous. Now it is evident that such a
series cannot consist of many terms. For if one divides and subdivides, one soon reaches the final differential
term, but for all that will not have got to the ultimate division, that is, to the species.) No single differentia, I
repeat, either by itself or with its antecedents, can possibly express the essence of a species. Suppose, for
example, Man to be the animal to be defined; the single differentia will be Cleft-footed, either by itself or
with its antecedents, Footed and Two-footed. Now if man was nothing more than a Cleft-footed animal, this
single differentia would duly represent his essence. But seeing that this is not the case, more differentiae than
this one will necessarily be required to define him; and these cannot come under one division; for each single
branch of a dichotomy ends in a single differentia, and cannot possibly include several differentiae belonging
to one and the same animal.

It is impossible then to reach any of the ultimate animal forms by dichotomous division.

It deserves inquiry why a single name denoting a higher group was not invented by mankind, as an
appellation to comprehend the two groups of Water animals and Winged animals. For even these have certain
attributes in common. However, the present nomenclature is just. Groups that only differ in degree, and in the
more or less of an identical element that they possess, are aggregated under a single class; groups whose
attributes are not identical but analogous are separated. For instance, bird differs from bird by gradation, or
by excess and defect; some birds have long feathers, others short ones, but all are feathered. Bird and Fish are
more remote and only agree in having analogous organs; for what in the bird is feather, in the fish is scale.
Such analogies can scarcely, however, serve universally as indications for the formation of groups, for almost
all animals present analogies in their corresponding parts.

The individuals comprised within a species, such as Socrates and Coriscus, are the real existences; but
inasmuch as these individuals possess one common specific form, it will suffice to state the universal
attributes of the species, that is, the attributes common to all its individuals, once for all, as otherwise there
will be endless reiteration, as has already been pointed out.

But as regards the larger groups-such as Birds-which comprehend many species, there may be a question.
For on the one hand it may be urged that as the ultimate species represent the real existences, it will be well,
if practicable, to examine these ultimate species separately, just as we examine the species Man separately; to
examine, that is, not the whole class Birds collectively, but the Ostrich, the Crane, and the other indivisible
groups or species belonging to the class.

On the other hand, however, this course would involve repeated mention of the same attribute, as the same
attribute is common to many species, and so far would be somewhat irrational and tedious. Perhaps, then, it
will be best to treat generically the universal attributes of the groups that have a common nature and contain
closely allied subordinate forms, whether they are groups recognized by a true instinct of mankind, such as
Birds and Fishes, or groups not popularly known by a common appellation, but withal composed of closely
allied subordinate groups; and only to deal individually with the attributes of a single species, when such
species, man, for instance, and any other such, if such there be-stands apart from others, and does not
constitute with them a larger natural group.

It is generally similarity in the shape of particular organs, or of the whole body, that has determined the
formation of the larger groups. It is in virtue of such a similarity that Birds, Fishes, Cephalopoda, and
Testacea have been made to form each a separate class. For within the limits of each such class, the parts do
not differ in that they have no nearer resemblance than that of analogy-such as exists between the bone of

ON THE PARTS OF ANIMALS

man and the spine of fish-but differ merely in respect of such corporeal conditions as largeness smallness,
softness hardness, smoothness roughness, and other similar oppositions, or, in one word, in respect of degree.

We have now touched upon the canons for criticizing the method of natural science, and have considered
what is the most systematic and easy course of investigation; we have also dealt with division, and the mode
of conducting it so as best to attain the ends of science, and have shown why dichotomy is either
impracticable or inefficacious for its professed purposes.

Having laid this foundation, let us pass on to our next topic.

Of things constituted by nature some are ungenerated, imperishable, and eternal, while others are subject to
generation and decay. The former are excellent beyond compare and divine, but less accessible to knowledge.
The evidence that might throw light on them, and on the problems which we long to solve respecting them, is
furnished but scantily by sensation; whereas respecting perishable plants and animals we have abundant
information, living as we do in their midst, and ample data may be collected concerning all their various
kinds, if only we are willing to take sufficient pains. Both departments, however, have their special charm.
The scanty conceptions to which we can attain of celestial things give us, from their excellence, more
pleasure than all our knowledge of the world in which we live; just as a half glimpse of persons that we love
is more delightful than a leisurely view of other things, whatever their number and dimensions. On the other
hand, in certitude and in completeness our knowledge of terrestrial things has the advantage. Moreover, their
greater nearness and affinity to us balances somewhat the loftier interest of the heavenly things that are the
objects of the higher philosophy. Having already treated of the celestial world, as far as our conjectures could
reach, we proceed to treat of animals, without omitting, to the best of our ability, any member of the
kingdom, however ignoble. For if some have no graces to charm the sense, yet even these, by disclosing to
intellectual perception the artistic spirit that designed them, give immense pleasure to all who can trace links
of causation, and are inclined to philosophy. Indeed, it would be strange if mimic representations of them
were attractive, because they disclose the mimetic skill of the painter or sculptor, and the original realities
themselves were not more interesting, to all at any rate who have eyes to discern the reasons that determined
their formation. We therefore must not recoil with childish aversion from the examination of the humbler
animals. Every realm of nature is marvellous: and as Heraclitus, when the strangers who came to visit him
found him warming himself at the furnace in the kitchen and hesitated to go in, reported to have bidden them
not to be afraid to enter, as even in that kitchen divinities were present, so we should venture on the study of
every kind of animal without distaste; for each and all will reveal to us something natural and something
beautiful. Absence of haphazard and conduciveness of everything to an end are to be found in Nature's works
in the highest degree, and the resultant end of her generations and combinations is a form of the beautiful.

If any person thinks the examination of the rest of the animal kingdom an unworthy task, he must hold in like
disesteem the study of man. For no one can look at the primordia of the human frame-blood, flesh, bones,
vessels, and the like-without much repugnance. Moreover, when any one of the parts or structures, be it
which it may, is under discussion, it must not be supposed that it is its material composition to which
attention is being directed or which is the object of the discussion, but the relation of such part to the total
form. Similarly, the true object of architecture is not bricks, mortar, or timber, but the house; and so the
principal object of natural philosophy is not the material elements, but their composition, and the totality of
the form, independently of which they have no existence.

The course of exposition must be first to state the attributes common to whole groups of animals, and then to
attempt to give their explanation. Many groups, as already noticed, present common attributes, that is to say,
in some cases absolutely identical affections, and absolutely identical organs,-feet, feathers, scales, and the

5 10

ON THE PARTS OF ANIMALS

like-while in other groups the affections and organs are only so far identical as that they are analogous. For
instance, some groups have lungs, others have no lung, but an organ analogous to a lung in its place; some
have blood, others have no blood, but a fluid analogous to blood, and with the same office. To treat of the
common attributes in connexion with each individual group would involve, as already suggested, useless
iteration. For many groups have common attributes. So much for this topic.

As every instrument and every bodily member subserves some partial end, that is to say, some special action,
so the whole body must be destined to minister to some Plenary sphere of action. Thus the saw is made for
sawing, for sawing is a function, and not sawing for the saw. Similarly, the body too must somehow or other
be made for the soul, and each part of it for some subordinate function, to which it is adapted.

We have, then, first to describe the common functions, common, that is, to the whole animal kingdom, or to
certain large groups, or to the members of a species. In other words, we have to describe the attributes
common to all animals, or to assemblages, like the class of Birds, of closely allied groups differentiated by
gradation, or to groups like Man not differentiated into subordinate groups. In the first case the common
attributes may be called analogous, in the second generic, in the third specific.

When a function is ancillary to another, a like relation manifestly obtains between the organs which discharge
these functions; and similarly, if one function is prior to and the end of another, their respective organs will
stand to each other in the same relation. Thirdly, the existence of these parts involves that of other things as
their necessary consequents.

Instances of what I mean by functions and affections are Reproduction, Growth, Copulation, Waking, Sleep,
Locomotion, and other similar vital actions. Instances of what I mean by parts are Nose, Eye, Face, and other
so-called members or limbs, and also the more elementary parts of which these are made. So much for the
method to be pursued. Let us now try to set forth the causes of all vital phenomena, whether universal or
particular, and in so doing let us follow that order of exposition which conforms, as we have indicated, to the
order of nature.

Book II

THE nature and the number of the parts of which animals are severally composed are matters which have
already been set forth in detail in the book of Researches about Animals. We have now to inquire what are
the causes that in each case have determined this composition, a subject quite distinct from that dealt with in
the Researches.

Now there are three degrees of composition; and of these the first in order, as all will allow, is composition
out of what some call the elements, such as earth, air, water, fire. Perhaps, however, it would be more
accurate to say composition out of the elementary forces; nor indeed out of all of these, but out of a limited
number of them, as defined in previous treatises. For fluid and solid, hot and cold, form the material of all
composite bodies; and all other differences are secondary to these, such differences, that is, as heaviness or
lightness, density or rarity, roughness or smoothness, and any other such properties of matter as there may be.
second degree of composition is that by which the homogeneous parts of animals, such as bone, flesh, and the
like, are constituted out of the primary substances. The third and last stage is the composition which forms
the heterogeneous parts, such as face, hand, and the rest.

Now the order of actual development and the order of logical existence are always the inverse of each other.
For that which is posterior in the order of development is antecedent in the order of nature, and that is

Book II 11

ON THE PARTS OF ANIMALS

genetically last which in nature is first.

(That this is so is manifest by induction; for a house does not exist for the sake of bricks and stones, but these
materials for the sake of the house; and the same is the case with the materials of other bodies. Nor is
induction required to show this, it is included in our conception of generation. For generation is a process
from a something to a something; that which is generated having a cause in which it originates and a cause in
which it ends. The originating cause is the primary efficient cause, which is something already endowed with
tangible existence, while the final cause is some definite form or similar end; for man generates man, and
plant generates plant, in each case out of the underlying material.)

In order of time, then, the material and the generative process must necessarily be anterior to the being that is
generated; but in logical order the definitive character and form of each being precedes the material. This is
evident if one only tries to define the process of formation. For the definition of house-building includes and
presupposes that of the house; but the definition of the house does not include nor presuppose that of
house-building; and the same is true of all other productions. So that it must necessarily be that the
elementary material exists for the sake of the homogeneous parts, seeing that these are genetically posterior to
it, just as the heterogeneous parts are posterior genetically to them. For these heterogeneous parts have
reached the end and goal, having the third degree of composition, in which degree generation or development
often attains its final term.

Animals, then, are composed of homogeneous parts, and are also composed of heterogeneous parts. The
former, however, exist for the sake of the latter. For the active functions and operations of the body are
carried on by these; that is, by the heterogeneous parts, such as the eye, the nostril, the whole face, the
fingers, the hand, and the whole arm. But inasmuch as there is a great variety in the functions and motions not
only of aggregate animals but also of the individual organs, it is necessary that the substances out of which
these are composed shall present a diversity of properties. For some purposes softness is advantageous, for
others hardness; some parts must be capable of extension, others of flexion. Such properties, then, are
distributed separately to the different homogeneous parts, one being soft another hard, one fluid another solid,
one viscous another brittle; whereas each of the heterogeneous parts presents a combination of multifarious
properties. For the hand, to take an example, requires one property to enable it to effect pressure, and another
and different property for simple prehension. For this reason the active or executive parts of the body are
compounded out of bones, sinews, flesh, and the like, but not these latter out of the former.

So far, then, as has yet been stated, the relations between these two orders of parts are determined by a final
cause. We have, however, to inquire whether necessity may not also have a share in the matter; and it must be
admitted that these mutual relations could not from the very beginning have possibly been other than they
are. For heterogeneous parts can be made up out of homogeneous parts, either from a plurality of them, or
from a single one, as is the case with some of the viscera which, varying in configuration, are yet, to speak
broadly, formed from a single homogeneous substance; but that homogeneous substances should be formed
out of a combination of heterogeneous parts is clearly an impossibility. For these causes, then, some parts of
animals are simple and homogeneous, while others are composite and heterogeneous; and dividing the parts
into the active or executive and the sensitive, each one of the former is, as before said, heterogeneous, and
each one of the latter homogeneous. For it is in homogeneous parts alone that sensation can occur, as the
following considerations show.

Each sense is confined to a single order of sensibles, and its organ must be such as to admit the action of that
kind or order. But it is only that which is endowed with a property in posse that is acted on by that which has
the like property in esse, so that the two are the same in kind, and if the latter is single so also is the former.
Thus it is that while no physiologists ever dream of saying of the hand or face or other such part that one is
earth, another water, another fire, they couple each separate sense-organ with a separate element, asserting
this one to be air and that other to be fire.

Book II 12

ON THE PARTS OF ANIMALS

Sensation, then, is confined to the simple or homogeneous parts. But, as might reasonably be expected, the
organ of touch, though still homogeneous, is yet the least simple of all the sense-organs. For touch more than
any other sense appears to be correlated to several distinct kinds of objects, and to recognize more than one
category of contrasts, heat and cold, for instance, solidity and fluidity, and other similar oppositions.
Accordingly, the organ which deals with these varied objects is of all the sense-organs the most corporeal,
being either the flesh, or the substance which in some animals takes the place of flesh.

Now as there cannot possibly be an animal without sensation, it follows as a necessary consequence that
every animal must have some homogeneous parts; for these alone are capable of sensation, the heterogeneous
parts serving for the active functions. Again, as the sensory faculty, the motor faculty, and the nutritive
faculty are all lodged in one and the same part of the body, as was stated in a former treatise, it is necessary
that the part which is the primary seat of these principles shall on the one hand, in its character of general
sensory recipient, be one of the simple parts; and on the other hand shall, in its motor and active character, be
one of the heterogeneous parts. For this reason it is the heart which in sanguineous animals constitutes this
central part, and in bloodless animals it is that which takes the place of a heart. For the heart, like the other
viscera, is one of the homogeneous parts; for, if cut up, its pieces are homogeneous in substance with each
other. But it is at the same time heterogeneous in virtue of its definite configuration. And the same is true of
the other so-called viscera, which are indeed formed from the same material as the heart. For all these viscera
have a sanguineous character owing to their being situated upon vascular ducts and branches. For just as a
stream of water deposits mud, so the various viscera, the heart excepted, are, as it were, deposits from the
stream of blood in the vessels. And as to the heart, the very starting-point of the vessels, and the actual seat
of the force by which the blood is first fabricated, it is but what one would naturally expect, that out of the
selfsame nutriment of which it is the recipient its own proper substance shall be formed. Such, then, are the
reasons why the viscera are of sanguineous aspect; and why in one point of view they are homogeneous, in
another heterogeneous.

Of the homogeneous parts of animals, some are soft and fluid, others hard and solid; and of the former some
are fluid permanently, others only so long as they are in the living body. Such are blood, serum, lard, suet,
marrow, semen, bile, milk when present, flesh, and their various analogues. For the parts enumerated are not
to be found in all animals, some animals only having parts analogous to them. Of the hard and solid
homogeneous parts bone, fish-spine, sinew, blood-vessel, are examples. The last of these points to a
sub-division that may be made in the class of homogeneous parts. For in some of them the whole and a
portion of the whole in one sense are designated by the same term-as, for example, is the case with
blood-vessel and bit of blood-vessel-while in another sense they are not; but a portion of a heterogeneous
part, such as face, in no sense has the same designation as the whole.

The first question to be asked is what are the causes to which these homogeneous parts owe their existence?
The causes are various; and this whether the parts be solid or fluid. Thus one set of homogeneous parts
represent the material out of which the heterogeneous parts are formed; for each separate organ is constructed
of bones, sinews, flesh, and the like; which are either essential elements in its formation, or contribute to the
proper discharge of its function. A second set are the nutriment of the first, and are invariably fluid, for all
growth occurs at the expense of fluid matter; while a third set are the residue of the second. Such, for
instance, are the faeces and, in animals that have a bladder, the urine; the former being the dregs of the solid
nutriment, the latter of the fluid.

Even the individual homogeneous parts present variations, which are intended in each case to render them
more serviceable for their purpose. The variations of the blood may be selected to illustrate this. For different
bloods differ in their degrees of thinness or thickness, of clearness or turbidity, of coldness or heat; and this

2 13

ON THE PARTS OF ANIMALS

whether we compare the bloods from different parts of the same individual or the bloods of different animals.
For, in the individual, all the differences just enumerated distinguish the blood of the upper and of the lower
halves of the body; and, dealing with classes, one section of animals is sanguineous, while the other has no
blood, but only something resembling it in its place. As regards the results of such differences, the thicker and
the hotter blood is, the more conducive is it to strength, while in proportion to its thinness and its coldness is
its suitability for sensation and intelligence. A like distinction exists also in the fluid which is analogous to
blood. This explains how it is that bees and other similar creatures are of a more intelligent nature than many
sanguineous animals; and that, of sanguineous animals, those are the most intelligent whose blood is thin and
cold. Noblest of all are those whose blood is hot, and at the same time thin and clear. For such are suited alike
for the development of courage and of intelligence. Accordingly, the upper parts are superior in these respects
to the lower, the male superior to the female, and the right side to the left. As with the blood so also with the
other parts, homogeneous and heterogeneous alike. For here also such variations as occur must be held either
to be related to the essential constitution and mode of life of the several animals, or, in other cases, to be
merely matters of slightly better or slightly worse. Two animals, for instance, may have eyes. But in one
these eyes may be of fluid consistency, while in the other they are hard; and in one there may be eyelids, in
the other no such appendages. In such a case, the fluid consistency and the presence of eyelids, which are
intended to add to the accuracy of vision, are differences of degree. As to why all animals must of necessity
have blood or something of a similar character, and what the nature of blood may be, these are matters which
can only be considered when we have first discussed hot and cold. For the natural properties of many
substances are referable to these two elementary principles; and it is a matter of frequent dispute what
animals or what parts of animals are hot and what cold. For some maintain that water animals are hotter than
such as live on land, asserting that their natural heat counterbalances the coldness of their medium; and again,
that bloodless animals are hotter than those with blood, and females than males. Parmenides, for instance, and
some others declare that women are hotter than men, and that it is the warmth and abundance of their blood
which causes their menstrual flow, while Empedocles maintains the opposite opinion. Again, comparing the
blood and the bile, some speak of the former as hot and of the latter as cold, while others invert the
description. If there be this endless disputing about hot and cold, which of all things that affect our senses are
the most distinct, what are we to think as to our other sensory impressions?

The explanation of the difficulty appears to be that the term 'hotter' is used in several senses; so that different
statements, though in verbal contradiction with each other, may yet all be more or less true. There ought,
then, to be some clear understanding as to the sense in which natural substances are to be termed hot or cold,
solid or fluid. For it appears manifest that these are properties on which even life and death are largely
dependent, and that they are moreover the causes of sleep and waking, of maturity and old age, of health and
disease; while no similar influence belongs to roughness and smoothness, to heaviness and lightness, nor, in
short, to any other such properties of matter. That this should be so is but in accordance with rational
expectation. For hot and cold, solid and fluid, as was stated in a former treatise, are the foundations of the
physical elements.

Is then the term hot used in one sense or in many? To answer this we must ascertain what special effect is
attributed to a hotter substance, and if there be several such, how many these may be. A body then is in one
sense said to be hotter than another, if it impart a greater amount of heat to an object in contact with it. In a
second sense, that is said to be hotter which causes the keener sensation when touched, and especially if the
sensation be attended with pain. This criterion, however, would seem sometimes to be a false one; for
occasionally it is the idiosyncrasy of the individual that causes the sensation to be painful. Again, of two
things, that is the hotter which the more readily melts a fusible substance, or sets on fire an inflammable one.
Again, of two masses of one and the same substance, the larger is said to have more heat than the smaller.
Again, of two bodies, that is said to be the hotter which takes the longer time in cooling, as also we call that
which is rapidly heated hotter than that which is long about it; as though the rapidity implied proximity and
this again similarity of nature, while the want of rapidity implied distance and this again dissimilarity of
nature. The term hotter is used then in all the various senses that have been mentioned, and perhaps in still

2 14

ON THE PARTS OF ANIMALS

more. Now it is impossible for one body to be hotter than another in all these different fashions. Boiling
water for instance, though it is more scalding than flame, yet has no power of burning or melting combustible
or fusible matter, while flame has. So again this boiling water is hotter than a small fire, and yet gets cold
more rapidly and completely. For in fact fire never becomes cold; whereas water invariably does so. Boiling
water, again, is hotter to the touch than oil; yet it gets cold and solid more rapidly than this other fluid. Blood,
again, is hotter to the touch than either water or oil, and yet coagulates before them. Iron, again, and stones
and other similar bodies are longer in getting heated than water, but when once heated burn other substances
with a much greater intensity. Another distinction is this. In some of the bodies which are called hot the heat
is derived from without, while in others it belongs to the bodies themselves; and it makes a most important
difference whether the heat has the former or the latter origin. For to call that one of two bodies the hotter,
which is possessed of heat, we may almost say, accidentally and not of its own essence, is very much the
same thing as if, finding that some man in a fever was a musician, one were to say that musicians are hotter
than healthy men. Of that which is hot per se and that which is hot per accidens, the former is the slower to
cool, while not rarely the latter is the hotter to the touch. The former again is the more burning of the
two-flame, for instance, as compared with boiling water-while the latter, as the boiling water, which is hot
per accidens, is the more heating to the touch. From all this it is clear that it is no simple matter to decide
which of two bodies is the hotter. For the first may be the hotter in one sense, the second the hotter in another.
Indeed in some of these cases it is impossible to say simply even whether a thing is hot or not. For the actual
substratum may not itself be hot, but may be hot when coupled witb heat as an attribute, as would be the case
if one attached a single name to hot water or hot iron. It is after this manner that blood is hot. In such cases, in
those, that is, in which the substratum owes its heat to an external influence, it is plain that cold is not a mere
privation, but an actual existence.

There is no knowing but that even fire may be another of these cases. For the substratum of fire may be
smoke or charcoal, and though the former of these is always hot, smoke being an uprising vapour, yet the
latter becomes cold when its flame is extinguished, as also would oil and pinewood under similar
circumstances. But even substances that have been burnt nearly all possess some heat, cinders, for example,
and ashes, the dejections also of animals, and, among the excretions, bile; because some residue of heat has
been left in them after their combustion. It is in another sense that pinewood and fat substances are hot;
namely, because they rapidly assume the actuality of fire.

Heat appears to cause both coagulation and melting. Now such things as are formed merely of water are
solidified by cold, while such as are formed of nothing but earth are solidified by fire. Hot substances again
are solidified by cold, and, when they consist chiefly of earth, the process of solidification is rapid, and the
resulting substance is insoluble; but, when their main constituent is water, the solid matter is again soluble.
What kinds of substances, however, admit of being solidified, and what are the causes of solidification, are
questions that have already been dealt with more precisely in another treatise.

In conclusion, then, seeing that the terms hot and hotter are used in many different senses, and that no one
substance can be hotter than others in all these senses, we must, when we attribute this character to an object,
add such further statements as that this substance is hotter per se, though that other is often hotter per
accidens; or again, that this substance is potentially hot, that other actually so; or again, that this substance is
hotter in the sense of causing a greater feeling of heat when touched, while that other is hotter in the sense of
producing flame and burning. The term hot being used in all these various senses, it plainly follows that the
term cold will also be used with like ambiguity.

So much then as to the signification of the terms hot and cold, hotter and colder.

ON THE PARTS OF ANIMALS

In natural sequence we have next to treat of solid and fluid. These terms are used in various senses.
Sometimes, for instance, they denote things that are potentially, at other times things that are actually, solid
or fluid. Ice for example, or any other solidified fluid, is spoken of as being actually and accidentally solid,
while potentially and essentially it is fluid. Similarly earth and ashes and the like, when mixed with water, are
actually and accidentally fluid, but potentially and essentially are solid. Now separate the constituents in such
a mixture and you have on the one hand the watery components to which its fluidity was due, and these are
both actually and potentially fluid, and on the other hand the earthy components, and these are in every way
solid; and it is to bodies that are solid in this complete manner that the term 'solid' is most properly and
absolutely applicable. So also the opposite term 'fluid' is strictly and absolutely applicable to that only which
is both potentially and actually fluid. The same remark applies also to hot bodies and to cold.

These distinctions, then, being laid down, it is plain that blood is essentially hot in so far as that heat is
connoted in its name; just as if boiling water were denoted by a single term, boiling would be connoted in
that term. But the substratum of blood, that which it is in substance while it is blood in form, is not hot. Blood
then in a certain sense is essentially hot, and in another sense is not so. For heat is included in the definition
of blood, just as whiteness is included in the definition of a white man, and so far therefore blood is
essentially hot. But so far as blood becomes hot from some external influence, it is not hot essentially.

As with hot and cold, so also is it with solid and fluid. We can therefore understand how some substances are
hot and fluid so long as they remain in the living body, but become perceptibly cold and coagulate so soon as
they are separated from it; while others are hot and consistent while in the body, but when withdrawn under a
change to the opposite condition, and become cold and fluid. Of the former blood is an example, of the latter
bile; for while blood solidifies when thus separated, yellow bile under the same circumstances becomes more
fluid. We must attribute to such substances the possession of opposite properties in a greater or less degree.

In what sense, then, the blood is hot and in what sense fluid, and how far it partakes of the opposite
properties, has now been fairly explained. Now since everything that grows must take nourishment, and
nutriment in all cases consists of fluid and solid substances, and since it is by the force of heat that these are
concocted and changed, it follows that all living things, animals and plants alike, must on this account, if on
no other, have a natural source of heat. This natural heat, moreover, must belong to many parts, seeing that
the organs by which the various elaborations of the food are effected are many in number. For first of all
there is the mouth and the parts inside the mouth, on which the first share in the duty clearly devolves, in
such animals at least as live on food which requires disintegration. The mouth, however, does not actually
concoct the food, but merely facilitates concoction; for the subdivision of the food into small bits facilitates
the action of heat upon it. After the mouth come the upper and the lower abdominal cavities, and here it is
that concoction is effected by the aid of natural heat. Again, just as there is a channel for the admission of the
unconcocted food into the stomach, namely the mouth, and in some animals the so-called oesophagus, which
is continuous with the mouth and reaches to the stomach, so must there also be other and more numerous
channels by which the concocted food or nutriment shall pass out of the stomach and intestines into the body
at large, and to which these cavities shall serve as a kind of manger. For plants get their food from the earth
by means of their roots; and this food is already elaborated when taken in, which is the reason why plants
produce no excrement, the earth and its heat serving them in the stead of a stomach. But animals, with
scarcely an exception, and conspicuously all such as are capable of locomotion, are provided with a
stomachal sac, which is as it were an internal substitute for the earth. They must therefore have some
instrument which shall correspond to the roots of plants, with which they may absorb their food from this sac,
so that the proper end of the successive stages of concoction may at last be attained. The mouth then, its duty
done, passes over the food to the stomach, and there must necessarily be something to receive it in turn from
this. This something is furnished by the bloodvessels, which run throughout the whole extent of the

3 16

ON THE PARTS OF ANIMALS

mesentery from its lowest part right up to the stomach. A description of these will be found in the treatises on
Anatomy and Natural History. Now as there is a receptacle for the entire matter taken as food, and also a
receptacle for its excremental residue, and again a third receptacle, namely the vessels, which serve as such
for the blood, it is plain that this blood must be the final nutritive material in such animals as have it; while in
bloodless animals the same is the case with the fluid which represents the blood. This explains why the blood
diminishes in quantity when no food is taken, and increases when much is consumed, and also why it
becomes healthy and unhealthy according as the food is of the one or the other character. These facts, then,
and others of a like kind, make it plain that the purpose of the blood in sanguineous animals is to subserve the
nutrition of the body. They also explain why no more sensation is produced by touching the blood than by
touching one of the excretions or the food, whereas when the flesh is touched sensation is produced. For the
blood is not continuous nor united by growth with the flesh, but simply lies loose in its receptacle, that is in
the heart and vessels. The manner in which the parts grow at the expense of the blood, and indeed the whole
question of nutrition, will find a more suitable place for exposition in the treatise on Generation, and in other
writings. For our present purpose all that need be said is that the blood exists for the sake of nutrition, that is
the nutrition of the parts; and with this much let us therefore content ourselves.

What are called fibres are found in the blood of some animals but not of all. There are none, for instance, in
the blood of deer and of roes; and for this reason the blood of such animals as these never coagulates. For one
part of the blood consists mainly of water and therefore does not coagulate, this process occurring only in the
other and earthy constituent, that is to say in the fibres, while the fluid part is evaporating.

Some at any rate of the animals with watery blood have a keener intellect than those whose blood is of an
earthier nature. This is due not to the coldness of their blood, but rather to its thinness and purity; neither of
which qualities belongs to the earthy matter. For the thinner and purer its fluid is, the more easily affected is
an animal's sensibility. Thus it is that some bloodless animals, notwithstanding their want of blood, are yet
more intelligent than some among the sanguineous kinds. Such for instance, as already said, is the case with
the bee and the tribe of ants, and whatever other animals there may be of a like nature. At the same time too
great an excess of water makes animals timorous. For fear chills the body; so that in animals whose heart
contains so watery a mixture the way is prepared for the operation of this emotion. For water is congealed by
cold. This also explains why bloodless animals are, as a general rule, more timorous than such as have blood,
so that they remain motionless, when frightened, and discharge their excretions, and in some instances
change colour. Such animals, on the other hand, as have thick and abundant fibres in their blood are of a more
earthy nature, and of a choleric temperament, and liable to bursts of passion. For anger is productive of heat;
and solids, when they have been made hot, give off more heat than fluids. The fibres therefore, being earthy
and solid, are turned into so many hot embers in the blood, like the embers in a vapour-bath, and cause
ebullition in the fits of passion.

This explains why bulls and boars are so choleric and so passionate. For their blood is exceedingly rich in
fibres, and the bull's at any rate coagulates more rapidly than that of any other animal. If these fibres, that is
to say if the earthy constituents of which we are speaking, are taken out of the blood, the fluid that remains
behind will no longer coagulate; just as the watery residue of mud will not coagulate after removal of the
earth. But if the fibres are left the fluid coagulates, as also does mud, under the influence of cold. For when
the heat is expelled by the cold, the fluid, as has been already stated, passes off with it by evaporation, and the
residue is dried up and solidified, not by heat but by cold. So long, however, as the blood is in the body, it is
kept fluid by animal heat.

The character of the blood affects both the temperament and the sensory faculties of animals in many ways.
This is indeed what might reasonably be expected, seeing that the blood is the material of which the whole

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ON THE PARTS OF ANIMALS

body is made. For nutriment supplies the material, and the blood is the ultimate nutriment. It makes then a
considerable difference whether the blood be hot or cold, thin or thick, turbid or clear.

The watery part of the blood is serum; and it is watery, either owing to its not being yet concocted, or owing
to its having become corrupted; so that one part of the serum is the resultant of a necessary process, while
another part is material intended to serve for the formation of the blood.

The differences between lard and suet correspond to differences of blood. For both are blood concocted into
these forms as a result of abundant nutrition, being that surplus blood that is not expended on the fleshy part
of the body, and is of an easily concocted and fatty character. This is shown by the unctuous aspect of these
substances; for such unctuous aspect in fluids is due to a combination of air and fire. It follows from what has
been said that no non-sanguineous animals have either lard or suet; for they have no blood. Among
sanguineous animals those whose blood is dense have suet rather than lard. For suet is of an earthy nature,
that is to say, it contains but a small proportion of water and is chiefly composed of earth; and this it is that
makes it coagulate, just as the fibrous matter of blood coagulates, or broths which contain such fibrous
matter. Thus it is that in those horned animals that have no front teeth in the upper jaw the fat consists of suet.
For the very fact that they have horns and huckle-bones shows that their composition is rich in this earthy
element; for all such appurtenances are solid and earthy in character. On the other hand in those hornless
animals that have front teeth in both jaws, and whose feet are divided into toes, there is no suet, but in its
place lard; and this, not being of an earthy character, neither coagulates nor dries up into a friable mass.

Both lard and suet when present in moderate amount are beneficial; for they contribute to health and strength,
while they are no hindrance to sensation. But when they are present in great excess, they are injurious and
destructive. For were the whole body formed of them it would perish. For an animal is an animal in virtue of
its sensory part, that is in virtue of its flesh, or of the substance analogous to flesh. But the blood, as before
stated, is not sensitive; as therefore is neither lard nor suet, seeing that they are nothing but concocted blood.
Were then the whole body composed of these substances, it would be utterly without sensation. Such
animals, again, as are excessively fat age rapidly. For so much of their blood is used in forming fat, that they
have but little left; and when there is but little blood the way is already open for decay. For decay may be said
to be deficiency of blood, the scantiness of which renders it liable, like all bodies of small bulk, to be
injuriously affected by any chance excess of heat or cold. For the same reason fat animals are less prolific
than others. For that part of the blood which should go to form semen and seed is used up in the production of
lard and suet, which are nothing but concocted blood; so that in these animals there is either no reproductive
excretion at all, or only a scanty amount.

So much then of blood and serum, and of lard and suet. Each of these has been described, and the purposes
told for which they severally exist. The marrow also is of the nature of blood, and not, as some think, the
germinal force of the semen. That this is the case is quite evident in very young animals. For in the embryo
the marrow of the bones has a blood-like appearance, which is but natural, seeing that the parts are all
constructed out of blood, and that it is on blood that the embryo is nourished. But, as the young animal grows
up and ripens into maturity, the marrow changes its colour, just as do the external parts and the viscera. For
the viscera also in animals, so long as they are young, have each and all a blood-like look, owing to the large
amount of this fluid which they contain.

The consistency of the marrow agrees with that of the fat. For when the fat consists of lard, then the marrow
also is unctuous and lard-like; but when the blood is converted by concoction into suet, and does not assume

5 18

ON THE PARTS OF ANIMALS

the form of lard, then the marrow also has a suety character. In those animals, therefore, that have horns and
are without upper front teeth, the marrow has the character of suet; while it takes the form of lard in those that
have front teeth in both jaws, and that also have the foot divided into toes. What has ben said hardly applies
to the spinal marrow. For it is necessary that this shall be continuous and extend without break through the
whole backbone, inasmuch as this bone consists of separate vertebrae. But were the spinal marrow either of
unctuous fat or of suet, it could not hold together in such a continuous mass as it does, but would either be too
fluid or too frangible.

There are some animals that can hardly be said to have any marrow. These are those whose bones are strong
and solid, as is the case with the lion. For in this animal the marrow is so utterly insignificant that the bones
look as though they had none at all. However, as it is necessary that animals shall have bones or something
analogous to them, such as the fish-spines of water-animals, it is also a matter of necessity that some of
these bones shall contain marrow; for the substance contained within the bones is the nutriment out of which
these are formed. Now the universal nutriment, as already stated, is blood; and the blood within the bone,
owing to the heat which is developed in it from its being thus surrounded, undergoes concoction, and
self-concocted blood is suet or lard; so that it is perfectly intelligible how the marrow within the bone comes
to have the character of these substances. So also it is easy to understand why, in those animals that have
strong and compact bones, some of these should be entirely void of marrow, while the rest contain but little
of it; for here the nutriment is spent in forming the bones.

Those animals that have fish-spines in place of bones have no other marrow than that of the chine. For in the
first place they have naturally but a small amount of blood; and secondly the only hollow fish-spine is that of
the chine. In this then marrow is formed; this being the only spine in which there is space for it, and,
moreover, being the only one which owing to its division into parts requires a connecting bond. This too is
the reason why the marrow of the chine, as already mentioned, is somewhat different from that of other
bones. For, having to act the part of a clasp, it must be of glutinous character, and at the same time sinewy so
as to admit of stretching.

Such then are the reasons for the existence of marrow, in those animals that have any, and such its nature. It
is evidently the surplus of the sanguineous nutriment apportioned to the bones and fish-spines, which has
undergone concoction owing to its being enclosed within them.

From the marrow we pass on in natural sequence to the brain. For there are many who think that the brain
itself consists of marrow, and that it forms the commencement of that substance, because they see that the
spinal marrow is continuous with it. In reality the two may be said to be utterly opposite to each other in
character. For of all the parts of the body there is none so cold as the brain; whereas the marrow is of a hot
nature, as is plainly shown by its fat and unctuous character. Indeed this is the very reason why the brain and
spinal marrow are continuous with each other. For, wherever the action of any part is in excess, nature so
contrives as to set by it another part with an excess of contrary action, so that the excesses of the two may
counterbalance each other. Now that the marrow is hot is clearly shown by many indications. The coldness of
the brain is also manifest enough. For in the first place it is cold even to the touch; and, secondly, of all the
fluid parts of the body it is the driest and the one that has the least blood; for in fact it has no blood at all in its
proper substance. This brain is not residual matter, nor yet is it one of the parts which are anatomically
continuous with each other; but it has a character peculiar to itself, as might indeed be expected. That it has
no continuity with the organs of sense is plain from simple inspection, and is still more clearly shown by the
fact, that, when it is touched, no sensation is produced; in which respect it resembles the blood of animals and
their excrement. The purpose of its presence in animals is no less than the preservation of the whole body.
For some writers assert that the soul is fire or some such force. This, however, is but a rough and inaccurate

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ON THE PARTS OF ANIMALS

assertion; and it would perhaps be better to say that the soul is incorporate in some substance of a fiery
character. The reason for this being so is that of all substances there is none so suitable for ministering to the
operations of the soul as that which is possessed of heat. For nutrition and the imparting of motion are offices
of the soul, and it is by heat that these are most readily effected. To say then that the soul is fire is much the
same thing as to confound the auger or the saw with the carpenter or his craft, simply because the work is
wrought by the two in conjunction. So far then this much is plain, that all animals must necessarily have a
certain amount of heat. But as all influences require to be counterbalanced, so that they may be reduced to
moderation and brought to the mean (for in the mean, and not in either extreme, lies the true and rational
position), nature has contrived the brain as a counterpoise to the region of the heart with its contained heat,
and has given it to animals to moderate the latter, combining in it the properties of earth and water. For this
reason it is, that every sanguineous animal has a brain; whereas no bloodless creature has such an organ,
unless indeed it be, as the Poulp, by analogy. For where there is no blood, there in consequence there is but
little heat. The brain, then, tempers the heat and seething of the heart. In order, however, that it may not itself
be absolutely without heat, but may have a moderate amount, branches run from both blood-vessels, that is
to say from the great vessel and from what is called the aorta, and end in the membrane which surrounds the
brain; while at the same time, in order to prevent any injury from the heat, these encompassing vessels,
instead of being few and large, are numerous and small, and their blood scanty and clear, instead of being
abundant and thick. We can now understand why defluxions have their origin in the head, and occur
whenever the parts about the brain have more than a due proportion of coldness. For when the nutriment
steams upwards through the blood-vessels, its refuse portion is chilled by the influence of this region, and
forms defluxions of phlegm and serum. We must suppose, to compare small things with great, that the like
happens here as occurs in the production of showers. For when vapour steams up from the earth and is carried
by the heat into the upper regions, so soon as it reaches the cold air that is above the earth, it condenses again
into water owing to the refrigeration, and falls back to the earth as rain. These, however, are matters which
may be suitably considered in the Principles of Diseases, so far as natural philosophy has anything to say to
them.

It is the brain again-or, in animals that have no brain, the part analogous to it-which is the cause of sleep. For
either by chilling the blood that streams upwards after food, or by some other similar influences, it produces
heaviness in the region in which it lies (which is the reason why drowsy persons hang the head), and causes
the heat to escape downwards in company with the blood. It is the accumulation of this in excess in the lower
region that produces complete sleep, taking away the power of standing upright from those animals to whom
that posture is natural, and from the rest the power of holding up the head. These, however, are matters which
have been separately considered in the treatises on Sensation and on Sleep.

That the brain is a compound of earth and water is shown by what occurs when it is boiled. For, when so
treated, it turns hard and solid, inasmuch as the water is evaporated by the heat, and leaves the earthy part
behind. Just the same occurs when pulse and other fruits are boiled. For these also are hardened by the
process, because the water which enters into their composition is driven off and leaves the earth, which is
their main constituent, behind.

Of all animals, man has the largest brain in proportion to his size; and it is larger in men than in women. This
is because the region of the heart and of the lung is hotter and richer in blood in man than in any other animal;
and in men than in women. This again explains why man, alone of animals, stands erect. For the heat,
overcoming any opposite inclination, makes growth take its own line of direction, which is from the centre of
the body upwards. It is then as a counterpoise to his excessive heat that in man's brain there is this
superabundant fluidity and coldness; and it is again owing to this superabundance that the cranial bone, which
some call the Bregma, is the last to become solidified; so long does evaporation continue to occur through it
under the influence of heat. Man is the only sanguineous animal in which this takes place. Man, again, has
more sutures in his skull than any other animal, and the male more than the female. The explanation is again
to be found in the greater size of the brain, which demands free ventilation, proportionate to its bulk. For if

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ON THE PARTS OF ANIMALS

the brain be either too fluid or too solid, it will not perform its office, but in the one case will freeze the
blood, and in the other will not cool it at all; and thus will cause disease, madness, and death. For the cardiac
heat and the centre of life is most delicate in its sympathies, and is immediately sensitive to the slightest
change or affection of the blood on the outer surface of the brain.

The fluids which are present in the animal body at the time of birth have now nearly all been considered.
Amongst those that appear only at a later period are the residua of the food, which include the deposits of the
belly and also those of the bladder. Besides these there is the semen and the milk, one or the other of which
makes its appearance in appropriate animals. Of these fluids the excremental residua of the food may be
suitably discussed by themselves, when we come to examine and consider the subject of nutrition. Then will
be the time to explain in what animals they are found, and what are the reasons for their presence. Similarly
all questions concerning the semen and the milk may be dealt with in the treatise on Generation, for the
former of these fluids is the very starting-point of the generative process, and the latter has no other ground
of existence than generative purposes.

We have now to consider the remaining homogeneous parts, and will begin with flesh, and with the substance
that, in animals that have no flesh, takes its place. The reason for so beginning is that flesh forms the very
basis of animals, and is the essential constituent of their body. Its right to this precedence can also be
demonstrated logically. For an animal is by our definition something that has sensibility and chief of all the
primary sensibility, which is that of Touch; and it is the flesh, or analogous substance, which is the organ of
this sense. And it is the organ, either in the same way as the pupil is the organ of sight, that is it constitutes
the primary organ of the sense; or it is the organ and the medium through which the object acts combined,
that is it answers to the pupil with the whole transparent medium attached to it. Now in the case of the other
senses it was impossible for nature to unite the medium with the sense-organ, nor would such a junction have
served any purpose; but in the case of touch she was compelled by necessity to do so. For of all the
sense-organs that of touch is the only one that has corporeal substance, or at any rate it is more corporeal
than any other, and its medium must be corporeal like itself.

It is obvious also to sense that it is for the sake of the flesh that all the other parts exist. By the other parts I
mean the bones, the skin, the sinews, and the blood-vessels, and, again, the hair and the various kinds of
nails, and anything else there may be of a like character. Thus the bones are a contrivance to give security to
the soft parts, to which purpose they are adapted by their hardness; and in animals that have no bones the
same office is fulfilled by some analogous substance, as by fishspine in some fishes, and by cartilage in
others.

Now in some animals this supporting substance is situated within the body, while in some of the bloodless
species it is placed on the outside. The latter is the case in all the Crustacea, as the Carcini (Crabs) and the
Carabi (Prickly Lobsters); it is the case also in the Testacea, as for instance in the several species known by
the general name of oysters. For in all these animals the fleshy substance is within, and the earthy matter,
which holds the soft parts together and keeps them from injury, is on the outside. For the shell not only
enables the soft parts to hold together, but also, as the animal is bloodless and so has but little natural warmth,
surrounds it, as a chaufferette does the embers, and keeps in the smouldering heat. Similar to this seems to be
the arrangement in another and distinct tribe of animals, namely the Tortoises, including the Chelone and the
several kinds of Emys. But in Insects and in Cephalopods the plan is entirely different, there being moreover
a contrast between these two themselves. For in neither of these does there appear to be any bony or earthy
part, worthy of notice, distinctly separated from the rest of the body. Thus in the Cephalopods the main bulk
of the body consists of a soft flesh-like substance, or rather of a substance which is intermediate to flesh and
sinew, so as not to be so readily destructible as actual flesh. I call this substance intermediate to flesh and

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ON THE PARTS OF ANIMALS

sinew, because it is soft like the former, while it admits of stretching like the latter. Its cleavage, however, is
such that it splits not longitudinally, like sinew, but into circular segments, this being the most advantageous
condition, so far as strength is concerned. These animals have also a part inside them corresponding to the
spinous bones of fishes. For instance, in the Cuttle-fishes there is what is known as the os sepiae, and in the
Calamaries there is the so-called gladius. In the Poulps, on the other hand, there is no such internal part,
because the body, or, as it is termed in them, the head, forms but a short sac, whereas it is of considerable
length in the other two; and it was this length which led nature to assign to them their hard support, so as to
ensure their straightness and inflexibility; just as she has assigned to sanguineous animals their bones or their
fish-spines, as the case may be. To come now to Insects. In these the arrangement is quite different from that
of the Cephalopods; quite different also from that which obtains in sanguineous animals, as indeed has been
already stated. For in an insect there is no distinction into soft and hard parts, but the whole body is hard, the
hardness, however, being of such a character as to be more flesh-like than bone, and more earthy and
bone-like than flesh. The purpose of this is to make the body of the insect less liable to get broken into
pieces.

There is a resemblance between the osseous and the vascular systems; for each has a central part in which it
begins, and each forms a continuous whole. For no bone in the body exists as a separate thing in itself, but
each is either a portion of what may be considered a continuous whole, or at any rate is linked with the rest by
contact and by attachments; so that nature may use adjoining bones either as though they were actually
continuous and formed a single bone, or, for purposes of flexure, as though they were two and distinct. And
similarly no blood-vessel has in itself a separate individuality; but they all form parts of one whole. For an
isolated bone, if such there were, would in the first place be unable to perform the office for the sake of which
bones exist; for, were it discontinuous and separated from the rest by a gap, it would be perfectly unable to
produce either flexure or extension; nor only so, but it would actually be injurious, acting like a thorn or an
arrow lodged in the flesh. Similarly if a vessel were isolated, and not continuous with the vascular centre, it
would be unable to retain the blood within it in a proper state. For it is the warmth derived from this centre
that hinders the blood from coagulating; indeed the blood, when withdrawn from its influence, becomes
manifestly putrid. Now the centre or origin of the blood-vessels is the heart, and the centre or origin of the
bones, in all animals that have bones, is what is called the chine. With this all the other bones of the body are
in continuity; for it is the chine that holds together the whole length of an animal and preserves its
straightness. But since it is necessary that the body of an animal shall bend during locomotion, this chine,
while it is one in virtue of the continuity of its parts, yet its division into vertebrae is made to consist of many
segments. It is from this chine that the bones of the limbs, in such animals as have these parts, proceed, and
with it they are continuous, being fastened together by the sinews where the limbs admit of flexure, and
having their extremities adapted to each other, either by the one being hollowed and the other rounded, or by
both being hollowed and including between them a hucklebone, as a connecting bolt, so as to allow of flexure
and extension. For without some such arrangement these movements would be utterly impossible, or at any
rate would be performed with great difficulty. There are some joints, again, in which the lower end of the one
bone and the upper end of the other are alike in shape. In these cases the bones are bound together by sinews,
and cartilaginous pieces are interposed in the joint, to serve as a kind of padding, and prevent the two
extremities from grating against each other.

Round about the bones, and attached to them by thin fibrous bands, grow the fleshy parts, for the sake of
which the bones themselves exist. For just as an artist, when he is moulding an animal out of clay or other
soft substance, takes first some solid body as a basis, and round this moulds the clay, so also has nature acted
in fashioning the animal body out of flesh. Thus we find all the fleshy parts, with one exception, supported by
bones, which serve, when the parts are organs of motion, to facilitate flexure, and, when the parts are
motionless, act as a protection. The ribs, for example, which enclose the chest are intended to ensure the

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ON THE PARTS OF ANIMALS

safety of the heart and neighbouring viscera. The exception of which mention was made is the belly. The
walls of this are in all animals devoid of bones; in order that there may be no hindrance to the expansion
which necessarily occurs in this part after a meal, nor, in females, any interference with the growth of the
foetus, which is lodged here.

Now the bones of viviparous animals, of such, that is, as are not merely externally but also internally
viviparous, vary but very little from each other in point of strength, which in all of them is considerable. For
the Vivipara in their bodily proportions are far above other animals, and many of them occasionally grow to
an enormous size, as is the case in Libya and in hot and dry countries generally. But the greater the bulk of an
animal, the stronger, the bigger, and the harder, are the supports which it requires; and comparing the big
animals with each other, this requirement will be most marked in those that live a life of rapine. Thus it is that
the bones of males are harder than those of females; and the bones of flesh-eaters, that get their food by
fighting, are harder than those of Herbivora. Of this the Lion is an example; for so hard are its bones, that,
when struck, they give off sparks, as though they were stones. It may be mentioned also that the Dolphin, in
as much as it is viviparous, is provided with bones and not with fish-spines.

In those sanguineous animals, on the other hand, that are oviparous, the bones present successive slight
variations of character. Thus in Birds there are bones, but these are not so strong as the bones of the Vivipara.
Then come the Oviparous fishes, where there is no bone, but merely fish-spine. In the Serpents too the bones
have the character of fish-spine, excepting in the very large species, where the solid foundation of the body
requires to be stronger, in order that the animal itself may be strong, the same reason prevailing as in the case
of the Vivipara. Lastly, in the Selachia, as they are called, the fish-spines are replaced by cartilage. For it is
necessary that the movements of these animals shall be of an undulating character; and this again requires the
framework that supports the body to be made of a pliable and not of a brittle substance. Moreover, in these
Selachia nature has used all the earthy matter on the skin; and she is unable to allot to many different parts
one and the same superfluity of material. Even in viviparous animals many of the bones are cartilaginous.
This happens in those parts where it is to the advantage of the surrounding flesh that its solid base shall be
soft and mucilaginous. Such, for instance, is the case with the ears and nostrils; for in projecting parts, such as
these, brittle substances would soon get broken. Cartilage and bone are indeed fundamentally the same thing,
the differences between them being merely matters of degree. Thus neither cartilage nor bone, when once cut
off, grows again. Now the cartilages of these land animals are without marrow, that is without any distinctly
separate marrow. For the marrow, which in bones is distinctly separate, is here mixed up with the whole
mass, and gives a soft and mucilaginous consistence to the cartilage. But in the Selachia the chine, though it
is cartilaginous, yet contains marrow; for here it stands in the stead of a bone.

Very nearly resembling the bones to the touch are such parts as nails, hoofs, whether solid or cloven, horns,
and the beaks of birds, all of which are intended to serve as means of defence. For the organs which are made
out of these substances, and which are called by the same names as the substances themselves, the organ
hoof, for instance, and the organ horn, are contrivances to ensure the preservation of the animals to which
they severally belong. In this class too must be reckoned the teeth, which in some animals have but a single
function, namely the mastication of the food, while in others they have an additional office, namely to serve
as weapons; as is the case with all animals that have sharp interfitting teeth or that have tusks. All these parts
are necessarily of solid and earthy character; for the value of a weapon depends on such properties. Their
earthy character explains how it is that all such parts are more developed in four-footed vivipara than in man.
For there is always more earth in the composition of these animals than in that of the human body. However,
not only all these parts but such others as are nearly connected with them, skin for instance, bladder,
membrane, hairs, feathers, and their analogues, and any other similar parts that there may be, will be
considered farther on with the heterogeneous parts. There we shall inquire into the causes which produce
them, and into the objects of their presence severally in the bodies of animals. For, as with the heterogeneous
parts, so with these, it is from a consideration of their functions that alone we can derive any knowledge of
them. The reason for dealing with them at all in this part of the treatise, and classifying them with the

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ON THE PARTS OF ANIMALS

homogeneous parts, is that under one and the same name are confounded the entire organs and the substances
of which they are composed. But of all these substances flesh and bone form the basis. Semen and milk were
also passed over when we were considering the homogeneous fluids. For the treatise on Generation will
afford a more suitable place for their examination, seeing that the former of the two is the very foundation of
the thing generated, while the latter is its nourishment.

Let us now make, as it were, a fresh beginning, and consider the heterogeneous parts, taking those first which
are the first in importance. For in all animals, at least in all the perfect kinds, there are two parts more
essential than the rest, namely the part which serves for the ingestion of food, and the part which serves for
the discharge of its residue. For without food growth and even existence is impossible. Intervening again
between these two parts there is invariably a third, in which is lodged the vital principle. As for plants, though
they also are included by us among things that have life, yet are they without any part for the discharge of
waste residue. For the food which they absorb from the ground is already concocted, and they give off as its
equivalent their seeds and fruits. Plants, again, inasmuch as they are without locomotion, present no great
variety in their heterogeneous parts. For, where the functions are but few, few also are the organs required to
effect them. The configuration of plants is a matter then for separate consideration. Animals, however, that
not only live but feel, present a greater multiformity of parts, and this diversity is greater in some animals
than in others, being most varied in those to whose share has fallen not mere life but life of high degree. Now
such an animal is man. For of all living beings with which we are acquainted man alone partakes of the
divine, or at any rate partakes of it in a fuller measure than the rest. For this reason, then, and also because his
external parts and their forms are more familiar to us than those of other animals, we must speak of man first;
and this the more fitly, because in him alone do the natural parts hold the natural position; his upper part
being turned towards that which is upper in the universe. For, of all animals, man alone stands erect.

In man, then, the head is destitute of flesh; this being the necessary consequence of what has already been
stated concerning the brain. There are, indeed, some who hold that the life of man-would be longer than it is,
were his head more abundantly furnished with flesh; and they account for the absence of this substance by
saying that it is intended to add to the perfection of sensation. For the brain they assert to be the organ of
sensation; and sensation, they say, cannot penetrate to parts that are too thickly covered with flesh. But
neither part of this statement is true. On the contrary, were the region of the brain thickly covered with flesh,
the very purpose for which animals are provided with a brain would be directly contravened. For the brain
would itself be heated to excess and so unable to cool any other part; and, as to the other half of their
statement, the brain cannot be the cause of any of the sensations, seeing that it is itself as utterly without
feeling as any one of the excretions. These writers see that certain of the senses are located in the head, and
are unable to discern the reason for this; they see also that the brain is the most peculiar of all the animal
organs; and out of these facts they form an argument, by which they link sensation and brain together. It has,
however, already been clearly set forth in the treatise on Sensation, that it is the region of the heart that
constitutes the sensory centre. There also it was stated that two of the senses, namely touch and taste, are
manifestly in immediate connexion with the heart; and that as regards the other three, namely hearing, sight,
and the centrally placed sense of smell, it is the character of their sense-organs which causes them to be
lodged as a rule in the head. Vision is so placed in all animals. But such is not invariably the case with
hearing or with smell. For fishes and the like hear and smell, and yet have no visible organs for these senses
in the head; a fact which demonstrates the accuracy of the opinion here maintained. Now that vision,
whenever it exists, should be in the neighbourhood of the brain is but what one would rationally expect. For
the brain is fluid and cold, and vision is of the nature of water, water being of all transparent substances the
one most easily confined. Moreover it cannot but necessarily be that the more precise senses will have their
precision rendered still greater if ministered to by parts that have the purest blood. For the motion of the heat
of blood destroys sensory activity. For these reasons the organs of the precise senses are lodged in the head.

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ON THE PARTS OF ANIMALS

It is not only the fore part of the head that is destitute of flesh, but the hind part also. For, in all animals that
have a head, it is this head which more than any other part requires to be held up. But, were the head heavily
laden with flesh, this would be impossible; for nothing so burdened can be held upright. This is an additional
proof that the absence of flesh from the head has no reference to brain sensation. For there is no brain in the
hinder part of the head, and yet this is as much without flesh as is the front.

In some animals hearing as well as vision is lodged in the region of the head. Nor is this without a rational
explanation. For what is called the empty space is full of air, and the organ of hearing is, as we say, of the
nature of air. Now there are channels which lead from the eyes to the blood-vessels that surround the brain;
and similarly there is a channel which leads back again from each ear and connects it with the hinder part of
the head. But no part that is without blood is endowed with sensation, as neither is the blood itself, but only
some one of the parts that are formed of blood.

The brain in all animals that have one is placed in the front part of the head; because the direction in which
sensation acts is in front; and because the heart, from which sensation proceeds, is in the front part of the
body; and lastly because the instruments of sensation are the blood-containing parts, and the cavity in the
posterior part of the skull is destitute of blood-vessels.

As to the position of the sense-organs, they have been arranged by nature in the following well-ordered
manner. The organs of hearing are so placed as to divide the circumference of the head into two equal halves;
for they have to hear not only sounds which are directly in line with themselves, but sounds from all quarters.
The organs of vision are placed in front, because sight is exercised only in a straight line, and moving as we
do in a forward direction it is necessary that we should see before us, in the direction of our motion. Lastly,
the organs of smell are placed with good reason between the eyes. For as the body consists of two parts, a
right half and a left, so also each organ of sense is double. In the case of touch this is not apparent, the reason
being that the primary organ of this sense is not the flesh or analogous part, but lies internally. In the case of
taste, which is merely a modification of touch and which is placed in the tongue, the fact is more apparent
than in the case of touch, but still not so manifest as in the case of the other senses. However, even in taste it
is evident enough; for in some animals the tongue is plainly forked. The double character of the sensations is,
however, more conspicuous in the other organs of sense. For there are two ears and two eyes, and the nostrils,
though joined together, are also two. Were these latter otherwise disposed, and separated from each other as
are the ears, neither they nor the nose in which they are placed would be able to perform their office. For in
such animals as have nostrils olfaction is effected by means of inspiration, and the organ of inspiration is
placed in front and in the middle line. This is the reason why nature has brought the two nostrils together and
placed them as the central of the three sense-organs, setting them side by side on a level with each other, to
avail themselves of the inspiratory motion. In other animals than man the arrangement of these sense-organs
is also such as is adapted in each case to the special requirements.

For instance, in quadrupeds the ears stand out freely from the head and are set to all appearance above the
eyes. Not that they are in reality above the eyes; but they seem to be so, because the animal does not stand
erect, but has its head hung downwards. This being the usual attitude of the animal when in motion, it is of
advantage that its ears shall be high up and movable; for by turning themselves about they can the better take
in sounds from every quarter.

In birds, on the other hand, there are no ears, but only the auditory passages. This is because their skin is hard
and because they have feathers instead of hairs, so that they have not got the proper material for the formation

11 25

ON THE PARTS OF ANIMALS

of ears. Exactly the same is the case with such oviparous quadrupeds as are clad with scaly plates, and the
same explanation applies to them. There is also one of the viviparous quadrupeds, namely the seal, that has
no ears but only the auditory passages. The explanation of this is that the seal, though a quadruped, is a
quadruped of stunted formation.

Men, and Birds, and Quadrupeds, viviparous and oviparous alike, have their eyes protected by lids. In the
Vivipara there are two of these; and both are used by these animals not only in closing the eyes, but also in
the act of blinking; whereas the oviparous quadrupeds, and the heavy-bodied birds as well as some others,
use only the lower lid to close the eye; while birds blink by means of a membrane that issues from the
canthus. The reason for the eyes being thus protected is that nature has made them of fluid consistency, in
order to ensure keenness of vision. For had they been covered with hard skin, they would, it is true, have been
less liable to get injured by anything falling into them from without, but they would not have been
sharp-sighted. It is then to ensure keenness of vision that the skin over the pupil is fine and delicate; while
the lids are superadded as a protection from injury. It is as a still further safeguard that all these animals blink,
and man most of all; this action (which is not performed from deliberate intention but from a natural instinct)
serving to keep objects from falling into the eyes; and being more frequent in man than in the rest of these
animals, because of the greater delicacy of his skin. These lids are made of a roll of skin; and it is because
they are made of skin and contain no flesh that neither they, nor the similarly constructed prepuce, unite again
when once cut.

As to the oviparous quadrupeds, and such birds as resemble them in closing the eye with the lower lid, it is
the hardness of the skin of their heads which makes them do so. For such birds as have heavy bodies are not
made for flight; and so the materials which would otherwise have gone to increase the growth of the feathers
are diverted thence, and used to augment the thickness of the skin. Birds therefore of this kind close the eye
with the lower lid; whereas pigeons and the like use both upper and lower lids for the purpose. As birds are
covered with feathers, so oviparous quadrupeds are covered with scaly plates; and these in all their forms are
harder than hairs, so that the skin also to which they belong is harder than the skin of hairy animals. In these
animals, then, the skin on the head is hard, and so does not allow of the formation of an upper eyelid, whereas
lower down the integument is of a flesh-like character, so that the lower lid can be thin and extensible.

The act of blinking is performed by the heavy-bodied birds by means of the membrane already mentioned,
and not by this lower lid. For in blinking rapid motion is required, and such is the motion of this membrane,
whereas that of the lower lid is slow. It is from the canthus that is nearest to the nostrils that the membrane
comes. For it is better to have one starting-point for nictitation than two; and in these birds this starting-point
is the junction of eye and nostrils, an anterior starting-point being preferable to a lateral one. Oviparous
quadrupeds do not blink in like manner as the birds; for, living as they do on the ground, they are free from
the necessity of having eyes of fluid consistency and of keen sight, whereas these are essential requisites for
birds, inasmuch as they have to use their eyes at long distances. This too explains why birds with talons, that
have to search for prey by eye from aloft, and therefore soar to greater heights than other birds, are
sharpsighted; while common fowls and the like, that live on the ground and are not made for flight, have no
such keenness of vision. For there is nothing in their mode of life which imperatively requires it.

Fishes and Insects and the hard-skinned Crustacea present certain differences in their eyes, but so far
resemble each other as that none of them have eyelids. As for the hard-skinned Crustacea it is utterly out of
the question that they should have any; for an eyelid, to be of use, requires the action of the skin to be rapid.
These animals then have no eyelids and, in default of this protection, their eyes are hard, just as though the lid
were attached to the surface of the eye, and the animal saw through it. Inasmuch, however, as such hardness
must necessarily blunt the sharpness of vision, nature has endowed the eyes of Insects, and still more those of

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ON THE PARTS OF ANIMALS

Crustacea, with mobility (just as she has given some quadrupeds movable ears), in order that they may be
able to turn to the light and catch its rays, and so see more plainly. Fishes, however, have eyes of a fluid
consistency. For animals that move much about have to use their vision at considerable distances. If now they
live on land, the air in which they move is transparent enough. But the water in which fishes live is a
hindrance to sharp sight, though it has this advantage over the air, that it does not contain so many objects to
knock against the eyes. The risk of collision being thus small, nature, who makes nothing in vain, has given
no eyelids to fishes, while to counterbalance the opacity of the water she has made their eyes of fluid
consistency.

All animals that have hairs on the body have lashes on the eyelids; but birds and animals with scale-like
plates, being hairless, have none. The Libyan ostrich, indeed, forms an exception; for, though a bird, it is
furnished with eyelashes. This exception, however, will be explained hereafter. Of hairy animals, man alone
has lashes on both lids. For in quadrupeds there is a greater abundance of hair on the back than on the under
side of the body; whereas in man the contrary is the case, and the hair is more abundant on the front surface
than on the back. The reason for this is that hair is intended to serve as a protection to its possessor. Now, in
quadrupeds, owing to their inclined attitude, the under or anterior surface does not require so much protection
as the back, and is therefore left comparatively bald, in spite of its being the nobler of the two sides. But in
man, owing to his upright attitude, the anterior and posterior surfaces of the body are on an equality as
regards need of protection. Nature therefore has assigned the protective covering to the nobler of the two
surfaces; for invariably she brings about the best arrangement of such as are possible. This then is the reason
that there is no lower eyelash in any quadruped; though in some a few scattered hairs sprout out under the
lower lid. This also is the reason that they never have hair in the axillae, nor on the pubes, as man has. Their
hair, then, instead of being collected in these parts, is either thickly set over the whole dorsal surface, as is the
case for instance in dogs, or, sometimes, forms a mane, as in horses and the like, or as in the male lion where
the mane is still more flowing and ample. So, again, whenever there is a tail of any length, nature decks it
with hair, with long hair if the stem of the tail be short, as in horses, with short hair if the stem be long, regard
also being had to the condition of the rest of the body. For nature invariably gives to one part what she
subtracts from another. Thus when she has covered the general surface of an animal's body with an excess of
hair, she leaves a deficiency in the region of the tail. This, for instance, in the case with bears.

No animal has so much hair on the head as man. This, in the first place, is the necessary result of the fluid
character of his brain, and of the presence of so many sutures in his skull. For wherever there is the most fluid
and the most heat, there also must necessarily occur the greatest outgrowth. But, secondly, the thickness of
the hair in this part has a final cause, being intended to protect the head, by preserving it from excess of either
heat or cold. And as the brain of man is larger and more fluid than that of any other animal, it requires a
proportionately greater amount of protection. For the more fluid a substance is, the more readily does it get
excessively heated or excessively chilled, while substances of an opposite character are less liable to such
injurious affections.

These, however, are matters which by their close connexion with eyelashes have led us to digress from our
real topic, namely the cause to which these lashes owe their existence. We must therefore defer any further
remarks we may have to make on these matters till the proper occasion arises and then return to their
consideration.

Both eyebrows and eyelashes exist for the protection of the eyes; the former that they may shelter them, like
the eaves of a house, from any fluids that trickle down from the head; the latter to act like the palisades which

14 27

ON THE PARTS OF ANIMALS

are sometimes placed in front of enclosures, and keep out any objects which might otherwise get in. The
brows are placed over the junction of two bones, which is the reason that in old age they often become so
bushy as to require cutting. The lashes are set at the terminations of small blood-vessels. For the vessels
come to an end where the skin itself terminates; and, in all places where these endings occur, the exudation of
moisture of a corporeal character necessitates the growth of hairs, unless there be some operation of nature
which interferes, by diverting the moisture to another purpose.

Viviparous quadrupeds, as a rule, present no great variety of form in the organ of smell. In those of them,
however, whose jaws project forwards and taper to a narrow end, so as to form what is called a snout, the
nostrils are placed in this projection, there being no other available plan; while, in the rest, there is a more
definite demarcation between nostrils and jaws. But in no animal is this part so peculiar as in the elephant,
where it attains an extraordinary and strength. For the elephant uses its nostril as a hand; this being the
instrument with which it conveys food, fluid and solid alike, to its mouth. With it, too, it tears up trees,
coiling it round their stems. In fact it applies it generally to the purposes of a hand. For the elephant has the
double character of a land animal, and of one that lives in swamps. Seeing then that it has to get its food from
the water, and yet must necessarily breathe, inasmuch as it is a land animal and has blood; seeing, also, that
its excessive weight prevents it from passing rapidly from water to land, as some other sanguineous vivipara
that breathe can do, it becomes necessary that it shall be suited alike for life in the water and for life on dry
land, just then as divers are sometimes provided with instruments for respiration, through which they can
draw air from above the water, and thus may remain for a long time under the sea, so also have elephants
been furnished by nature with their lengthened nostril; and, whenever they have to traverse the water, they lift
this up above the surface and breathe through it. For the elephant's proboscis, as already said, is a nostril.
Now it would have been impossible for this nostril to have the form of a proboscis, had it been hard and
incapable of bending. For its very length would then have prevented the animal from supplying itself with
food, being as great an impediment as the of certain oxen, that are said to be obliged to walk backwards while
they are grazing. It is therefore soft and flexible, and, being such, is made, in addition to its own proper
functions, to serve the office of the fore-feet; nature in this following her wonted plan of using one and the
same part for several purposes. For in polydactylous quadrupeds the fore-feet are intended not merely to
support the weight of the body, but to serve as hands. But in elephants, though they must be reckoned
polydactylous, as their foot has neither cloven nor solid hoof, the fore-feet, owing to the great size and
weight of the body, are reduced to the condition of mere supports; and indeed their slow motion and unfitness
for bending make them useless for any other purpose. A nostril, then, is given to the elephant for respiration,
as to every other animal that has a lung, and is lengthened out and endowed with its power of coiling because
the animal has to remain for considerable periods of time in the water, and is unable to pass thence to dry
ground with any rapidity. But as the feet are shorn of their full office, this same part is also, as already said,
made by nature to supply their place, and give such help as otherwise would be rendered by them.

As to other sanguineous animals, the Birds, the Serpents, and the Oviparous quadrupeds, in all of them there
are the nostril-holes, placed in front of the mouth; but in none are there any distinctly formed nostrils,
nothing in fact which can be called nostrils except from a functional point of view. A bird at any rate has
nothing which can properly be called a nose. For its so-called beak is a substitute for jaws. The reason for
this is to be found in the natural conformation of birds. For they are winged bipeds; and this makes it
necessary that their heads and neck shall be of light weight; just as it makes it necessary that their breast shall
be narrow. The beak therefore with which they are provided is formed of a bone-like substance, in order that
it may serve as a weapon as well as for nutritive purposes, but is made of narrow dimensions to suit the small
size of the head. In this beak are placed the olfactory passages. But there are no nostrils; for such could not
possibly be placed there.

16 28

ON THE PARTS OF ANIMALS

As for those animals that have no respiration, it has already been explained why it is that they are without
nostrils, and perceive odours either through gills, or through a blowhole, or, if they are insects, by the
hypozoma; and how the power of smelling depends, like their motion, upon the innate spirit of their bodies,
which in all of them is implanted by nature and not introduced from without.

Under the nostrils are the lips, in such sanguineous animals, that is, as have teeth. For in birds, as already has
been said, the purposes of nutrition and defence are fulfilled by a bonelike beak, which forms a compound
substitute for teeth and lips. For supposing that one were to cut off a man's lips, unite his upper teeth together,
and similarly his under ones, and then were to lengthen out the two separate pieces thus formed, narrowing
them on either side and making them project forwards, supposing, I say, this to be done, we should at once
have a bird-like beak.

The use of the lips in all animals except man is to preserve and guard the teeth; and thus it is that the
distinctness with which the lips are formed is in direct proportion to the degree of nicety and perfection with
which the teeth are fashioned. In man the lips are soft and flesh-like and capable of separating from each
other. Their purpose, as in other animals, is to guard the teeth, but they are more especially intended to serve
a higher office, contributing in common with other parts to man's faculty of speech. For just as nature has
made man's tongue unlike that of other animals, and, in accordance with what I have said is her not
uncommon practice, has used it for two distinct operations, namely for the perception of savours and for
speech, so also has she acted with regard to the lips, and made them serve both for speech and for the
protection of the teeth. For vocal speech consists of combinations of the letters, and most of these would be
impossible to pronounce, were the lips not moist, nor the tongue such as it is. For some letters are formed by
closures of the lips and others by applications of the tongue. But what are the differences presented by these
and what the nature and extent of such differences, are questions to which answers must be sought from those
who are versed in metrical science. It was necessary that the two parts which we are discussing should, in
conformity with the requirements, be severally adapted to fulfil the office mentioned above, and be of
appropriate character. Therefore are they made of flesh, and flesh is softer in man than in any other animal,
the reason for this being that of all animals man has the most delicate sense of touch.

The tongue is placed under the vaulted roof of the mouth. In land animals it presents but little diversity. But
in other animals it is variable, and this whethe+r we compare them as a class with such as live on land, or
compare their several species with each other. It is in man that the tongue attains its greatest degree of
freedom, of softness, and of breadth; the object of this being to render it suitable for its double function. For
its softness fits it for the perception of savours, a sense which is more delicate in man than in any other
animal, softness being most impressionable by touch, of which sense taste is but a variety. This same softness
again, together with its breadth, adapts it for the articulation of letters and for speech. For these qualities,
combined with its freedom from attachment, are those which suit it best for advancing and retiring in every
direction. That this is so is plain, if we consider the case of those who are tongue-tied in however slight a
degree. For their speech is indistinct and lisping; that is to say there are certain letters which they cannot
pronounce. In being broad is comprised the possibility of becoming narrow; for in the great the small is
included, but not the great in the small.

What has been said explains why, among birds, those that are most capable of pronouncing letters are such as
have the broadest tongues; and why the viviparous and sanguineous quadrupeds, where the tongue is hard and
thick and not free in its motions, have a very limited vocal articulation. Some birds have a considerable
variety of notes. These are the smaller kinds. But it is the birds with talons that have the broader tongues. All
birds use their tongues to communicate with each other. But some do this in a greater degree than the rest; so
that in some cases it even seems as though actual instruction were imparted from one to another by its

17 29

ON THE PARTS OF ANIMALS

agency. These, however, are matters which have already been discussed in the Researches concerning
Animals.

As to those oviparous and sanguineous animals that live not in the air but on the earth, their tongue in most
cases is tied down and hard, and is therefore useless for vocal purposes; in the serpents, however, and in the
lizards it is long and forked, so as to be suited for the perception of savours. So long indeed is this part in
serpents, that though small while in the mouth it can be protruded to a great distance. In these animals it is
forked and has a fine and hair-like extremity, because of their great liking for dainty food. For by this
arrangement they derive a twofold pleasure from savours, their gustatory sensation being as it were doubled.

Even some bloodless animals have an organ that serves for the perception of savours; and in sanguineous
animals such an organ is invariably variably For even in such of these as would seem to an ordinary observer
to have nothing of the kind, some of the fishes for example, there is a kind of shabby representative of a
tongue, much like what exists in river crocodiles. In most of these cases the apparent absence of the part can
be rationally explained on some ground or other. For in the first place the interior of the mouth in animals of
this character is invariably spinous. Secondly, in water animals there is but short space of time for the
perception of savours, and as the use of this sense is thus of short duration, shortened also is the separate part
which subserves it. The reason for their food being so rapidly transmitted to the stomach is that they cannot
possibly spend any time in sucking out the juices; for were they to attempt to do so, the water would make its
way in during the process. Unless therefore one pulls their mouth very widely open, the projection of this part
is quite invisible. The region exposed by thus opening the mouth is spinous; for it is formed by the close
apposition of the gills, which are of a spinous character.

In crocodiles the immobility of the lower jaw also contributes in some measure to stunt the development of
the tongue. For the crocodile's tongue is adherent to the lower jaw. For its upper and lower jaws are, as it
were, inverted, it being the upper jaw which in other animals is the immovable one. The tongue, however, on
this animal is not attached to the upper jaw, because that would interfere with the ingestion of food, but
adheres to the lower jaw, because this is, as it were, the upper one which has changed its place. Moreover, it
is the crocodile's lot, though a land animal, to live the life of a fish, and this again necessarily involves an
indistinct formation of the part in question.

The roof of the mouth resembles flesh, even in many of the fishes; and in some of the river species, as for
instance in the fishes known as Cyprini, is so very flesh-like and soft as to be taken by careless observers for
a tongue. The tongue of fishes, however, though it exists as a separate part, is never formed with such
distinctness as this, as has been already explained. Again, as the gustatory sensibility is intended to serve
animals in the selection of food, it is not diffused equally over the whole surface of the tongue-like organ,
but is placed chiefly in the tip; and for this reason it is the tip which is the only part of the tongue separated in
fishes from the rest of the mouth. As all animals are sensible to the pleasure derivable from food, they all feel
a desire for it. For the object of desire is the pleasant. The part, however, by which food produces the
sensation is not precisely alike in all of them, but while in some it is free from attachments, in others, where it
is not required for vocal pur, poses, it is adherent. In some again it is hard, in others soft or flesh-like. Thus
even the Crustacea, the Carabi for instance and the like, and the Cephalopods, such as the Sepias and the
Poulps, have some such part inside the mouth. As for the Insects, some of them have the part which serves as
tongue inside the mouth, as is the case with ants, and as is also the case with many Testacea, while in others it
is placed externally. In this latter case it resembles a sting, and is hollow and spongy, so as to serve at one and
the same time for the tasting and for the sucking up of nutriment. This is plainly to be seen in flies and bees
and all such animals, and likewise in some of the Testacea. In the Purpurae, for instance, so strong is this part
that it enables them to bore holes through the hard covering of shell-fish, of the spiral snails, for example,
that are used as bait to catch them. So also the gad-flies and cattle-flies can pierce through the skin of man,
and some of them even through the skins of other animals. Such, then, in these animals is the nature of the
tongue, which is thus as it were the counterpart of the elephant's nostril. For as in the elephant the nostril is

17 30

ON THE PARTS OF ANIMALS

used as a weapon, so in these animals the tongue serves as a sting.
In all other animals the tongue agrees with description already given.

Book III

WE have next to consider the teeth, and with these the mouth, that is the cavity which they enclose and form.
The teeth have one invariable office, namely the reduction of food; but besides this general function they
have other special ones, and these differ in different groups. Thus in some animals the teeth serve as
weapons; but this with a distinction. For there are offensive weapons and there are defensive weapons; and
while in some animals, as the wild Carnivora, the teeth answer both purposes, in many others, both wild and
domesticated, they serve only for defence. In man the teeth are admirably constructed for their general office,
the front ones being sharp, so as to cut the food into bits, and the hinder ones broad and flat, so as to grind it
to a pulp; while between these and separating them are the dog-teeth, which, in accordance with the rule that
the mean partakes of both extremes, share in the characters of those on either side, being broad in one part but
sharp in another. Similar distinctions of shape are presented by the teeth of other animals, with the exception
of those whose teeth are one and all of the sharp kind. In man, however, the number and the character even of
these sharp teeth have been mainly determined by the requirements of speech. For the front teeth of man
contribute in many ways to the formation of letter-sounds.

In some animals, however, the teeth, as already said, serve merely for the reduction of food. When, besides
this, they serve as offensive and defensive weapons, they may either be formed into tusks, as for instance is
the case in swine, or may be sharp-pointed and interlock with those of the opposite jaw, in which case the
animal is said to be saw-toothed. The explanation of this latter arrangement is as follows. The strength of
such an animal is in its teeth, and these depend for their efficiency on their sharpness. In order, then, to
prevent their getting blunted by mutual friction, such of them as serve for weapons fit into each other's
interspaces, and are so kept in proper condition. No animal that has sharp interfitting teeth is at the same time
furnished with tusks. For nature never makes anything superfluous or in vain. She gives, therefore, tusks to
such animals as strike in fighting, and serrated teeth to such as bite. Sows, for instance, have no tusks, and
accordingly sows bite instead of striking.

A general principle must here be noted, which will be found applicable not only in this instance but in many
others that will occur later on. Nature allots each weapon, offensive and defensive alike, to those animals
alone that can use it; or, if not to them alone, to them in a more marked degree; and she allots it in its most
perfect state to those that can use it best; and this whether it be a sting, or a spur, or horns, or tusks, or what it
may of a like kind.

Thus as males are stronger and more choleric than females, it is in males that such parts as those just
mentioned are found, either exclusively, as in some species, or more fully developed, as in others. For though
females are of course provided with such parts as are no less necessary to them than to males, the parts, for
instance, which subserve nutrition, they have even these in an inferior degree, and the parts which answer no
such necessary purpose they do not possess at all. This explains why stags have horns, while does have none;
why the horns of cows are different from those of bulls, and, similarly, the horns of ewes from those of rams.
It explains also why the females are often without spurs in species where the males are provided with them,
and accounts for similar facts relating to all other such parts.

All fishes have teeth of the serrated form, with the single exception of the fish known as the Scarus. In many
of them there are teeth even on the tongue and on the roof of the mouth. The reason for this is that, living as

Book III 31

ON THE PARTS OF ANIMALS

they do in the water, they cannot but allow this fluid to pass into the mouth with the food. The fluid thus
admitted they must necessarily discharge again without delay. For were they not to do so, but to retain it for a
time while triturating the food, the water would run into their digestive cavities. Their teeth therefore are all
sharp, being adapted only for cutting, and are numerous and set in many parts, that their abundance may serve
in lieu of any grinding faculty, to mince the food into small bits. They are also curved, because these are
almost the only weapons which fishes possess.

In all these offices of the teeth the mouth also takes its part; but besides these functions it is subservient to
respiration, in all such animals as breathe and are cooled by external agency. For nature, as already said, uses
the parts which are common to all animals for many special purposes, and this of her own accord. Thus the
mouth has one universal function in all animals alike, namely its alimentary office; but in some, besides this,
the special duty of serving as a weapon is attached to it; in others that of ministering to speech; and again in
many, though not in all, the office of respiration. All these functions are thrown by nature upon one single
organ, the construction of which she varies so as to suit the variations of office. Therefore it is that in some
animals the mouth is contracted, while in others it is of wide dimensions. The contracted form belongs to
such animals as use the mouth merely for nutritive, respiratory, and vocal purposes; whereas in such as use it
as a means of defence it has a wide gape. This is its invariable form in such animals as are saw-toothed. For
seeing that their mode of warfare consists in biting, it is advantageous to them that their mouth shall have a
wide opening; for the wider it opens, the greater will be the extent of the bite, and the more numerous will be
the teeth called into play.

What has just been said applies to fishes as well as to other animals; and thus in such of them as are
carnivorous, and made for biting, the mouth has a wide gape; whereas in the rest it is small, being placed at
the extremity of a tapering snout. For this form is suited for their purposes, while the other would be useless.

In birds the mouth consists of what is called the beak, which in them is a substitute for lips and teeth. This
beak presents variations in harmony with the functions and protective purposes which it serves. Thus in those
birds that are called Crooked-clawed it is invariably hooked, inasmuch as these birds are carnivorous, and eat
no kind of vegetable food whatsoever. For this form renders it serviceable to them in obtaining the mastery
over their prey, and is better suited for deeds of violence than any other. Moreover, as their weapons of
offence consist of this beak and of their claws, these latter also are more crooked in them than in the
generality of birds. Similarly in each other kind of bird the beak is suited to the mode of life. Thus, in
woodpeckers it is hard and strong, as also in crows and birds of crowlike habit, while in the smaller birds it is
delicate, so as to be of use in collecting seeds and picking up minute animals. In such birds, again, as eat
herbage, and such as live about marshes-those, for example, that swim and have webbed feet-the bill is
broad, or adapted in some other way to the mode of life. For a broad bill enables a bird to dig into the ground
with ease, just as, among quadrupeds, does the broad snout of the pig, an animal which, like the birds in
question, lives on roots. Moreover, in these root-eating birds and in some others of like habits of life, the tips
of the bill end in hard points, which gives them additional facility in dealing with herbaceous food.

The several parts which are set on the head have now, pretty nearly all, been considered. In man, however,
the part which lies between the head and the neck is called the face, this name, (prosopon) being, it would
seem, derived from the function of the part. For as man is the only animal that stands erect, he is also the only
one that looks directly in front (proso) and the only one whose voice is emitted in that direction.

We have now to treat of horns; for these also, when present, are appendages of the head. They exist in none
but viviparous animals; though in some ovipara certain parts are metaphorically spoken of as horns, in virtue
of a certain resemblance. To none of such parts, however, does the proper office of a horn belong; for they

2 32

ON THE PARTS OF ANIMALS

are never used, as are the horns of vivipara, for purposes which require strength, whether it be in
self-protection or in offensive strife. So also no polydactylous animal is furnished with horns. For horns are
defensive weapons, and these polydactylous animals possess other means of security. For to some of them
nature has given claws, to others teeth suited for combat, and to the rest some other adequate defensive
appliance. There are horns, however, in most of the cloven-hoofed animals, and in some of those that have a
solid hoof, serving them as an offensive weapon, and in some cases also as a defensive one. There are horns
also in all animals that have not been provided by nature with some other means of security; such means, for
instance, as speed, which has been given to horses; or great size, as in camels; for excessive bulk, such as has
been given to these animals, and in a still greater measure to elephants, is sufficient in itself to protect an
animal from being destroyed by others. Other animals again are protected by the possession of tusks; and
among these are the swine, though they have a cloven hoof.

All animals again, whose horns are but useless appendages, have been provided by nature with some
additional means of security. Thus deer are endowed with speed; for the large size and great branching of
their horns makes these a source of detriment rather than of profit to their possessors. Similarly endowed are
the Bubalus and gazelle; for though these animals will stand up against some enemies and defend themselves
with their horns, yet they run away from such as are fierce and pugnacious. The Bonasus again, whoe horns
curve inwards towards each other, is provided with a means of protection in the discharge of its excrement;
and of this it avails itself when frightened. There are some other animals besides the Bonasus that have a
similar mode of defence. In no case, however, does nature ever give more than one adequate means of
protection to one and the same animal.

Most of the animals that have horns are cloven-hoofed; but the Indian ass, as they call it, is also reported to
be horned, though its hoof is solid.

Again as the body, so far as regards its organs of motion, consists of two distinct parts, the right and the left,
so also and for like reasons the horns of animals are, in the great majority of cases, two in number. Still there
are some that have but a single horn; the Oryx, for instance, and the so-called Indian ass; in the former of
which the hoof is cloven, while in the latter it is solid. In such animals the horn is set in the centre of the
head; for as the middle belongs equally to both extremes, this arrangement is the one that comes nearest to
each side having its own horn.

Again, it would appear consistent with reason that the single horn should go with the solid rather than with
the cloven hoof. For hoof, whether solid or cloven, is of the same nature as horn; so that the two naturally
undergo division simultaneously and in the same animals. Again, since the division of the cloven hoof
depends on deficiency of material, it is but rationally consistent, that nature, when she gave an animal an
excess of material for the hoofs, which thus became solid, should have taken away something from the upper
parts and so made the animal to have but one horn. Rightly too did she act when she chose the head whereon
to set the horns; and AEsop's Momus is beside the mark, when he finds fault with the bull for not having its
horns upon its shoulders. For from this position, says he, they would have delivered their blow with the
greatest force, whereas on the head they occupy the weakest part of the whole body. Momus was but
dull-sighted in making this hostile criticism. For had the horns been set on the shoulders, or had they been set
on any other part than they are, the encumbrance of their weight would have been increased, not only without
any compensating gain whatsoever, but with the disadvantage of impeding many bodily operations. For the
point whence the blows could be delivered with the greatest force was not the only matter to be considered,
but the point also whence they could be delivered with the widest range. But as the bull has no hands and
cannot possibly have its horns on its feet or on its knees, where they would prevent flexion, there remains no
other site for them but the head; and this therefore they necessarily occupy. In this position, moreover, they
are much less in the way of the movements of the body than they would be elsewhere.

ON THE PARTS OF ANIMALS

Deer are the only animals in which the horns are solid throughout, and are also the only animals that cast
them. This casting is not simply advantageous to the deer from the increased lightness which it produces, but,
seeing how heavy the horns are, is a matter of actual necessity.

In all other animals the horns are hollow for a certain distance, and the end alone is solid, this being the part
of use in a blow. At the same time, to prevent even the hollow part from being weak, the horn, though it
grows out of the skin, has a solid piece from the bones fitted into its cavity. For this arrangement is not only
that which makes the horns of the greatest service in fighting, but that which causes them to be as little of an
impediment as possible in the other actions of life.

Such then are the reasons for which horns exist; and such the reasons why they are present in some animals,
absent from others.

Let us now consider the character of the material nature whose necessary results have been made available by
rational nature for a final cause.

In the first place, then, the larger the bulk of animals, the greater is the proportion of corporeal and earthy
matter which they contain. Thus no very small animal is known to have horns, the smallest horned animal
that we are acquainted with being the gazelle. But in all our speculations concerning nature, what we have to
consider is the general rule; for that is natural which applies either universally or generally. And thus when
we say that the largest animals have most earthy matter, we say so because such is the general rule. Now this
earthy matter is used in the animal body to form bone. But in the larger animals there is an excess of it, and
this excess is turned by nature to useful account, being converted into weapons of defence. Part of it
necessarily flows to the upper portion of the body, and this is allotted by her in some cases to the formation of
tusks and teeth, in others to the formation of horns. Thus it is that no animal that has horns has also front teeth
in both jaws, those in the upper jaw being deficient. For nature by subtracting from the teeth adds to the
horns; the nutriment which in most animals goes to the former being here spent on the augmentation of the
latter. Does, it is true, have no horns and yet are equally deficient with the males as regards the teeth. The
reason, however, for this is that they, as much as the males, are naturally horn-bearing animals; but they have
been stripped of their horns, because these would not only be useless to them but actually baneful; whereas
the greater strength of the males causes these organs, though equally useless, to be less of an impediment. In
other animals, where this material is not secreted from the body in the shape of horns, it is used to increase
the size of the teeth; in some cases of all the teeth, in others merely of the tusks, which thus become so long
as to resemble horns projecting from the jaws.

So much, then, of the parts which appertain to the head.

Below the head lies the neck, in such animals as have one. This is the case with those only that have the parts
to which a neck is subservient. These parts are the larynx and what is called the oesophagus. Of these the
former, or larynx, exists for the sake of respiration, being the instrument by which such animals as breathe
inhale and discharge the air. Therefore it is that, when there is no lung, there is also no neck. Of this condition
the Fishes are an example. The other part, or oesophagus, is the channel through which food is conveyed to
the stomach; so that all animals that are without a neck are also without a distinct oesophagus; Such a part is
in fact not required of necessity for nutritive purposes; for it has no action whatsoever on the food. Indeed
there is nothing to prevent the stomach from being placed directly after the mouth. This, however, is quite
impossible in the case of the lung. For there must be some sort of tube common to the two divisions of the
lung, by which — it being bipartite — the breath may be apportioned to their respective bronchi, and thence
pass into the air-pipes; and such an arrangement will be the best for giving perfection to inspiration and

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ON THE PARTS OF ANIMALS

expiration. The organ then concerned in respiration must of necessity be of some length; and this, again,
necessitates there being an oesophagus to unite mouth and stomach. This oesophagus is of a flesh-like
character, and yet admits of extension like a sinew. This latter property is given to it, that it may stretch when
food is introduced; while the flesh-like character is intended to make it soft and yielding, and to prevent it
from being rasped by particles as they pass downwards, and so suffering damage. On the other hand, the
windpipe and the so-called larynx are constructed out of a cartilaginous substance. For they have to serve not
only for respiration, but also for vocal purposes; and an instrument that is to produce sounds must necessarily
be not only smooth but firm. The windpipe lies in front of the oesophagus, although this position causes it to
be some hindrance to the latter in the act of deglutition. For if a morsel of food, fluid or solid, slips into it by
accident, choking and much distress and violent fits of coughing ensue. This must be a matter of
astonishment to any of those who assert that it is by the windpipe that an animal imbibes fluid. For the
consequences just mentioned occur invariably, whenever a particle of food slips in, and are quite obvious.
Indeed on many grounds it is ridiculous to say that this is the channel through which animals imbibe fluid.
For there is no passage leading from the lung to the stomach, such as the oesophagus which we see leading
thither from the mouth. Moreover, when any cause produces sickness and vomiting, it is plain enough when
the fluid is discharged. It is manifest also that fluid, when swallowed, does not pass directly into the bladder
and collect there, but goes first into the stomach. For, when red wine is taken, the dejections of the stomach
are seen to be coloured by its dregs; and such discoloration has been even seen on many occasions inside the
stomach itself, in cases where there have been wounds opening into that organ. However, it is perhaps silly to
be minutely particular in dealing with silly statements such as this.

The windpipe then, owing to its position in front of the oesophagus, is exposed, as we have said, to
annoyance from the food. To obviate this, however, nature has contrived the epiglottis. This part is not found
in all sanguineous animals, but only in such of them as have a lung; nor in all of these, but only in such as at
the same time have their skin covered with hairs, and not either with scaly plates or with feathers. In such
scaly and feathered animals there is no epiglottis, but its office is supplied by the larynx, which closes and
opens, just as in the other case the epiglottis falls down and rises up; rising up during the ingress or egress of
breath, and falling down during the ingestion of food, so as to prevent any particle from slipping into the
windpipe. Should there be the slightest want of accuracy in this movement, or should an inspiration be made
during the ingestion of food, choking and coughing ensue, as already has been noticed. So admirably
contrived, however, is the movement both of the epiglottis and of the tongue, that, while the food is being
ground to a pulp in the mouth, the tongue very rarely gets caught between the teeth; and, while the food is
passing over the epiglottis seldom does a particle of it slip into the windpipe.

The animals which have been mentioned as having no epiglottis owe this deficiency to the dryness of their
flesh and to the hardness of their skin. For an epiglottis made of such materials would not admit of easy
motion. It would, indeed, take a longer time to shut down an epiglottis made of the peculiar flesh of these
animals, and shaped like that of those with hairy skins, than to bring the edges of the windpipe itself into
contact with each other.

Thus much then as to the reason why some animals have an epiglottis while others have none, and thus much
also as to its use. It is a contrivance of nature to remedy the vicious position of the windpipe in front of the
oesophagus. That position is the result of necessity. For it is in the front and centre of the body that the heart
is situated, in which we say is the principle of life and the source of all motion and sensation. (For sensation
and motion are exercised in the direction which we term forwards, and it is on this very relation that the
distinction of before and behind is founded.) But where the heart is, there and surrounding it is the lung. Now
inspiration, which occurs for the sake of the lung and for the sake of the principle which has its seat in the
heart, is effected through the windpipe. Since then the heart must of necessity lie in the very front place of all,
it follows that the larynx also and the windpipe must of necessity lie in front of the oesophagus. For they lead
to the lung and heart, whereas the oesophagus leads to the stomach. And it is a universal law that, as regards
above and below, front and back, right and left, the nobler and more honourable part invariably is placed

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uppermost, in front, and on the right, rather than in the opposite positions, unless some more important object
stands in the way.

We have now dealt with the neck, the oesophagus, and the windpipe, and have next to treat of the viscera.
These are peculiar to sanguineous animals, some of which have all of them, others only a part, while no
bloodless animals have any at all. Democritus then seems to have been mistaken in the notion he formed of
the viscera, if, that is to say, he fancied that the reason why none were discoverable in bloodless animals was
that these animals were too small to allow them to be seen. For, in sanguineous animals, both heart and liver
are visible enough when the body is only just formed, and while it is still extremely small. For these parts are
to be seen in the egg sometimes as early as the third day, being then no bigger than a point; and are visible
also in aborted embryos, while still excessively minute. Moreover, as the external organs are not precisely
alike in all animals, but each creature is provided with such as are suited to its special mode of life and
motion, so is it with the internal parts, these also differing in different animals. Viscera, then, are peculiar to
sanguineous animals; and therefore are each and all formed from sanguineous material, as is plainly to be
seen in the new-born young of these animals. For in such the viscera are more sanguineous, and of greater
bulk in proportion to the body, than at any later period of life, it being in the earliest stage of formation that
the nature of the material and its abundance are most conspicuous. There is a heart, then, in all sanguineous
animals, and the reason for this has already been given. For that sanguineous animals must necessarily have
blood is self-evident. And, as the blood is fluid, it is also a matter of necessity that there shall be a receptacle
for it; and it is apparently to meet this requirement that nature has devised the blood-vessels. These, again,
must necessarily have one primary source. For it is preferable that there shall be one such, when possible,
rather than several. This primary source of the vessels is the heart. For the vessels manifestly issue from it
and do not go through it. Moreover, being as it is homogeneous, it has the character of a blood-vessel. Again
its position is that of a primary or dominating part. For nature, when no other more important purpose stands
in her way, places the more honourable part in the more honourable position; and the heart lies about the
centre of the body, but rather in its upper than its lower half, and also more in front than behind. This is most
evident in the case of man, but even in other animals there is a tendency in the heart to assume a similar
position, in the centre of the necessary part of the body, that is to say of the part which terminates in the vent
for excrement. For the limbs vary in position in different animals, and are not to be counted with the parts
which are necessary for life. For life can be maintained even when they are removed; while it is self-evident
that the addition of them to an animal is not destructive of it.

There are some who say that the vessels commence in the head. In this they are clearly mistaken. For in the
first place, according to their representation, there would be many sources for the vessels, and these scattered;
and secondly, these sources would be in a region that is manifestly cold, as is shown by its intolerance of
chill, whereas the region of the heart is as manifestly hot. Again, as already said, the vessels continue their
course through the other viscera, but no vessel spreads through the heart. From this it is quite evident that the
heart is a part of the vessels and their origin; and for this it is well suited by its structure. For its central part
consists of a dense and hollow substance, and is moreover full of blood, as though the vessels took thence
their origin. It is hollow to serve for the reception of the blood, while its wall is dense, that it may serve to
protect the source of heat. For here, and here alone in all the viscera and indeed in all the body, there is blood
without blood-vessels, the blood elsewhere being always contained within vessels. Nor is this but consistent
with reason. For the blood is conveyed into the vessels from the heart, but none passes into the heart from
without. For in itself it constitutes the origin and fountain, or primary receptacle, of the blood. It is however,
from dissections and from observations on the process of development that the truth of these statements
receives its clearest demonstration. For the heart is the first of all the parts to be formed; and no sooner is it
formed than it contains blood. Moreover, the motions of pain and pleasure, and generally of all sensation,
plainly have their source in the heart, and find in it their ultimate termination. This, indeed, reason would lead

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ON THE PARTS OF ANIMALS

us to expect. For the source must, when, ever possible, be one; and, of all places, the best suited for a source
is the centre. For the centre is one, and is equally or almost equally within reach of every part. Again, as
neither the blood itself, nor yet any part which is bloodless, is endowed with sensation, it is plain that that
part which first has blood, and which holds it as it were in a receptacle, must be the primary source of
sensation. And that this part is the heart is not only a rational inference, but also evident to the senses. For no
sooner is the embryo formed, than its heart is seen in motion as though it were a living creature, and this
before any of the other parts, it being, as thus shown, the starting-point of their nature in all animals that have
blood. A further evidence of the truth of what has been stated is the fact that no sanguineous animal is
without a heart. For the primary source of blood must of necessity be present in them all. It is true that
sanguineous animals not only have a heart but also invariably have a liver. But no one could ever deem the
liver to be the primary organ either of the whole body or of the blood. For the position in which it is placed is
far from being that of a primary or dominating part; and, moreover, in the most perfectly finished animals
there is another part, the spleen, which as it were counterbalances it. Still further, the liver contains no
spacious receptacle in its substance, as does the heart; but its blood is in a vessel as in all the other viscera.
The vessel, moreover, extends through it, and no vessel whatsoever originates in it; for it is from the heart
that all the vessels take their rise. Since then one or other of these two parts must be the central source, and
since it is not the liver which is such, it follows of necessity that it is the heart which is the source of the
blood, as also the primary organ in other respects. For the definitive characteristic of an animal is the
possession of sensation; and the first sensory part is that which first has blood; that is to say is the heart,
which is the source of blood and the first of the parts to contain it.

The apex of the heart is pointed and more solid than the rest of the organ. It lies against the breast, and
entirely in the anterior part of the body, in order to prevent that region from getting chilled. For in all animals
there is comparatively little flesh over the breast, whereas there is a more abundant covering of that substance
on the posterior surface, so that the heat has in the back a sufficient amount of protection. In all animals but
man the heart is placed in the centre of the pectoral region; but in man it inclines a little towards the left, so
that it may counterbalance the chilliness of that side. For the left side is colder in man, as compared with the
right, than in any other animal. It has been stated in an earlier treatise that even in fishes the heart holds the
same position as in other animals; and the reason has been given why it appears not to do so. The apex of the
heart, it is true, is in them turned towards the head, but this in fishes is the front aspect, for it is the direction
in which their motion occurs.

The heart again is abundantly supplied with sinews, as might reasonably be expected. For the motions of the
body commence from the heart, and are brought about by traction and relaxation. The heart therefore, which,
as already said,' as it were a living creature inside its possessor, requires some such subservient and
strengthening parts.

In no animals does the heart contain a bone, certainly in none of those that we have ourselves inspected, with
the exception of the horse and a certain kind of ox. In these exceptional cases the heart, owing to its large
bulk, is provided with a bone as a support; just as the bones serve as supports for the body generally.

In animals of great size the heart has three cavities; in smaller animals it has two; and in all has at least one,
for, as already stated, there must be some place in the heart to serve as a receptacle for the first blood; which,
as has been mentioned more than once, is formed in this organ. But inasmuch as the main blood-vessels are
two in number, namely the so-called great vessel and the aorta, each of which is the origin of other vessels;
inasmuch, moreover, as these two vessels present differences, hereafter to be discussed, when compared with
each other, it is of advantage that they also shall themselves have distinct origins. This advantage will be
obtained if each side have its own blood, and the blood of one side be kept separate from that of the other.
For this reason the heart, whenever it is possible, has two receptacles. And this possibility exists in the case of
large animals, for in them the heart, as the body generally, is of large size. Again it is still better that there
shall be three cavities, so that the middle and odd one may serve as a centre common to both sides. But this

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ON THE PARTS OF ANIMALS

requires the heart to be of greater magnitude, so that it is only in the largest hearts that there are three cavities.

Of these three cavities it is the right that has the most abundant and the hottest blood, and this explains why
the limbs also on the right side of the body are warmer than those on the left. The left cavity has the least
blood of all, and the coldest; while in the middle cavity the blood, as regards quantity and heat, is
intermediate to the other two, being however of purer quality than either. For it behoves the supreme part to
be as tranquil as possible, and this tranquillity can be ensured by the blood being pure, and of moderate
amount and warmth.

In the heart of animals there is also a kind of joint-like division, something like the sutures of the skull. This
is not, however, attributable to the heart being formed by the union of several parts into a compound whole,
but is rather, as already said, the result of a joint-like division. These jointings are most distinct in animals of
keen sensibility, and less so in those that are of duller feeling, in swine for instance. Different hearts differ
also from each other in their sizes, and in their degrees of firmness; and these differences somehow extend
their influence to the temperaments of the animals. For in animals of low sensibility the heart is hard and
dense in texture, while it is softer in such as are endowed with keener feeling. So also when the heart is of
large size the animal is timorous, while it is more courageous if the organ be smaller and of moderate bulk.
For in the former the bodily affection which results from terror already pre-exists; for the bulk of the heart is
out of all proportion to the animal's heat, which being small is reduced to insignificance in the large space,
and thus the blood is made colder than it would otherwise be.

The heart is of large size in the hare, the deer, the mouse, the hyena, the ass, the leopard, the marten, and in
pretty nearly all other animals that either are manifestly timorous, or betray their cowardice by their
spitefulness.

What has been said of the heart as a whole is no less true of its cavities and of the blood-vessels; these also if
of large size being cold. For just as a fire of equal size gives less heat in a large room than in a small one, so
also does the heat in a large cavity or a large blood-vessel, that is in a large receptacle, have less effect than
in a small one. Moreover, all hot bodies are cooled by motions external to themselves, and the more spacious
the cavities and vessels are, the greater the amount of spirit they contain, and the more potent its action. Thus
it is that no animal that has large cavities in its heart, or large blood-vessels, is ever fat, the vessels being
indistinct and the cavities small in all or most fat animals.

The heart again is the only one of the viscera, and indeed the only part of the body, that is unable to tolerate
any serious affection. This is but what might reasonably be expected. For, if the primary or dominant part be
diseased, there is nothing from which the other parts which depend upon it can derive succour. A proof that
the heart is thus unable to tolerate any morbid affection is furnished by the fact that in no sacrificial victim
has it ever been seen to be affected with those diseases that are observable in the other viscera. For the
kidneys are frequently found to be full of stones, and growths, and small abscesses, as also are the liver, the
lung, and more than all the spleen. There are also many other morbid conditions which are seen to occur in
these parts, those which are least liable to such being the portion of the lung which is close to the windpipe,
and the portion of the liver which lies about the junction with the great blood-vessel. This again admits of a
rational explanation. For it is in these parts that the lung and liver are most closely in communion with the
heart. On the other hand, when animals die not by sacrifice but from disease, and from affections such as are
mentioned above, they are found on dissection to have morbid affections of the heart.

Thus much of the heart, its nature, and the end and cause of its existence in such animals as have it.

ON THE PARTS OF ANIMALS

In due sequence we have next to discuss the blood-vessels, that is to say the great vessel and the aorta. For it
is into these two that the blood first passes when it quits the heart; and all the other vessels are but offshoots
from them. Now that these vessels exist on account of the blood has already been stated. For every fluid
requires a receptacle, and in the case of the blood the vessels are that receptacle. Let us now explain why
these vessels are two, and why they spring from one single source, and extend throughout the whole body.

The reason, then, why these two vessels coalesce into one centre, and spring from one source, is that the
sensory soul is in all animals actually one; and this one-ness of the sensory soul determines a corresponding
one-ness of the part in which it primarily abides. In sanguineous animals this one-ness is not only actual but
potential, whereas in some bloodless animals it is only actual. Where, however, the sensory soul is lodged,
there also and in the selfsame place must necessarily be the source of heat; and, again, where this is there also
must be the source of the blood, seeing that it thence derives its warmth and fluidity. Thus, then, in the
oneness of the part in which is lodged the prime source of sensation and of heat is involved the one-ness of
the source in which the blood originates; and this, again, explains why the blood-vessels have one common
starting-point.

The vessels, again, are two, because the body of every sanguineous animal that is capable of locomotion is
bilateral; for in all such animals there is a distinguishable before and behind, a right and left, an above and
below. Now as the front is more honourable and of higher supremacy than the hinder aspect, so also and in
like degree is the great vessel superior to the aorta. For the great vessel is placed in front, while the aorta is
behind; the former again is plainly visible in all sanguineous animals, while the latter is in some indistinct
and in some not discernible at all.

Lastly, the reason for the vessels being distributed throughout the entire body is that in them, or in parts
analogous to them, is contained the blood, or the fluid which in bloodless animals takes the place of blood,
and that the blood or analogous fluid is the material from which the whole body is made. Now as to the
manner in which animals are nourished, and as to the source from which they obtain nutriment and as to the
way in which they absorb this from the stomach, these are matters which may be more suitably considered
and explained in the treatise on Generation. But inasmuch as the parts are, as already said, formed out of the
blood, it is but rational that the flow of the blood should extend, as it does, throughout the whole of the body.
For since each part is formed of blood, each must have blood about and in its substance.

To give an illustration of this. The water-courses in gardens are so constructed as to distribute water from
one single source or fount into numerous channels, which divide and subdivide so as to convey it to all parts;
and, again, in house-building stones are thrown down along the whole ground-plan of the foundation walls;
because the garden-plants in the one case grow at the expense of the water, and the foundation walls in the
other are built out of the stones. Now just after the same fashion has nature laid down channels for the
conveyance of the blood throughout the whole body, because this blood is the material out of which the
whole fabric is made. This becomes very evident in bodies that have undergone great emaciation. For in such
there is nothing to be seen but the blood-vessels; just as when fig-leaves or vine-leaves or the like have
dried up, there is nothing left of them but their vessels. The explanation of this is that the blood, or fluid
which takes its place, is potentially body and flesh, or substance analogous to flesh. Now just as in irrigation
the largest dykes are permanent, while the smallest are soon filled up with mud and disappear, again to
become visible when the deposit of mud ceases; so also do the largest blood-vessels remain permanently
open, while the smallest are converted actually into flesh, though potentially they are no whit less vessels
than before. This too explains why, so long as the flesh of an animal is in its integrity, blood will flow from
any part of it whatsoever that is cut, though no vessel, however small, be visible in it. Yet there can be no
blood, unless there be a blood-vessel. The vessels then are there, but are invisible owing to their being

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ON THE PARTS OF ANIMALS

clogged up, just as the dykes for irrigation are invisible until they have been cleared of mud.

As the blood-vessels advance, they become gradually smaller and smaller, until at last their tubes are too fine
to admit the blood. This fluid can therefore no longer find its way through them, though they still give
passage to the humour which we call sweat; and especially so when the body is heated, and the mouths of the
small vessels are dilated. Instances, indeed, are not unknown of persons who in consequence of a cachectic
state have secreted sweat that resembled blood, their body having become loose and flabby, and their blood
watery, owing to the heat in the small vessels having been too scanty for its concoction. For, as was before
said, every compound of earth and water-and both nutriment and blood are such-becomes thicker from
concoction. The inability of the heat to effect concoction may be due either to its being absolutely small in
amount, or to its being small in proportion to the quantity of food, when this has been taken excess. This
excess again may be of two kinds, either quantitative or qualitative; for all substances are not equally
amenable to concoction.

The widest passages in the body are of all parts the most liable to haemorrhage; so that bleeding occurs not
infrequently from the nostrils, the gums, and the fundament, occasionally also from the mouth. Such
haemorrhages are of a passive kind, and not violent as are those from the windpipe.

The great vessel and the aorta, which above lie somewhat apart, lower down exchange positions, and by so
doing give compactness to the body. For when they reach the point where the legs diverge, they each split
into two, and the great vessel passes from the front to the rear, and the aorta from the rear to the front. By this
they contribute to the unity of the whole fabric. For as in plaited work the parts hold more firmly together
because of the interweaving, so also by the interchange of position between the blood-vessels are the anterior
and posterior parts of the body more closely knit together. A similar exchange of position occurs also in the
upper part of the body, between the vessels that have issued from the heart. The details however of the mutual
relations of the different vessels must be looked for in the treatises on Anatomy and the Researches
concerning Animals.

So much, then, as concerns the heart and the blood-vessels. We must now pass on to the other viscera and
apply the same method of inquiry to them.

The lung, then, is an organ found in all the animals of a certain class, because they live on land. For there
must of necessity be some means or other of tempering the heat of the body; and in sanguineous animals, as
they are of an especially hot nature, the cooling agency must be external, whereas in the bloodless kinds the
innate spirit is sufficient of itself for the purpose. The external cooling agent must be either air or water. In
fishes the agent is water. Fishes therefore never have a lung, but have gills in its place, as was stated in the
treatise on Respiration. But animals that breathe are cooled by air. These therefore are all provided with a
lung.

All land animals breathe, and even some water animals, such as the whale, the dolphin, and all the spouting
Cetacea. For many animals lie half-way between terrestrial and aquatic; some that are terrestrial and that
inspire air being nevertheless of such a bodily constitution that they abide for the most time in the water; and
some that are aquatic partaking so largely of the land character, that respiration constitutes for them the man
condition of life.

The organ of respiration is the lung. This derives its motion from the heart; but it is its own large size and
spongy texture that affords amplitude of space for entrance of the breath. For when the lung rises up the
breath streams in, and is again expelled when the lung collapses. It has been said that the lung exists as a

6 40

ON THE PARTS OF ANIMALS

provision to meet the jumping of the heart. But this is out of the question. For man is practically the only
animal whose heart presents this phenomenon of jumping, inasmuch as he alone is influenced by hope and
anticipation of the future. Moreover, in most animals the lung is separated from the heart by a considerable
interval and lies above it, so that it can contribute nothing to mitigate any jumping.

The lung differs much in different animals. For in some it is of large size and contains blood; while in others
it is smaller and of spongy texture. In the vivipara it is large and rich in blood, because of their natural heat;
while in the ovipara it is small and dry but capable of expanding to a vast extent when inflated. Among
terrestrial animals, the oviparous quadrupeds, such as lizards, tortoises, and the like, have this kind of lung;
and, among inhabitants of the air, the animals known as birds. For in all these the lung is spongy, and like
foam. For it is membranous and collapses from a large bulk to a small one, as does foam when it runs
together. In this too lies the explanation of the fact that these animals are little liable to thirst and drink but
sparingly, and that they are able to remain for a considerable time under water. For, inasmuch as they have
but little heat, the very motion of the lung, airlike and void, suffices by itself to cool them for a considerable
period.

These animals, speaking generally, are also distinguished from others by their smaller bulk. For heat
promotes growth, and abundance of blood is a sure indication of heat. Heat, again, tends to make the body
erect; and thus it is that man is the most erect of animals, and the vivipara more erect than other quadrupeds.
For no viviparous animal, be it apodous or be it possessed of feet, is so given to creep into holes as are the
ovipara.

The lung, then, exists for respiration; and this is its universal office; but in one order of animals it is bloodless
and has the structure described above, to suit the special requirements There is, however, no one term to
denote all animals that have a lung; no designation, that is, like the term Bird, applicable to the whole of a
certain class. Yet the possession of a lung is a part of their essence, just as much as the presence of certain
characters constitutes the essence of a bird.

Of the viscera some appear to be single, as the heart and lung; others to be double, as the kidneys; while of a
third kind it is doubtful in which class they should be reckoned. For the liver and the spleen would seem to lie
half-way between the single and the double organs. For they may be regarded either as constituting each a
single organ, or as a pair of organs resembling each other in character.

In reality, however, all the organs are double. The reason for this is that the body itself is double, consisting
of two halves, which are however combined together under one supreme centre. For there is an upper and a
lower half, a front and a rear, a right side and a left.

This explains why it is that even the brain and the several organs of sense tend in all animals to consist of two
parts; and the same explanation applies to the heart with its cavities. The lung again in Ovipara is divided to
such an extent that these animals look as though they had actually two lungs. As to the kidneys, no one can
overlook their double character. But when we come to the liver and the spleen, any one might fairly be in
doubt. The reason of this is, that, in animals that necessarily have a spleen, this organ is such that it might be
taken for a kind of bastard liver; while in those in which a spleen is not an actual necessity but is merely
present, as it were, by way of token, in an extremely minute form, the liver plainly consists of two parts; of
which the larger tends to lie on the right side and the smaller on the left. Not but what there are some even of
the Ovipara in which this condition is comparatively indistinctly marked; while, on the other hand, there are
some Vivipara in which the liver is manifestly divided into two parts. Examples of such division are
furnished by the hares of certain regions, which have the appearance of having two livers, and by the

7 41

ON THE PARTS OF ANIMALS

cartilaginous and some other fishes.

It is the position of the liver on the right side of the body that is the main cause for the formation of the
spleen; the existence of which thus becomes to a certain extent a matter of necessity in all animals, though
not of very stringent necessity.

The reason, then, why the viscera are bilateral is, as we have said, that there are two sides to the body, a right
and a left. For each of these sides aims at similarity with the other, and so likewise do their several viscera;
and as the sides, though dual, are knit together into unity, so also do the viscera tend to be bilateral and yet
one by unity of constitution.

Those viscera which lie below the diaphragm exist one and all on account of the blood-vessels; serving as a
bond, by which these vessels, while floating freely, are yet held in connexion with the body. For the vessels
give off branches which run to the body through the outstretched structures, like so many anchorlines thrown
out from a ship. The great vessel sends such branches to the liver and the spleen; and these viscera-the liver
and spleen on either side with the kidneys behind-attach the great vessel to the body with the firmness of
nails. The aorta sends similar branches to each kidney, but none to the liver or spleen.

These viscera, then, contribute in this manner to the compactness of the animal body. The liver and spleen
assist, moreover, in the concoction of the food; for both are of a hot character, owing to the blood which they
contain. The kidneys, on the other hand, take part in the separation of the excretion which flows into the
bladder.

The heart then and the liver are essential constituents of every animal; the liver that it may effect concoction,
the heart that it may lodge the central source of heat. For some part or other there must be which, like a
hearth, shall hold the kindling fire; and this part must be well protected, seeing that it is, as it were, the citadel
of the body.

All sanguineous animals, then, need these two parts; and this explains why these two viscera, and these two
alone, are invariably found in them all. In such of them, however, as breathe, there is also as invariably a
third, namely the lung. The spleen, on the other hand, is not invariably present; and, in those animals that
have it, is only present of necessity in the same sense as the excretions of the belly and of the bladder are
necessary, in the sense, that is, of being an inevitable concomitant. Therefore it is that in some animals the
spleen is but scantily developed as regards size. This, for instance, is the case in such feathered animals as
have a hot stomach. Such are the pigeon, the hawk, and the kite. It is the case also in oviparous quadrupeds,
where the spleen is excessively minute, and in many of the scaly fishes. These same animals are also without
a bladder, because the loose texture of their flesh allows the residual fluid to pass through and to be applied to
the formation of feathers and scales. For the spleen attracts the residual humours from the stomach, and
owing to its bloodlike character is enabled to assist in their concoction. Should, however, this residual fluid
be too abundant, or the heat of the spleen be too scanty, the body becomes sickly from over-repletion with
nutriment. Often, too, when the spleen is affected by disease, the belly becomes hard owing to the reflux into
it of the fluid; just as happens to those who form too much urine, for they also are liable to a similar diversion
of the fluids into the belly. But in those animals that have but little superfluous fluid to excrete, such as birds
and fishes, the spleen is never large, and in some exists no more than by way of token. So also in the
oviparous quadrupeds it is small, compact, and like a kidney. For their lung is spongy, and they drink but
little, and such superfluous fluid as they have is applied to the growth of the body and the formation of scaly
plates, just as in birds it is applied to the formation of feathers.

On the other hand, in such animals as have a bladder, and whose lung contains blood, the spleen is watery,
both for the reason already mentioned, and also because the left side of the body is more watery and colder
than the right. For each of two contraries has been so placed as to go together with that which is akin to it in

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ON THE PARTS OF ANIMALS

another pair of contraries. Thus right and left, hot and cold, are pairs of contraries; and right is conjoined with
hot, after the manner described, and left with cold.

The kidneys when they are present exist not of actual necessity, but as matters of greater finish and
perfection. For by their special character they are suited to serve in the excretion of the fluid which collects in
the bladder. In animals therefore where this fluid is very abundantly formed, their presence enables the
bladder to perform its proper office with greater perfection.

Since then both kidneys and bladder exist in animals for one and the same function, we must next treat of the
bladder, though in so doing we disregard the due order of succession in which the parts should be
enumerated. For not a word has yet been said of the midriff, which is one of the parts that environ the viscera
and therefore has to be considered with them.

It is not every animal that has a bladder; those only being apparently intended by nature to have one, whose
lung contains blood. To such it was but reasonable that she should give this part. For the superabundance in
their lung of its natural constituents causes them to be the thirstiest of animals, and makes them require a
more than ordinary quantity not merely of solid but also of liquid nutriment. This increased consumption
necessarily entails the production of an increased amount of residue; which thus becomes too abundant to be
concocted by the stomach and excreted with its own residual matter. The residual fluid must therefore of
necessity have a receptacle of its own; and thus it comes to pass that all animals whose lung contains blood
are provided with a bladder. Those animals, on the other hand, that are without a lung of this character, and
that either drink but sparingly owing to their lung being of a spongy texture, or never imbibe fluid at all for
drinking's sake but only as nutriment, insects for instance and fishes, and that are moreover clad with feathers
or scales or scaly plates-all these animals, owing to the small amount of fluid which they imbibe, and owing
also to such residue as there may be being converted into feathers and the like, are invariably without a
bladder. The Tortoises, which are comprised among animals with scaly plates, form the only exception; and
this is merely due to the imperfect development of their natural conformation; the explanation of the matter
being that in the sea-tortoises the lung is flesh-like and contains blood, resembling the lung of the ox, and
that in the land-tortoises it is of disproportionately large size. Moreover, inasmuch as the covering which
invests them is dense and shell-like, so that the moisture cannot exhale through the porous flesh, as it does in
birds and in snakes and other animals with scaly plates, such an amount of secretion is formed that some
special part is required to receive and hold it. This then is the reason why these animals, alone of their kind,
have a bladder, the sea-tortoise a large one, the land-tortoises an extremely small one.

What has been said of the bladder is equally true of the kidneys. For these also are wanting in all animals that
are clad with feathers or with scales or with scale-like plates; the sea and land tortoises forming the only
exception. In some of the birds, however, there are flattened kidney like bodies, as though the flesh allotted to
the formation of the kidneys, unable to find one single place of sufficient size, had been scattered over
several.

The Emys has neither bladder nor kidneys. For the softness of its shell allows of the ready transpiration of
fluid; and for this reason neither of the organs mentioned exists in this animal. All other animals, however,
whose lung contains blood are, as before said, provided with kidneys. For nature uses these organs for two
separate purposes, namely for the excretion of the residual fluid, and to subserve the blood-vessels, a channel
leading to them from the great vessel.

ON THE PARTS OF ANIMALS

In the centre of the kidney is a cavity of variable size. This is the case in all animals, excepting the seal. The
kidneys of this animal are more solid than those of any other, and in form resemble the kidneys of the ox. The
human kidneys are of similar shape; being as it were made up of numerous small kidneys, and not presenting
one unbroken surface like the kidneys of sheep and other quadrupeds. For this reason, should the kidneys of a
man be once attacked by disease, the malady is not easily expelled. For it is as though many kidneys were
diseased and not merely one; which naturally enhances the difficulties of a cure.

The duct which runs to the kidney from the great vessel does not terminate in the central cavity, but is
expended on the substance of the organ, so that there is no blood in the cavity, nor is any coagulum found
there after death. A pair of stout ducts, void of blood, run, one from the cavity of each kidney, to the bladder;
and other ducts, strong and continuous, lead into the kidneys from the aorta. The purpose of this arrangement
is to allow the superfluous fluid to pass from the blood-vessel into the kidney, and the resulting renal
excretion to collect by the percolation of the fluid through the solid substance of the organ, in its centre,
where as a general rule there is a cavity. (This by the way explains why the kidney is the most ill-savoured of
all the viscera.) From the central cavity the fluid is discharged into the bladder by the ducts that have been
mentioned, having already assumed in great degree the character of excremental residue. The bladder is as it
were moored to the kidneys; for, as already has been stated, it is attached to them by strong ducts. These then
are the purposes for which the kidneys exist, and such the functions of these organs.

In all animals that have kidneys, that on the right is placed higher than that on the left. For inasmuch as
motion commences from the right, and the organs on this side are in consequence stronger than those on the
left, they must all push upwards in advance of their opposite fellows; as may be seen in the fact that men even
raise the right eyebrow more than the left, and that the former is more arched than the latter. The right kidney
being thus drawn upwards is in all animals brought into contact with the liver; for the liver lies on the right
side.

Of all the viscera the kidneys are those that have the most fat. This is in the first place the result of necessity,
because the kidneys are the parts through which the residual matters percolate. For the blood which is left
behind after this excretion, being of pure quality, is of easy concoction, and the final result of thorough
blood-concoction is lard and suet. For just as a certain amount of fire is left in the ashes of solid substances
after combustion, so also does a remnant of the heat that has been developed remain in fluids after
concoction; and this is the reason why oily matter is light, and floats on the surface of other fluids. The fat is
not formed in the kidneys themselves, the density of their substance forbidding this, but is deposited about
their external surface. It consists of lard or of suet, according as the animal's fat is of the former or latter
character. The difference between these two kinds of fat has already been set forth in other passages. The
formation, then, of fat in the kidneys is the result of necessity; being, as explained, a consequence of the
necessary conditions which accompany the possession of such organs. But at the same time the fat has a final
cause, namely to ensure the safety of the kidneys, and to maintain their natural heat. For placed, as these
organs are, close to the surface, they require a greater supply of heat than other parts. For while the back is
thickly covered with flesh, so as to form a shield for the heart and neighbouring viscera, the loins, in
accordance with a rule that applies to all bendings, are destitute of flesh; and fat is therefore formed as a
substitute for it, so that the kidneys may not be without protection. The kidneys, moreover, by being fat are
the better enabled to secrete and concoct their fluid; for fat is hot, and it is heat that effects concoction.

Such, then, are the reasons why the kidneys are fat. But in all animals the right kidney is less fat than its
fellow. The reason for this is, that the parts on the right side are naturally more solid and more suited for
motion than those on the left. But motion is antagonistic to fat, for it tends to melt it.

Animals then, as a general rule, derive advantage from their kidneys being fat; and the fat is often very
abundant and extends over the whole of these organs. But, should the like occur in the sheep, death ensues.
Be its kidneys, however, as fat as they may, they are never so fat but that some part, if not in both at any rate

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ON THE PARTS OF ANIMALS

in the right one, is left free. The reason why sheep are the only animals that suffer in this manner, or suffer
more than others, is that in animals whose fat is composed of lard this is of fluid consistency, so that there is
not the same chance in their case of wind getting shut in and causing mischief. But it is to such an enclosure
of wind that rot is due. And thus even in men, though it is beneficial to them to have fat kidneys, yet should
these organs become over-fat and diseased, deadly pains ensue. As to those animals whose fat consists of
suet, in none is the suet so dense as in the sheep, neither is it nearly so abundant; for of all animals there is
none in which the kidneys become so soon gorged with fat as in the sheep. Rot, then, is produced by the
moisture and the wind getting shut up in the kidneys, and is a malady that carries off sheep with great
rapidity. For the disease forthwith reaches the heart, passing thither by the aorta and the great vessel, the
ducts which connect these with the kidneys being of unbroken continuity.

We have now dealt with the heart and the lung, as also with the liver, spleen, and kidneys. The latter are
separated from the former by the midriff or, as some call it, the Phrenes. This divides off the heart and lung,
and, as already said, is called Phrenes in sanguineous animals, all of which have a midriff, just as they all
have a heart and a liver. For they require a midriff to divide the region of the heart from the region of the
stomach, so that the centre wherein abides the sensory soul may be undisturbed, and not be overwhelmed,
directly food is taken, by its up-steaming vapour and by the abundance of heat then superinduced. For it was
to guard against this that nature made a division, constructing the midriff as a kind of partition-wall and
fence, and so separated the nobler from the less noble parts, in all cases where a separation of upper from
lower is possible. For the upper part is the more honourable, and is that for the sake of which the rest exists;
while the lower part exists for the sake of the upper and constitutes the necessary element in the body,
inasmuch as it is the recipient of the food.

That portion of the midriff which is near the ribs is fleshier and stronger than the rest, but the central part has
more of a membranous character; for this structure conduces best to its strength and its extensibility. Now
that the midriff, which is a kind of outgrowth from the sides of the thorax, acts as a screen to prevent heat
mounting up from below, is shown by what happens, should it, owing to its proximity to the stomach, attract
thence the hot and residual fluid. For when this occurs there ensues forthwith a marked disturbance of
intellect and of sensation. It is indeed because of this that the midriff is called Phrenes, as though it had some
share in the process of thinking (Phronein). in reality, however, it has no part whatsoever itself in the matter,
but, lying in close proximity to organs that have, it brings about the manifest changes of intelligence in
question by acting upon them. This too explains why its central part is thin. For though this is in some
measure the result of necessity, inasmuch as those portions of the fleshy whole which lie nearest to the ribs
must necessarily be fleshier than the rest, yet besides this there is a final cause, namely to give it as small a
proportion of humour as possible; for, had it been made of flesh throughout, it would have been more likely
to attract and hold a large amount of this. That heating of it affects sensation rapidly and in a notable manner
is shown by the phenomena of laughing. For when men are tickled they are quickly set a-laughing, because
the motion quickly reaches this part, and heating it though but slightly nevertheless manifestly so disturbs the
mental action as to occasion movements that are independent of the will. That man alone is affected by
tickling is due firstly to the delicacy of his skin, and secondly to his being the only animal that laughs. For to
be tickled is to be set in laughter, the laughter being produced such a motion as mentioned of the region of the
armpit.

It is said also that when men in battle are wounded anywhere near the midriff, they are seen to laugh, owing
to the heat produced by the wound. This may possibly be the case. At any rate it is a statement made by much
more credible persons than those who tell the story of the human head, how it speaks after it is cut off. For so
some assert, and even call in Homer to support them, representing him as alluding to this when he wrote, 'His
head still speaking rolled into the dust,' instead of 'The head of the speaker'. So fully was the possibility of

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ON THE PARTS OF ANIMALS

such an occurrence accepted in Caria, that one of that country was actually brought to trial under the
following circumstances. The priest of Zeus Hoplosmios had been murdered; but as yet it had not been
ascertained who was the assassin; when certain persons asserted that they had heard the murdered man's
head, which had been severed from the body, repeat several times the words, 'Cercidas slew man on mam.'
Search was thereupon made and a man of those parts who bore the name of Cercidas hunted out and put upon
his trial. But it is impossible that any one should utter a word when the windpipe is severed and no motion
any longer derived from the lung. Moreover, among the Barbarians, where heads are chopped off with great
rapidity, nothing of the kind has ever yet occurred. Why, again, does not the like occur in the case of other
animals than man? For that none of them should laugh, when their midriff is wounded, is but what one would
expect; for no animal but man ever laughs. So, too, there is nothing irrational in supposing that the trunk may
run forwards to a certain distance after the head has been cut seeing that bloodless animals at any rate can
live, and that for a considerable time, after decapitation, as has been set forth and explained in other passages.

The purposes, then, for which the viscera severally exist have now been stated. It is of necessity upon the
inner terminations of the vessels that they are developed; for humour, and that of a bloody character, cannot
but exude at these points, and it is of this, solidified and coagulated, that the substance of the viscera is
formed. Thus they are of a bloody character, and in substance resemble each other while they differ from
other parts.

The viscera are enclosed each in a membrane. For they require some covering to protect them from injury,
and require, moreover, that this covering shall be light. To such requirements membrane is well adapted; for
it is close in texture so as to form a good protection, destitute of flesh so as neither to attract humour nor
retain it, and thin so as to be light and not add to the weight of the body. Of the membranes those are the
stoutest and strongest which invest the heart and the brain; as is but consistent with reason. For these are the
parts which require most protection, seeing that they are the main governing powers of life, and that it is to
governing powers that guard is due.

Some animals have all the viscera that have been enumerated; others have only some of them. In what kind of
animals this latter is the case, and what is the explanation, has already been stated. Moreover, the self-same
viscera present differences in different possessors. For the heart is not precisely alike in all animals that have
one; nor, in fact, is any viscus whatsoever. Thus the liver is in some animals split into several parts, while in
others it is comparatively undivided. Such differences in its form present themselves even among those
sanguineous animals that are viviparous, but are more marked in fishes and in the oviparous quadrupeds, and
this whether we compare them with each other or with the Vivipara. As for birds, their liver very nearly
resembles that of the Vivipara; for in them, as in these, it is of a pure and blood-like colour. The reason of
this is that the body in both these classes of animals admits of the freest exhalation, so that the amount of foul
residual matter within is but small. Hence it is that some of the Vivipara are without any gall-bladder at all.
For the liver takes a large share in maintaining the purity of composition and the healthiness of the body. For
these are conditions that depend finally and in the main upon the blood, and there is more blood in the liver
than in any of the other viscera, the heart only excepted. On the other hand, the liver of oviparous quadrupeds
and fishes inclines, as a rule, to a yellow hue, and there are even some of them in which it is entirely of this
bad colour, in accordance with the bad composition of their bodies generally. Such, for instance, is the case in
the toad, the tortoise, and other similar animals.

The spleen, again, varies in different animals. For in those that have horns and cloven hoofs, such as the goat,
the sheep, and the like, it is of a rounded form; excepting when increased size has caused some part of it to

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ON THE PARTS OF ANIMALS

extend its growth longitudinally, as has happened in the case of the ox. On the other hand, it is elongated in
all polydactylous animals. Such, for instance, is the case in the pig, in man, and in the dog. While in animals
with solid hoofs it is of a form intermediate to these two, being broad in one part, narrow in another. Such, for
example, is its shape in the horse, the mule, and the ass.

The viscera differ from the flesh not only in the turgid aspect of their substance, but also in position; for they
lie within the body, whereas the flesh is placed on the outside. The explanation of this is that these parts
partake of the character of blood-vessels, and that while the former exist for the sake of the vessels, the latter
cannot exist without them.

Below the midriff lies the stomach, placed at the end of the oesophagus when there is one, and in immediate
contiguity with the mouth when the oesophagus is wanting. Continuous with this stomach is what is called
the gut. These parts are present in all animals, for reasons that are self-evident. For it is a matter of necessity
that an animal shall receive the incoming food; and necessary also that it shall discharge the same when its
goodness is exhausted. This residual matter, again, must not occupy the same place as the yet unconcocted
nutriment. For as the ingress of food and the discharge of the residue occur at distinct periods, so also must
they necessarily occur in distinct places. Thus there must be one receptacle for the ingoing food and another
for the useless residue, and between these, therefore, a part in which the change from one condition to the
other may be effected. These, however, are matters which will be more suitably set forth when we come to
deal with Generation and Nutrition. What we have at present to consider are the variations presented by the
stomach and its subsidiary parts. For neither in size nor in shape are these parts uniformly alike in all animals.
Thus the stomach is single in all such sanguineous and viviparous animals as have teeth in front of both jaws.
It is single therefore in all the polydactylous kinds, such as man, dog, lion, and the rest; in all the
solid-hoofed animals also, such as horse, mule, ass; and in all those which, like the pig, though their hoof is
cloven, yet have front teeth in both jaws. When, however, an animal is of large size, and feeds on substances
of so thorny and ligneous a character as to be difficult of concoction, it may in consequence have several
stomachs, as for instance is the case with the camel. A similar multiplicity of stomachs exists also in the
horned animals; the reason being that horn-bearing animals have no front teeth in the upper jaw. The camel
also, though it has no horns, is yet without upper front teeth. The explanation of this is that it is more essential
for the camel to have a multiple stomach than to have these teeth. Its stomach, then, is constructed like that of
animals without upper front teeth, and, its dental arrangements being such as to match its stomach, the teeth
in question are wanting. They would indeed be of no service. Its food, moreover, being of a thorny character,
and its tongue necessarily made of a fleshy substance, nature uses the earthy matter which is saved from the
teeth to give hardness to the palate. The camel ruminates like the horned animals, because its multiple
stomach resembles theirs. For all animals that have horns, the sheep for instance, the ox, the goat, the deer,
and the like, have several stomachs. For since the mouth, owing to its lack of teeth, only imperfectly performs
its office as regards the food, this multiplicity of stomachs is intended to make up for its shortcomings; the
several cavities receiving the food one from the other in succession; the first taking the unreduced substances,
the second the same when somewhat reduced, the third when reduction is complete, and the fourth when the
whole has become a smooth pulp. Such is the reason why there is this multiplicity of parts and cavities in
animals with such dentition. The names given to the several cavities are the paunch, the honeycomb bag, the
manyplies, and the reed. How these parts are related to each other, in position and in shape, must be looked
for in the treatises on Anatomy and the Researches concerning Animals.

Birds also present variations in the part which acts as a recipient of the food; and the reason for these
variations is the same as in the animals just mentioned. For here again it is because the mouth fails to perform

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ON THE PARTS OF ANIMALS

its office and fails even more completely-for birds have no teeth at all, nor any instrument whatsoever with
which to comminute or grind down their food-it is, I say, because of this, that in some of them what is called
the crop precedes the stomach and does the work of the mouth; while in others the oesophagus is either wide
throughout or a part of it bulges just before it enters the stomach, so as to form a preparatory store-house for
the unreduced food; or the stomach itself has a protuberance in some part, or is strong and fleshy, so as to be
able to store up the food for a considerable period and to concoct it, in spite of its not having been ground into
a pulp. For nature retrieves the inefficiency of the mouth by increasing the efficiency and heat of the stomach.
Other birds there are, such, namely, as have long legs and live in marshes, that have none of these provisions,
but merely an elongated oesophagus. The explanation of this is to be found in the moist character of their
food. For all these birds feed on substances easy of reduction, and their food being moist and not requiring
much concoction, their digestive cavities are of a corresponding character.

Fishes are provided with teeth, which in almost all of them are of the sharp interfitting kind. For there is but
one small section in which it is otherwise. Of these the fish called Scarus (Parrot-fish) is an example. And
this is probably the reason why this fish apparently ruminates, though no other fishes do so. For those horned
animals that have no front teeth in the upper jaw also ruminate.

In fishes the teeth are all sharp; so that these animals can divide their food, though imperfectly. For it is
impossible for a fish to linger or spend time in the act of mastication, and therefore they have no teeth that are
flat or suitable for grinding; for such teeth would be to no purpose. The oesophagus again in some fishes is
entirely wanting, and in the rest is but short. In order, however, to facilitate the concoction of the food, some
of them, as the Cestreus (mullet), have a fleshy stomach resembling that of a bird; while most of them have
numerous processes close against the stomach, to serve as a sort of antechamber in which the food may be
stored up and undergo putrefaction and concoction. There is contrast between fishes and birds in the position
of these processes. For in fishes they are placed close to the stomach; while in birds, if present at all, they are
lower down, near the end of the gut. Some of the Vivipara also have processes connected with the lower part
of the gut which serve the same purpose as that stated above.

The whole tribe of fishes is of gluttonous appetite, owing to the arrangements for the reduction of their food
being very imperfect, and much of it consequently passing through them without undergoing concoction; and,
of all, those are the most gluttonous that have a straight intestine. For as the passage of food in such cases is
rapid, and the enjoyment derived from it in consequence but brief, it follows of necessity that the return of
appetite is also speedy.

It has already been mentioned that in animals with front teeth in both jaws the stomach is of small size. It
may be classed pretty nearly always under one or other of two headings, namely as resembling the stomach of
the dog, or as resembling the stomach of the pig. In the pig the stomach is larger than in the dog, and presents
certain folds of moderate size, the purpose of which is to lengthen out the period of concoction; while the
stomach of the dog is of small size, not much larger in calibre than the gut, and smooth on the internal
surface.

Not much larger, I say, than the gut; for in all animals after the stomach comes the gut. This, like the
stomach, presents numerous modifications. For in some animals it is uniform, when uncoiled, and alike
throughout, while in others it differs in different portions. Thus in some cases it is wider in the
neighbourhood of the stomach, and narrower towards the other end; and this explains by the way why dogs
have to strain so much in discharging their excrement. But in most animals it is the upper portion that is the
narrower and the lower that is of greater width.

Of greater length than in other animals, and much convoluted, are the intestines of those that have horns.
These intestines, moreover, as also the stomach, are of ampler volume, in accordance with the larger size of
the body. For animals with horns are, as a rule, animals of no small bulk, because of the thorough elaboration

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ON THE PARTS OF ANIMALS

which their food undergoes. The gut, except in those animals where it is straight, invariably widens out as we
get farther from the stomach and come to what is called the colon, and to a kind of caecal dilatation. After
this it again becomes narrower and convoluted. Then succeeds a straight portion which runs right on to the
vent. This vent is known as the anus, and is in some animals surrounded by fat, in others not so. All these
parts have been so contrived by nature as to harmonize with the various operations that relate to the food and
its residue. For, as the residual food gets farther on and lower down, the space to contain it enlarges, allowing
it to remain stationary and undergo conversion. Thus is it in those animals which, owing either to their large
size, or to the heat of the parts concerned, require more nutriment, and consume more fodder than the rest.

Neither is it without a purpose, that, just as a narrower gut succeeds to the upper stomach, so also does the
residual food, when its goodness is thoroughly exhausted, pass from the colon and the ample space of the
lower stomach into a narrower channel and into the spiral coil. For so nature can regulate her expenditure and
prevent the excremental residue from being discharged all at once.

In all such animals, however, as have to be comparatively moderate in their alimentation, the lower stomach
presents no wide and roomy spaces, though their gut is not straight, but has a number of convolutions. For
amplitude of space causes desire for ample food, and straightness of the intestine causes quick return of
appetite. And thus it is that all animals whose food receptacles are either simple or spacious are of gluttonous
habits, the latter eating enormously at a meal, the former making meals at short intervals.

Again, since the food in the upper stomach, having just been swallowed, must of necessity be quite fresh,
while that which has reached the lower stomach must have had its juices exhausted and resemble dung, it
follows of necessity that there must also be some intermediate part, in which the change may be effected, and
where the food will be neither perfectly fresh nor yet dung. And thus it is that, in all such animals as we are
now considering, there is found what is called the jejunum; which is a part of the small gut, of the gut, that is,
which comes next to the stomach. For this jejunum lies between the upper cavity which contains the yet
unconcocted food and the lower cavity which holds the residual matter, which by the time it has got here has
become worthless. There is a jejunum in all these animals, but it is only plainly discernible in those of large
size, and this only when they have abstained from food for a certain time. For then alone can one hit on the
exact period when the food lies half-way between the upper and lower cavities; a period which is very short,
for the time occupied in the transition of food is but brief. In females this jejunum may occupy any part
whatsoever of the upper intestine, but in males it comes just before the caecum and the lower stomach.

What is known as rennet is found in all animals that have a multiple stomach, and in the hare among animals
whose stomach is single. In the former the rennet neither occupies the large paunch, nor the honeycomb bag,
nor the terminal reed, but is found in the cavity which separates this terminal one from the two first, namely
in the so-called manyplies. It is the thick character of their milk which causes all these animals to have
rennet; whereas in animals with a single stomach the milk is thin, and consequently no rennet is formed. It is
this difference in thickness which makes the milk of horned animals coagulate, while that of animals without
horns does not. Rennet forms in the hare because it feeds on herbage that has juice like that of the fig; for
juice of this kind coagulates the milk in the stomach of the sucklings. Why it is in the manyplies that rennet is
formed in animals with multiple stomachs has been stated in the Problems.

Book IV

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ON THE PARTS OF ANIMALS

THE account which has now been given of the viscera, the stomach, and the other several parts holds equally
good not only for the oviparous quadrupeds, but also for such apodous animals as the Serpents. These two
classes of animals are indeed nearly akin, a serpent resembling a lizard which has been lengthened out and
deprived of its feet. Fishes, again, resemble these two groups in all their parts, excepting that, while these,
being land animals, have a lung, fishes have no lung, but gills in its place. None of these animals, excepting
the tortoise, as also no fish, has a urinary bladder. For owing to the bloodlessness of their lung, they drink but
sparingly; and such fluid as they have is diverted to the scaly plates, as in birds it is diverted to the feathers,
and thus they come to have the same white matter on the surface of their excrement as we see on that of birds.
For in animals that have a bladder, its excretion when voided throws down a deposit of earthy brine in the
containing vessel. For the sweet and fresh elements, being light, are expended on the flesh.

Among the Serpents, the same peculiarity attaches to vipers, as among fishes attaches to Selachia. For both
these and vipers are externally viviparous, but previously produce ova internally.

The stomach in all these animals is single, just as it is single in all other animals that have teeth in front of
both jaws; and their viscera are excessively small, as always happens when there is no bladder. In serpents
these viscera are, moreover, differently shaped from those of other animals. For, a serpent's body being long
and narrow, its contents are as it were moulded into a similar form, and thus come to be themselves
elongated.

All animals that have blood possess an omentum, a mesentery, intestines with their appendages, and,
moreover, a diaphragm and a heart; and all, excepting fishes, a lung and a windpipe. The relative positions,
moreover, of the windpipe and the oesophagus are precisely similar in them all; and the reason is the same as
has already been given.

Almost all sanguineous animals have a gall-bladder. In some this is attached to the liver, in others separated
from that organ and attached to the intestines, being apparently in the latter case no less than in the former an
appendage of the lower stomach. It is in fishes that this is most clearly seen. For all fishes have a
gall-bladder; and in most of them it is attached to the intestine, being in some, as in the Amia, united with
this, like a border, along its whole length. It is similarly placed in most serpents There are therefore no good
grounds for the view entertained by some writers, that the gall exists for the sake of some sensory action. For
they say that its use is to affect that part of the soul which is lodged in the neighbourhood of the liver, vexing
this part when it is congealed, and restoring it to cheerfulness when it again flows free. But this cannot be.
For in some animals there is absolutely no gall-bladder at all — in the horse, for instance, the mule, the ass,
the deer, and the roe; and in others, as the camel, there is no distinct bladder, but merely small vessels of a
biliary character. Again, there is no such organ in the seal, nor, of purely sea-animals, in the dolphin. Even
within the limits of the same genus, some animals appear to have and others to be without it. Such, for
instance, is the case with mice; such also with man. For in some individuals there is a distinct gall-bladder
attached to the liver, while in others there is no gall-bladder at all. This explains how the existence of this
part in the whole genus has been a matter of dispute. For each observer, according as he has found it present
or absent in the individual cases he has examined, has supposed it to be present or absent in the whole genus.
The same has occurred in the case of sheep and of goats. For these animals usually have a gall-bladder; but,
while in some localities it is so enormously big as to appear a monstrosity, as is the case in Naxos, in others it
is altogether wanting, as is the case in a certain district belonging to the inhabitants of Chalcis in Euboea.
Moreover, the gall-bladder in fishes is separated, as already mentioned, by a considerable interval from the
liver. No less mistaken seems to be the opinion of Anaxagoras and his followers, that the gall-bladder is the

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cause of acute diseases, inasmuch as it becomes over-full, and spirts out its excess on to the lung, the
blood-vessels, and the ribs. For, almost invariably, those who suffer from these forms of disease are persons
who have no gall-bladder at all, as would be quite evident were they to be dissected. Moreover, there is no
kind of correspondence between the amount of bile which is present in these diseases and the amount which
is exuded. The most probable opinion is that, as the bile when it is present in any other part of the body is a
mere residuum or a product of decay, so also when it is present in the region of the liver it is equally
excremental and has no further use; just as is the case with the dejections of the stomach and intestines. For
though even the residua are occasionally used by nature for some useful purpose, yet we must not in all cases
expect to find such a final cause; for granted the existence in the body of this or that constituent, with such
and such properties, many results must ensue merely as necessary consequences of these properties. All
animals, then, whose is healthy in composition and supplied with none but sweet blood, are either entirely
without a gall-bladder on this organ, or have merely small bile-containing vessels; or are some with and
some without such parts. Thus it is that the liver in animals that have no gall-bladder is, as a rule, of good
colour and sweet; and that, when there is a gall-bladder, that part of the liver is sweetest which lies
immediately underneath it. But, when animals are formed of blood less pure in composition, the bile serves
for the excretion of its impure residue. For the very meaning of excrement is that it is the opposite of
nutriment, and of bitter that it is the opposite of sweet; and healthy blood is sweet. So that it is evident that
the bile, which is bitter, cannot have any use, but must simply be a purifying excretion. It was therefore no
bad saying of old writers that the absence of a gall-bladder gave long life. In so saying they had in mind deer
and animals with solid hoofs. For such have no gall-bladder and live long. But besides these there are other
animals that have no gall-bladder, though those old writers had not noticed the fact, such as the camel and
the dolphin; and these also are, as it happens, long-lived. Seeing, indeed, that the liver is not only useful, but
a necessary and vital part in all animals that have blood, it is but reasonable that on its character should
depend the length or the shortness of life. Nor less reasonable is it that this organ and none other should have
such an excretion as the bile. For the heart, unable as it is to stand any violent affection, would be utterly
intolerant of the proximity of such a fluid; and, as to the rest of the viscera, none excepting the liver are
necessary parts of an animal. It is the liver therefore that alone has this provision. In conclusion, wherever we
see bile we must take it to be excremental. For to suppose that it has one character in this part, another in that,
would be as great an absurdity as to suppose mucus or the dejections of the stomach to vary in character
according to locality and not to be excremental wherever found.

So much then of the gall-bladder, and of the reasons why some animals have one, while others have not. We
have still to speak of the mesentery and the omentum; for these are associated with the parts already
described and contained in the same cavity. The omentum, then, is a membrane containing fat; the fat being
suet or lard, according as the fat of the animal generally is of the former or latter description. What kinds of
animals are so distinguished has been already set forth in an earlier part of this treatise. This membrane, alike
in animals that have a single and in those that have a multiple stomach, grows from the middle of that organ,
along a line which is marked on it like a seam. Thus attached, it covers the rest of the stomach and the greater
part of the bowels, and this alike in all sanguineous animals, whether they live on land or in water. Now the
development of this part into such a form as has been described is the result of necessity. For, whenever solid
and fluid are mixed together and heated, the surface invariably becomes membranous and skin-like. But the
region in which the omentum lies is full of nutriment of such a mixed character. Moreover, in consequence of
the close texture of the membrane, that portion of the sanguineous nutriment will alone filter into it which is
of a greasy character; for this portion is composed of the finest particles; and when it has so filtered in, it will
be concocted by the heat of the part, and will be converted into suet or lard, and will not acquire a flesh-like
or sanguineous constitution. The development, then, of the omentum is simply the result of necessity. But
when once formed, it is used by nature for an end, namely, to facilitate and to hasten the concoction of food.
For all that is hot aids concoction; and fat is hot, and the omentum is fat. This too explains why it hangs from

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the middle of the stomach; for the upper part of the stomach has no need of it, being assisted in concoction by
the adjacent liver. Thus much as concerns the omentum.

The so-called mesentery is also a membrane; and extends continuously from the long stretch of intestine to
the great vessel and the aorta. In it are numerous and close-packed vessels, which run from the intestines to
the great vessel and to the aorta. The formation of this membrane we shall find to be the result of necessity, as
is that of the other [similar] parts. What, however, is the final cause of its existence in sanguineous animals is
manifest on reflection. For it is necessary that animals shall get nutriment from without; and, again, that this
shall be converted into the ultimate nutriment, which is then distributed as sustenance to the various parts;
this ultimate nutriment being, in sanguineous animals, what we call blood, and having, in bloodless animals,
no definite name. This being so, there must be channels through which the nutriment shall pass, as it were
through roots, from the stomach into the blood-vessels. Now the roots of plants are in the ground; for thence
their nutriment is derived. But in animals the stomach and intestines represent the ground from which the
nutriment is to be taken. The mesentery, then, is an organ to contain the roots; and these roots are the vessels
that traverse it. This then is the final cause of its existence. But how it absorbs nutriment, and how that
portion of the food which enters into the vessels is distributed by them to the various parts of the body, are
questions which will be considered when we come to deal with the generation and nutrition of animals.

The constitution of sanguineous animals, so far as the parts as yet mentioned are concerned, and the reasons
for such constitution, have now been set forth. In natural sequence we should next go on to the organs of
generation, as yet undescribed, on which depend the distinctions of male and female. But, inasmuch as we
shall have to deal specially with generation hereafter, it will be more convenient to defer the consideration of
these parts to that occasion.

Very different from the animals we have as yet considered are the Cephalopoda and the Crustacea. For these
have absolutely no viscera whatsoever; as is indeed the case with all bloodless animals, in which are included
two other genera, namely the Testacea and the Insects. For in none of them does the material out of which
viscera are formed exist. None of them, that is, have blood. The cause of this lies in their essential
constitution. For the presence of blood in some animals, its absence from others, must be included in the
conception which determines their respective essences. Moreover, in the animals we are now considering,
none of those final causes will be found to exist which in sanguineous animals determine the presence of
viscera. For they have no blood vessels nor urinary bladder, nor do they breathe; the only part that it is
necessary for them to have being that which is analogous to a heart. For in all animals there must be some
central and commanding part of the body, to lodge the sensory portion of the soul and the source of life. The
organs of nutrition are also of necessity present in them all. They differ, however, in character because of
differences of the habitats in which they get their subsistence.

In the Cephalopoda there are two teeth, enclosing what is called the mouth; and inside this mouth is a
flesh-like substance which represents a tongue and serves for the discrimination of pleasant and unpleasant
food. The Crustacea have teeth corresponding to those of the Cephalopoda, namely their anterior teeth, and
also have the fleshy representative of a tongue. This latter part is found, moreover, in all Testacea, and serves,
as in sanguineous animals, for gustatory sensations. Similarly provided also are the Insects. For some of
these, such as the Bees and the Flies, have, as already described, their proboscis protruding from the mouth;
while those others that have no such instrument in front have a part which acts as a tongue inside the mouth.
Such, for instance, is the case in the Ants and the like. As for teeth, some insects have them, the Bees and the
Ants for instance, though in a somewhat modified form, while others that live on fluid nutriment are without

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ON THE PARTS OF ANIMALS

them. For in many insects the teeth are not meant to deal with the food, but to serve as weapons.

In some Testacea, as was said in the first treatise, the organ which is called the tongue is of considerable
strength; and in the Cochli (Sea-snails) there are also two teeth, just as in the Crustacea. The mouth in the
Cephalopoda is succeeded by a long gullet. This leads to a crop, like that of a bird, and directly continuous
with this is the stomach, from which a gut runs without windings to the vent. The Sepias and the Poulps
resemble each other completely, so far as regards the shape and consistency of these parts. But not so the
Teuthides (Calamaries). Here, as in the other groups there are the two stomach-like receptacles; but the first
of these cavities has less resemblance to a crop, and in neither is the form [or the consistency] the same as in
the other kinds, the whole body indeed being made of a softer kind of flesh.

The object of this arrangement of the parts in question is the same in the Cephalopoda as in Birds; for these
also are all unable to masticate their food; and therefore it is that a crop precedes their stomach.

For purposes of defence, and to enable them to escape from their foes, the Cephalopoda have what is called
their ink. This is contained in a membranous pouch, which is attached to the body and provided with a
terminal outlet just at the point where what is termed the funnel gives issue to the residua of the stomach.
This funnel is placed on the ventral surface of the animal. All Cephalopoda alike have this characteristic ink,
but chief of all the Sepia, where it is more abundant than in the rest. When the animal is disturbed and
frightened it uses this ink to make the surrounding water black and turbid, and so, as it were, puts a shield in
front of its body.

In the Calamaries and the Poulps the ink-bag is placed in the upper part of the body, in close proximity to the
mytis, whereas in the Sepia it is lower down, against the stomach. For the Sepia has a more plentiful supply
of ink than the rest, inasmuch as it makes more use of it. The reasons for this are, firstly, that it lives near the
shore, and, secondly, that it has no other means of protection; whereas the Poulp has its long twining feet to
use in its defence, and is, moreover, endowed with the power of changing colour. This changing of colour,
like the discharge of ink, occurs as the result of fright. As to the Calamary, it lives far out at sea, being the
only one of the Cephalopoda that does so; and this gives it protection. These then are the reasons why the ink
is more abundant in the Sepia than in the Calamary, and this greater abundance explains the lower position;
for it allows the ink to be ejected with ease even from a distance. The ink itself is of an earthy character, in
this resembling the white deposit on the surface of a bird's excrement and the explanation in both cases is the
same, namely, the absence of a urinary bladder. For, in default of this, it is the ink that serves for the
excretion of the earthiest matter. And this is more especially the case in the Sepia, because there is a greater
proportion of earth in its composition than in that of the other Cephalopoda. The earthy character of its bone
is a clear indication of this. For in the Poulp there is no bone at all, and in the Calamary it is thin and
cartilaginous. Why this bone should be present in some Cephalopoda, and wanting in others, and how its
character varies in those that have it, has now been set forth.

These animals, having no blood, are in consequence cold and of a timid character. Now, in some animals,
fear causes a disturbance of the bowels, and, in others, a flow of urine from the bladder. Similarly in these it
produces a discharge of ink, and, though the ejection of this ink in fright, like that of the urine, is the result of
necessity, and, though it is of excremental character, yet it is used by nature for a purpose, namely, the
protection and safety of the animal that excretes it.

The Crustacea also, both the Caraboid forms and the Crabs, are provided with teeth, namely their two anterior
teeth; and between these they also present the tongue-like piece of flesh, as has indeed been already
mentioned. Directly after their mouth comes a gullet, which, if we compare relative sizes, is but small in
proportion to the body: and then a stomach, which in the Carabi and some of the Crabs is furnished with a
second set of teeth, the anterior teeth being insufficient for adequate mastication. From the stomach a uniform
gut runs in a direct line to the excremental vent.

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The parts described are to be found also in all the various Testacea. The degree of distinctness, however, with
which they are formed varies in the different kinds, and the larger the size of the animal the more easily
distinguishable are all these parts severally. In the Sea-snails, for example, we find teeth, hard and sharp, as
before mentioned, and between them the flesh-like substance, just as in the Crustacea and Cephalopoda, and
again the proboscis, which, as has been stated, is something between a sting and a tongue. Directly after the
mouth comes a kind of bird-like crop, then a gullet, succeeded by a stomach, in which is the mecon, as it is
styled; and continuous with this mecon is an intestine, starting directly from it. It is this residual substance
which appears in all the Testacea to form the most palatable morsel. Purpuras and Whelks, and all other
Testacea that have turbinate shells, in structure resemble the Sea-snail. The genera and species of Testacea
are very numerous. For there are those with turbinate shells, of which some have just been mentioned; and,
besides these, there are bivalves and univalves. Those with turbinate shells may, indeed, after a certain
fashion be said to resemble bivalves. For they all from their very birth have an operculum to protect that part
of their body which is exposed to view. This is the case with the Purpuras, with Whelks, with the Nerites, and
the like. Were it not for this, the part which is undefended by the shell would be very liable to injury by
collision with external objects. The univalves also are not without protection. For on their dorsal surface they
have a shell, and by the under surface they attach themselves to the rocks, and so after a manner become
bivalved, the rock representing the second valve. Of these the animals known as Limpets are an example. The
bivalves, scallops and mussels, for instance, are protected by the power they have of closing their valves; and
the Turbinata by the operculum just mentioned, which transforms them, as it were, crom univalves into
bivalves. But of all there is none so perfectly protected as the sea-urchin. For here there is a globular shell
which encloses the body completely, and which is, moreover, set with sharp spines. This peculiarity
distinguishes the sea-urchin from all other Testacea, as has already been mentioned.

The structure of the Testacea and of the Crustacea is exactly the reverse of that of the Cephalopoda. For in the
latter the fleshy substance is on the outside and the earthy substance within, whereas in the former the soft
parts are inside and the hard part without. In the sea-urchin, however, there is no fleshy part whatsoever.

All the Testacea then, those that have not been mentioned as well as those that have, agree as stated in
possessing a mouth with the tongue-like body, a stomach, and a vent for excrement, but they differ from
each other in the positions and proportions of these parts. The details, however, of these differences must be
looked for in the Researches concerning Animals and the treatises on Anatomy. For while there are some
points which can be made clear by verbal description, there are others which are more suited for ocular
demonstration.

Peculiar among the Testacea are the sea-urchins and the animals known as Tethya (Ascidians). The
sea-urchins have five teeth, and in the centre of these the fleshy body which is common to all the animals we
have been discussing. Immediately after this comes a gullet, and then the stomach, divided into a number of
separate compartments, which look like so many distinct stomachs; for the cavities are separate and all
contain abundant residual matter. They are all, however, connected with one and the same oesophagus, and
they all end in one and the same excremental vent. There is nothing besides the stomach of a fleshy character,
as has already been stated. All that can be seen are the so-called ova, of which there are several, contained
each in a separate membrane, and certain black bodies which have no name, and which, beginning at the
animal's mouth, are scattered round its body here and there promiscuously. These sea-urchins are not all of
one species, but there are several different kinds, and in all of them the parts mentioned are to be found. It is
not, however, in every kind that the so-called ova are edible. Neither do these attain to any size in any other
species than that with which we are all familiar. A similar distinction may be made generally in the case of all
Testacea. For there is a great difference in the edible qualities of the flesh of different kinds; and in some,
moreover, the residual substance known as the mecon is good for food, while in others it is uneatable. This
mecon in the turbinated genera is lodged in the spiral part of the shell, while in univalves, such as limpets, it
occupies the fundus, and in bivalves is placed near the hinge, the so-called ovum lying on the right; while on
the opposite side is the vent. The former is incorrectly termed ovum, for it merely corresponds to what in

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ON THE PARTS OF ANIMALS

well-fed sanguineous animals is fat; and thus it is that it makes its appearance in Testacea at those seasons of
the year when they are in good condition, namely, spring and autumn. For no Testacea can abide extremes of
temperature, and they are therefore in evil plight in seasons of great cold or heat. This is clearly shown by
what occurs in the case of the sea-urchins. For though the ova are to be found in these animals even directly
they are born, yet they acquire a greater size than usual at the time of full moon; not, as some think, because
sea-urchins eat more at that season, but because the nights are then warmer, owing to the moonlight. For
these creatures are bloodless, and so are unable to stand cold and require warmth. Therefore it is that they are
found in better condition in summer than at any other season; and this all over the world excepting in the
Pyrrhean tidal strait. There the sea-urchins flourish as well in winter as in summer. But the reason for this is
that they have a greater abundance of food in the winter, because the fish desert the strait at that season.

The number of the ova is the same in all sea-urchins, and is an odd one. For there are five ova, just as there
are also five teeth and five stomachs; and the explanation of this is to be found in the fact that the so-called
ova are not really ova, but merely, as was said before, the result of the animal's well-fed condition. Oysters
also have a so-called ovum, corresponding in character to that of the sea-urchins, but existing only on one
side of their body. Now inasmuch as the sea-urchin is of a spherical form, and not merely a single disk like
the oyster, and in virtue of its spherical shape is the same from whatever side it be examined, its ovum must
necessarily be of a corresponding symmetry. For the spherical shape has not the asymmetry of the
disk-shaped body of the oysters. For in all these animals the head is central, but in the sea-urchin the
so-called ovum is above [and symmetrical, while in the oyster it is only one side]. Now the necessary
symmetry would be observed were the ovum to form a continuous ring. But this may not be. For it would be
in opposition to what prevails in the whole tribe of Testacea; for in all the ovum is discontinuous, and in all
excepting the sea-urchins asymmetrical, being placed only on one side of the body. Owing then to this
necessary discontinuity of the ovum, which belongs to the sea-urchin as a member of the class, and owing to
the spherical shape of its body, which is its individual peculiarity, this animal cannot possibly have an even
number of ova. For were they an even number, they would have to be arranged exactly opposite to each
other, in pairs, so as to keep the necessary symmetry; one ovum of each pair being placed at one end, the
other ovum at the other end of a transverse diameter. This again would violate the universal provision in
Testacea. For both in the oysters and in the scallops we find the ovum only on one side of the circumference.
The number then of the ova must be uneven, three for instance, or five. But if there were only three they
would be much too far apart; while, if there were more than five, they would come to form a continuous
mass. The former arrangement would be disadvantageous to the animal, the latter an impossibility. There can
therefore be neither more nor less than five. For the same reason the stomach is divided into five parts, and
there is a corresponding number of teeth. For seeing that the ova represent each of them a kind of body for
the animal, their disposition must conform to that of the stomach, seeing that it is from this that they derive
the material for their growth. Now if there were only one stomach, either the ova would be too far off from it,
or it would be so big as to fill up the whole cavity, and the sea-urchin would have great difficulty in moving
about and finding due nourishment for its repletion. As then there are five intervals between the five ova, so
are there of necessity five divisions of the stomach, one for each interval. So also, and on like grounds, there
are five teeth. For nature is thus enabled to allot to each stomachal compartment and ovum its separate and
similar tooth. These, then, are the reasons why the number of ova in the sea-urchin is an odd one, and why
that odd number is five. In some sea-urchins the ova are excessively small, in others of considerable size, the
explanation being that the latter are of a warmer constitution, and so are able to concoct their food more
thoroughly; while in the former concoction is less perfect, so that the stomach is found full of residual matter,
while the ova are small and uneatable. Those of a warmer constitution are, moreover, in virtue of their
warmth more given to motion, so that they make expeditions in search of food, instead of remaining
stationary like the rest. As evidence of this, it will be found that they always have something or other sticking
to their spines, as though they moved much about; for they use their spines as feet.

The Ascidians differ but slightly from plants, and yet have more of an animal nature than the sponges, which
are virtually plants and nothing more. For nature passes from lifeless objects to animals in such unbroken

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ON THE PARTS OF ANIMALS

sequence, interposing between them beings which live and yet are not animals, that scarcely any difference
seems to exist between two neighbouring groups owing to their close proximity.

A sponge, then, as already said, in these respects completely resembles a plant, that throughout its life it is
attached to a rock, and that when separated from this it dies. Slightly different from the sponges are the
so-called Holothurias and the sea-lungs, as also sundry other sea-animals that resemble them. For these are
free and unattached. Yet they have no feeling, and their life is simply that of a plant separated from the
ground. For even among land-plants there are some that are independent of the soil, and that spring up and
grow, either upon other plants, or even entirely free. Such, for example, is the plant which is found on
Parnassus, and which some call the Epipetrum. This you may hang up on a peg and it will yet live for a
considerable time. Sometimes it is a matter of doubt whether a given organism should be classed with plants
or with animals. The Ascidians, for instance, and the like so far resemble plants as that they never live free
and unattached, but, on the other hand, inasmuch as they have a certain flesh-like substance, they must be
supposed to possess some degree of sensibility.

An Ascidian has a body divided by a single septum and with two orifices, one where it takes in the fluid
matter that ministers to its nutrition, the other where it discharges the surplus of unused juice, for it has no
visible residual substance, such as have the other Testacea. This is itself a very strong justification for
considering an Ascidian, and anything else there may be among animals that resembles it, to be of a
vegetable character; for plants also never have any residuum. Across the middle of the body of these
Ascidians there runs a thin transverse partition, and here it is that we may reasonably suppose the part on
which life depends to be situated.

The Acalephae, or Sea-nettles, as they are variously called, are not Testacea at all, but lie outside the
recognized groups. Their constitution, like that of the Ascidians, approximates them on one side to plants, on
the other to animals. For seeing that some of them can detach themselves and can fasten upon their food, and
that they are sensible of objects which come in contact with them, they must be considered to have an animal
nature. The like conclusion follows from their using the asperity of their bodies as a protection against their
enemies. But, on the other hand, they are closely allied to plants, firstly by the imperfection of their structure,
secondly by their being able to attach themselves to the rocks, which they do with great rapidity, and lastly by
their having no visible residuum notwithstanding that they possess a mouth.

Very similar again to the Acalephae are the Starfishes. For these also fasten on their prey, and suck out its
juices, and thus destroy a vast number of oysters. At the same time they present a certain resemblance to such
of the animals we have described as the Cephalopoda and Crustacea, inasmuch as they are free and
unattached. The same may also be said of the Testacea.

Such, then, is the structure of the parts that minister to nutrition and which every animal must possess. But
besides these organs it is quite plain that in every animal there must be some part or other which shall be
analogous to what in sanguineous animals is the presiding seat of sensation. Whether an animal has or has not
blood, it cannot possibly be without this. In the Cephalopoda this part consists of a fluid substance contained
in a membrane, through which runs the gullet on its way to the stomach. It is attached to the body rather
towards its dorsal surface, and by some is called the mytis. Just such another organ is found also in the
Crustacea and there too is known by the same name. This part is at once fluid and corporeal and, as before
said, is traversed by the gullet. For had the gullet been placed between the mytis and the dorsal surface of the
animal, the hardness of the back would have interfered with its due dilatation in the act of deglutition. On the
outer surface of the mytis runs the intestine; and in contact with this latter is placed the ink-bag, so that it
may be removed as far as possible from the mouth and its obnoxious fluid be kept at a distance from the
nobler and sovereign part. The position of the mytis shows that it corresponds to the heart of sanguineous
animals; for it occupies the self-same place. The same is shown by the sweetness of its fluid, which has the
character of concocted matter and resembles blood.

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ON THE PARTS OF ANIMALS

In the Testacea the presiding seat of sensation is in a corresponding position, but is less easily made out. It
should, however, always be looked for in some midway position; namely, in such Testacea as are stationary,
midway between the part by which food is taken in and the channel through which either the excrement or the
spermatic fluid is voided, and, in those species which are capable of locomotion, invariably midway between
the right and left sides.

In Insects this organ, which is the seat of sensation, lies, as was stated in the first treatise, between the head
and the cavity which contains the stomach. In most of them it consists of a single part; but in others, for
instance in such as have long bodies and resemble the Juli (Millipedes), it is made up of several parts, so that
such insects continue to live after they have been cut in pieces. For the aim of nature is to give to each animal
only one such dominant part; and when she is unable to carry out this intention she causes the parts, though
potentially many, to work together actually as one. This is much more clearly marked in some insects than in
others.

The parts concerned in nutrition are not alike in all insects, but show considerable diversity. Thus some have
what is called a sting in the mouth, which is a kind of compound instrument that combines in itself the
character of a tongue and of lips. In others that have no such instrument in front there is a part inside the
mouth that answers the same sensory purposes. Immediately after the mouth comes the intestine, which is
never wanting in any insect. This runs in a straight line and without further complication to the vent;
occasionally, however, it has a spiral coil. There are, moreover, some insects in which a stomach succeeds to
the mouth, and is itself succeeded by a convoluted intestine, so that the larger and more voracious insects
may be enabled to take in a more abundant supply of food. More curious than any are the Cicadae. For here
the mouth and the tongue are united so as to form a single part, through which, as through a root, the insect
sucks up the fluids on which it lives. Insects are always small eaters, not so much because of their diminutive
size as because of their cold temperament. For it is heat which requires sustenance; just as it is heat which
speedily concocts it. But cold requires no sustenance. In no insects is this so conspicuous as in these Cicadae.
For they find enough to live on in the moisture which is deposited from the air. So also do the Ephemera that
are found about the Black sea. But while these latter only live for a single day, the Cicadae subsist on such
food for several days, though still not many.

We have now done with the internal parts of animals, and must therefore return to the consideration of the
external parts which have not yet been described. It will be better to change our order of exposition and begin
with the animals we have just been describing, so that proceeding from these, which require less discussion,
our account may have more time to spend on the perfect kinds of animals, those namely that have blood.

We will begin with Insects. These animals, though they present no great multiplicity of parts, are not without
diversities when compared with each other. They are all manyfooted; the object of this being to compensate
their natural slowness and frigidity, and give greater activity to their motions. Accordingly we find that those
which, as the (Millipedes), have long bodies, and are therefore the most liable to refrigeration, have also the
greatest number of feet. Again, the body in these animals is insected-the reason for this being that they have
not got one vital centre but many-and the number of their feet corresponds to that of the insections.

Should the feet fall short of this, their deficiency is compensated by the power of flight. Of such flying insects
some live a wandering life, and are forced to make long expeditions in search of food. These have a body of
light weight, and four feathers, two on either side, to support it. Such are bees and the insects akin to them.
When, however, such insects are of very small bulk, their feathers are reduced to two, as is the case with flies.
Insects with heavy bodies and of stationary habits, though not polypterous in the same way as bees, yet have
sheaths to their feathers to maintain their efficiency. Such are the Melolonthae and the like. For their

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ON THE PARTS OF ANIMALS

stationary habits expose their feathers to much greater risks than are run by those of insects that are more
constantly in flight, and on this account they are provided with this protecting shield. The feather of an insect
has neither barbs nor shaft. For, though it is called a feather, it is no feather at all, but merely a skin-like
membrane that, owing to its dryness, necessarily becomes detached from the surface of the body, as the
fleshy substance grows cold.

These animals then have their bodies insected, not only for the reasons already assigned, but also to enable
them to curl round in such a manner as may protect them from injury; for such insects as have long bodies
can roll themselves up, which would be impossible were it not for the insections; and those that cannot do
this can yet draw their segments up into the insected spaces, and so increase the hardness of their bodies. This
can be felt quite plainly by putting the finger on one of the insects, for instance, known as Canthari. The
touch frightens the insect, and it remains motionless, while its body becomes hard. The division of the body
into segments is also a necessary result of there being several supreme organs in place of one; and this again
is a part of the essential constitution of insects, and is a character which approximates them to plants. For as
plants, though cut into pieces, can still live, so also can insects. There is, however, this difference between the
two cases, that the portions of the divided insect live only for a limited time, whereas the portions of the plant
live on and attain the perfect form of the whole, so that from one single plant you may obtain two or more.

Some insects are also provided with another means of protection against their enemies, namely a sting. In
some this is in front, connected with the tongue, in others behind at the posterior end. For just as the organ of
smell in elephants answers several uses, serving alike as a weapon and for purposes of nutrition, so does also
the sting, when placed in connexion with the tongue, as in some insects, answer more than one end. For it is
the instrument through which they derive their sensations of food, as well as that with which they suck it up
and bring it to the mouth. Such of these insects as have no anterior sting are provided with teeth, which serve
in some of them for biting the food, and in others for its prehension and conveyance to the mouth. Such are
their uses, for instance, in ants and all the various kinds of bees. As for the insects that have a sting behind,
this weapon is given them because they are of a fierce disposition. In some of them the sting is lodged inside
the body, in bees, for example, and wasps. For these insects are made for flight, and were their sting external
and of delicate make it would soon get spoiled; and if, on the other hand, it were of thicker build, as in
scorpions, its weight would be an incumbrance. As for scorpions that live on the ground and have a tail, their
sting must be set upon this, as otherwise it would be of no use as a weapon. Dipterous insects never have a
posterior sting. For the very reason of their being dipterous is that they are small and weak, and therefore
require no more than two feathers to support their light weight; and the same reason which reduces their
feathers to two causes their sting to be in front; for their strength is not sufficient to allow them to strike
efficiently with the hinder part of the body. Polypterous insects, on the other hand, are of greater bulk-indeed
it is this which causes them to have so many feathers; and their greater size makes them stronger in their
hinder parts. The sting of such insects is therefore placed behind. Now it is better, when possible, that one and
the same instrument shall not be made to serve several dissimilar uses; but that there shall be one organ to
serve as a weapon, which can then be very sharp, and a distinct one to serve as a tongue, which can then be of
spongy texture and fit to absorb nutriment. Whenever, therefore, nature is able to provide two separate
instruments for two separate uses, without the one hampering the other, she does so, instead of acting like a
coppersmith who for cheapness makes a spit and lampholder in one. It is only when this is impossible that
she uses one organ for several functions.

The anterior legs are in some cases longer than the others, that they may serve to wipe away any foreign
matter that may lodge on the insect's eyes and obstruct its sight, which already is not very distinct owing to
the eyes being made of a hard substance. Flies and bees and the like may be constantly seen thus dressing
themselves with crossed forelegs. Of the other legs, the hinder are bigger than the middle pair, both to aid in
running and also that the insect, when it takes flight, may spring more easily from the ground. This difference
is still more marked in such insects as leap, in locusts for instance, and in the various kinds of fleas. For these
first bend and then extend the legs, and, by doing so, are necessarily shot up from the ground. It is only the.

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ON THE PARTS OF ANIMALS

hind legs of locusts, and not the front ones, that resemble the steering oars of a ship. For this requires that the
joint shall be deflected inwards, and such is never the case with the anterior limbs. The whole number of legs,
including those used in leaping, is six in all these insects.

In the Testacea the body consists of but few parts, the reason being that these animals live a stationary life.
For such animals as move much about must of necessity have more numerous parts than such as remain
quiet; for their activities are many, and the more diversified the movements the greater the number of organs
required to effect them. Some species of Testacea are absolutely motionless, and others not quite but nearly
so. Nature, however, has provided them with a protection in the hardness of the shell with which she has
invested their body. This shell, as already has been said, may have one valve, or two valves, or be turbinate.
In the latter case it may be either spiral, as in whelks, or merely globular, as in sea-urchins. When it has two
valves, these may be gaping, as in scallops and mussels, where the valves are united together on one side
only, so as to open and shut on the other; or they may be united together on both sides, as in the Solens
(razor-fishes). In all cases alike the Testacea have, like plants, the head downwards. The reason for this is,
that they take in their nourishment from below, just as do plants with their roots. Thus the under parts come
in them to be above, and the upper parts to be below. The body is enclosed in a membrane, and through this
the animal filters fluid free from salt and absorbs its nutriment. In all there is a head; but none of the parts,
excepting this recipient of food, has any distinctive name.

All the Crustacea can crawl as well as swim, and accordingly they are provided with numerous feet. There
are four main genera, viz. the Carabi, as they are called, the Astaci, the Carides, and the Carcini. In each of
these genera, again, there are numerous species, which differ from each other not only as regards shape, but
also very considerably as regards size. For, while in some species the individuals are large, in others they are
excessively minute. The Carcinoid and Caraboid Crustacea resemble each other in possessing claws. These
claws are not for locomotion, but to serve in place of hands for seizing and holding objects; and they are
therefore bent in the opposite direction to the feet, being so twisted as to turn their convexity towards the
body, while their feet turn towards it their concavity. For in this position the claws are best suited for laying
hold of the food and carrying it to the mouth. The distinction between the Carabi and the Carcini (Crabs)
consists in the former having a tail while the latter have none. For the Carabi swim about and a tail is
therefore of use to them, serving for their propulsion like the blade of an oar. But it would be of no use to the
Crabs; for these animals live habitually close to the shore, and creep into holes and corners. In such of them
as live out at sea, the feet are much less adapted for locomotion than in the rest, because they are little given
to moving about but depend for protection on their shell-like covering. The Maiae and the crabs known as
Heracleotic are examples of this; the legs in the former being very thin, in the latter very short.

The very minute crabs that are found among the small fry at the bottom of the net have their hindermost feet
flattened out into the semblance of fins or oar-blades, so as to help the animal in swimming.

The Carides are distinguished from the Carcinoid species by the presence of a tail; and from the Caraboids by
the absence of claws. This is explained by their large number of feet, on which has been expended the
material for the growth of claws. Their feet again are numerous to suit their mode of progression, which is
mainly by swimming.

Of the parts on the ventral surface, those near the head are in some of these animals formed like gills, for the
admission and discharge of water; while the parts lower down differ in the two sexes. For in the female
Carabi these are more laminar than in the males, and in the female crabs the flap is furnished with hairier

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ON THE PARTS OF ANIMALS

appendages. This gives ampler space for the disposal of the ova, which the females retain in these parts
instead of letting them go free, as do fishes and all other oviparous animals. In the Carabi and in the Crabs the
right claw is invariably the larger and the stronger. For it is natural to every animal in active operations to use
the parts on its right side in preference to those on its left; and nature, in distributing the organs, invariably
assigns each, either exclusively or in a more perfect condition, to such animals as can use it. So it is with
tusks, and teeth, and horns, and spurs, and all such defensive and offensive weapons.

In the Lobsters alone it is a matter of chance which claw is the larger, and this in either sex. Claws they must
have, because they belong to a genus in which this is a constant character; but they have them in this
indeterminate way, owing to imperfect formation and to their not using them for their natural purpose, but for
locomotion.

For a detailed account of the several parts of these animals, of their position and their differences, those parts
being also included which distinguish the sexes, reference must be made to the treatises on Anatomy and to
the Researches concerning Animals.

We come now to the Cephalopoda. Their internal organs have already been described with those of other
animals. Externally there is the trunk of the body, not distinctly defined, and in front of this the head
surrounded by feet, which form a circle about the mouth and teeth, and are set between these and the eyes.
Now in all other animals the feet, if there are any, are disposed in one of two ways; either before and behind
or along the sides, the latter being the plan in such of them, for instance, as are bloodless and have numerous
feet. But in the Cephalopoda there is a peculiar arrangement, different from either of these. For their feet are
all placed at what may be called the fore end. The reason for this is that the hind part of their body has been
drawn up close to the fore part, as is also the case in the turbinated Testacea. For the Testacea, while in some
points they resemble the Crustacea, in others resemble the Cephalopoda. Their earthy matter is on the outside,
and their fleshy substance within. So far they are like the Crustacea. But the general plan of their body is that
of the Cephalopoda; and, though this is true in a certain degree of all the Testacea, it is more especially true
of those turbinated species that have a spiral shell. Of this general plan, common to the two, we will speak
presently. But let us first consider the case of quadrupeds and of man, where the arrangement is that of a
straight line. Let A at the upper end of such a line be supposed to represent the mouth, then B the gullet, and
C the stomach, and the intestine to run from this C to the excremental vent where D is inscribed. Such is the
plan in sanguineous animals; and round this straight line as an axis are disposed the head and so-called trunk;
the remaining parts, such as the anterior and posterior limbs, having been superadded by nature, merely to
minister to these and for locomotion.

In the Crustacea also and in Insects there is a tendency to a similar arrangement of the internal parts in a
straight line; the distinction between these groups and the sanguineous animals depending on differences of
the external organs which minister to locomotion. But the Cephalopoda and the turbinated Testacea have in
common an arrangement which stands in contrast with this. For here the two extremities are brought together
by a curve, as if one were to bend the straight line marked E until D came close to Such, then, is the
disposition of the internal parts; and round these, in the Cephalopoda, is placed the sac (in the Poulps alone
called a head), and, in the Testacea, the turbinate shell which corresponds to the sac. There is, in fact, only
this difference between them, that the investing substance of the Cephalopoda is soft while the shell of the
Testacea is hard, nature having surrounded their fleshy part with this hard coating as a protection because of
their limited power of locomotion. In both classes, owing to this arrangement of the internal organs, the
excrement is voided near the mouth; at a point below this orifice in the Cephalopoda, and in the Turbinata on
one side of it.

ON THE PARTS OF ANIMALS

Such, then, is the explanation of the position of the feet in the Cephalopoda, and of the contrast they present
to other animals in this matter. The arrangement, however, in the Sepias and the Calamaries is not precisely
the same as in the Poulps, owing to the former having no other mode of progression than by swimming, while
the latter not only swim but crawl. For in the former six of the feet are above the teeth and small, the outer
one on either side being the biggest; while the remaining two, which make up the total weight, are below the
mouth and are the biggest of all, just as the hind limbs in quadrupeds are stronger than the fore limbs. For it is
these that have to support the weight, and to take the main part in locomotion. And the outer two of the upper
six are bigger than the pair which intervene between them and the uppermost of all, because they have to
assist the lowermost pair in their office. In the Poulps, on the other hand, the four central feet are the biggest.
Again, though the number of feet is the same in all the Cephalopoda, namely eight, their length varies in
different kinds, being short in the Sepias and the Calamaries, but greater in the Poulps. For in these latter the
trunk of the body is of small bulk, while in the former it is of considerable size; and so in the one case nature
has used the materials subtracted from the body to give length to the feet, while in the other she has acted in
precisely the opposite way, and has given to the growth of the body what she has first taken from the feet.
The Poulps, then, owing to the length of their feet, can not only swim but crawl, whereas in the other genera
the feet are useless for the latter mode of progression, being small while the bulk of the body is considerable.
These short feet would not enable their possessors to cling to the rocks and keep themselves from being torn
off by the waves when these run high in times of storm; neither would they serve to lay hold of objects at all
remote and bring them in; but, to supply these defects, the animal is furnished with two long proboscises, by
which it can moor itself and ride at anchor like a ship in rough weather. These same processes serve also to
catch prey at a distance and to bring it to the mouth. They are so used by both the Sepias and the Calamaries.
In the Poulps the feet are themselves able to perform these offices, and there are consequently no proboscises.
Proboscises and twining tentacles, with acetabula set upon them, act in the same way and have the same
structure as those plaited instruments which were used by physicians of old to reduce dislocations of the
fingers. Like these they are made by the interlacing of their fibres, and they act by pulling upon pieces of
flesh and yielding substances. For the plaited fibres encircle an object in a slackened condition, and when
they are put on the stretch they grasp and cling tightly to whatever it may be that is in contact with their inner
surface. Since, then, the Cephalopoda have no other instruments with which to convey anything to
themselves from without, than either twining tentacles, as in some species, or proboscises as in others, they
are provided with these to serve as hands for offence and defence and other necessary uses.

The acetabula are set in double line in all the Cephalopoda excepting in one kind of poulp, where there is but
a single row. The length and the slimness which is part of the nature of this kind of poulp explain the
exception. For a narrow space cannot possibly admit of more than a single row. This exceptional character,
then, belongs to them, not because it is the most advantageous arrangement, but because it is the necessary
consequence of their essential specific constitution.

In all these animals there is a fin, encircling the sac. In the Poulps and the Sepias this fin is unbroken and
continuous, as is also the case in the larger calamaries known as Teuthi. But in the smaller kind, called
Teuthides, the fin is not only broader than in the Sepias and the Poulps, where it is very narrow, but,
moreover, does not encircle the entire sac, but only begins in the middle of the side. The use of this fin is to
enable the animal to swim, and also to direct its course. It acts, that is, like the rump-feathers in birds, or the
tail-fin in fishes. In none is it so small or so indistinct as in the Poulps. For in these the body is of small bulk
and can be steered by the feet sufficiently well without other assistance.

The Insects, the Crustacea, the Testacea, and the Cephalopoda, have now been dealt with in turn; and their
parts have been described, whether internal or external.

ON THE PARTS OF ANIMALS

We must now go back to the animals that have blood, and consider such of their parts, already enumerated, as
were before passed over. We will take the viviparous animals first, and, we have done with these, will pass on
to the oviparous, and treat of them in like manner.

The parts that border on the head, and on what is known as the neck and throat, have already been taken into
consideration. All animals that have blood have a head; whereas in some bloodless animals, such as crabs, the
part which represents a head is not clearly defined. As to the neck, it is present in all the Vivipara, but only in
some of the Ovipara; for while those that have a lung also have a neck, those that do not inhale the outer air
have none. The head exists mainly for the sake of the brain. For every animal that has blood must of necessity
have a brain; and must, moreover, for reasons already given, have it placed in an opposite region to the heart.
But the head has also been chosen by nature as the part in which to set some of the senses; because its blood
is mixed in such suitable proportions as to ensure their tranquillity and precision, while at the same time it
can supply the brain with such warmth as it requires. There is yet a third constituent superadded to the head,
namely the part which ministers to the ingestion of food. This has been placed here by nature, because such a
situation accords best with the general configuration of the body. For the stomach could not possibly be
placed above the heart, seeing that this is the sovereign organ; and if placed below, as in fact it is, then the
mouth could not possibly be placed there also. For this would have necessitated a great increase in the length
of the body; and the stomach, moreover, would have been removed too far from the source of motion and of
concoction.

The head, then, exists for the sake of these three parts; while the neck, again, exists for the sake of the
windpipe. For it acts as a defence to this and to the oesophagus, encircling them and keeping them from
injury. In all other animals this neck is flexible and contains several vertebrae; but in wolves and lions it
contains only a single bone. For the object of nature was to give these animals an organ which should be
serviceable in the way of strength, rather than one that should be useful for any of the other purposes to which
necks are subservient.

Continuous with the head and neck is the trunk with the anterior limbs. In man the forelegs and forefeet are
replaced by arms and by what we call hands. For of all animals man alone stands erect, in accordance with
his godlike nature and essence. For it is the function of the god-like to think and to be wise; and no easy task
were this under the burden of a heavy body, pressing down from above and obstructing by its weight the
motions of the intellect and of the general sense. When, moreover, the weight and corporeal substance
become excessive, the body must of necessity incline towards the ground. In such cases therefore nature, in
order to give support to the body, has replaced the arms and hands by forefeet, and has thus converted the
animal into a quadruped. For, as every animal that walks must of necessity have the two hinder feet, such an
animal becomes a quadruped, its body inclining downwards in front from the weight which its soul cannot
sustain. For all animals, man alone excepted, are dwarf-like in form. For the dwarf-like is that in which the
upper part is large, while that which bears the weight and is used in progression is small. This upper part is
what we call the trunk, which reaches from the mouth to the vent. In man it is duly proportionate to the part
below, and diminishes much in its comparative size as the man attains to full growth. But in his infancy the
contrary obtains, and the upper parts are large, while the lower part is small; so that the infant can only crawl,
and is unable to walk; nay, at first cannot even crawl, but remains without motion. For all children are dwarfs
in shape, but cease to be so as they become men, from the growth of their lower part; whereas in quadrupeds
the reverse occurs, their lower parts being largest in youth, and advance of years bringing increased growth
above, that is in the trunk, which extends from the rump to the head. Thus it is that colts are scarcely, if at all,
below full-grown horses in height; and that while still young they can touch their heads with the hind legs,
though this is no longer possible when they are older. Such, then, is the form of animals that have either a
solid or a cloven hoof. But such as are polydactylous and without horns, though they too are of dwarf-like

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shape, are so in a less degree; and therefore the greater growth of the lower parts as compared with the upper
is also small, being proportionate to this smaller deficiency.

Dwarf-like again is the race of birds and fishes; and so in fact, as already has been said, is every animal that
has blood. This is the reason why no other animal is so intelligent as man. For even among men themselves if
we compare children with adults, or such adults as are of dwarf-like shape with such as are not, we find that,
whatever other superiority the former may possess, they are at any rate deficient as compared with the latter
in intelligence. The explanation, as already stated, is that their psychical principle is corporeal, and much
impeded in its motions. Let now a further decrease occur in the elevating heat, and a further increase in the
earthy matter, and the animals become smaller in bulk, and their feet more numerous, until at a later stage
they become apodous, and extended full length on the ground. Then, by further small successions of change,
they come to have their principal organ below; and at last their cephalic part becomes motionless and
destitute of sensation. Thus the animal becomes a plant, that has its upper parts downwards and its lower
parts above. For in plants the roots are the equivalents of mouth and head, while the seed has an opposite
significance, for it is produced above it the extremities of the twigs.

The reasons have now been stated why some animals have many feet, some only two, and others none; why,
also, some living things are plants and others animals; and, lastly, why man alone of all animals stands erect.
Standing thus erect, man has no need of legs in front, and in their stead has been endowed by nature with
arms and hands. Now it is the opinion of Anaxagoras that the possession of these hands is the cause of man
being of all animals the most intelligent. But it is more rational to suppose that his endowment with hands is
the consequence rather than the cause of his superior intelligence. For the hands are instruments or organs,
and the invariable plan of nature in distributing the organs is to give each to such animal as can make use of
it; nature acting in this matter as any prudent man would do. For it is a better plan to take a person who is
already a flute-player and give him a flute, than to take one who possesses a flute and teach him the art of
flute-playing. For nature adds that which is less to that which is greater and more important, and not that
which is more valuable and greater to that which is less. Seeing then that such is the better course, and seeing
also that of what is possible nature invariably brings about the best, we must conclude that man does not owe
his superior intelligence to his hands, but his hands to his superior intelligence. For the most intelligent of
animals is the one who would put the most organs to use; and the hand is not to be looked on as one organ but
as many; for it is, as it were, an instrument for further instruments. This instrument, therefore,-the hand-of
all instruments the most variously serviceable, has been given by nature to man, the animal of all animals the
most capable of acquiring the most varied handicrafts.

Much in error, then, are they who say that the construction of man is not only faulty, but inferior to that of all
other animals; seeing that he is, as they point out, bare-footed, naked, and without weapon of which to avail
himself. For other animals have each but one mode of defence, and this they can never change; so that they
must perform all the offices of life and even, so to speak, sleep with sandals on, never laying aside whatever
serves as a protection to their bodies, nor changing such single weapon as they may chance to possess. But to
man numerous modes of defence are open, and these, moreover, he may change at will; as also he may adopt
such weapon as he pleases, and at such times as suit him. For the hand is talon, hoof, and horn, at will. So too
it is spear, and sword, and whatsoever other weapon or instrument you please; for all these can it be from its
power of grasping and holding them all. In harmony with this varied office is the form which nature has
contrived for it. For it is split into several divisions, and these are capable of divergence. Such capacity of
divergence does not prevent their again converging so as to form a single compact body, whereas had the
hand been an undivided mass, divergence would have been impossible. The divisions also may be used singly
or two together and in various combinations. The joints, moreover, of the fingers are well constructed for
prehension and for pressure. One of these also, and this not long like the rest but short and thick, is placed
laterally. For were it not so placed all prehension would be as impossible, as were there no hand at all. For the
pressure of this digit is applied from below upwards, while the rest act from above downwards; an
arrangement which is essential, if the grasp is to be firm and hold like a tight clamp. As for the shortness of

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this digit, the object is to increase its strength, so that it may be able, though but one, to counterbalance its
more numerous opponents. Moreover, were it long it would be of no use. This is the explanation of its being
sometimes called the great digit, in spite of its small size; for without it all the rest would be practically
useless. The finger which stands at the other end of the row is small, while the central one of all is long, like a
centre oar in a ship. This is rightly so; for it is mainly by the central part of the encircling grasp that a tool
must be held when put to use.

No less skilfully contrived are the nails. For, while in man these serve simply as coverings to protect the tips
of the fingers, in other animals they are also used for active purposes; and their form in each case is suited to
their office.

The arms in man and the fore limbs in quadrupeds bend in contrary directions, this difference having
reference to the ingestion of food and to the other offices which belong to these parts. For quadrupeds must of
necessity bend their anterior limbs inwards that they may serve in locomotion, for they use them as feet. Not
but what even among quadrupeds there is at any rate a tendency for such as are polydactylous to use their
forefeet not only for locomotion but as hands. And they are in fact so used, as any one may see. For these
animals seize hold of objects, and also repel assailants with their anterior limbs; whereas quadrupeds with
solid hoofs use their hind legs for this latter purpose. For their fore limbs are not analogous to the arms and
hands of man.

It is this hand-like office of the anterior limbs which explains why in some of the polydactylous quadrupeds,
such as wolves, lions, dogs, and leopards, there are actually five digits on each forefoot, though there are only
four on each hind one. For the fifth digit of the foot corresponds to the fifth digit of the hand, and like it is
called the big one. It is true that in the smaller polydactylous quadrupeds the hind feet also have each five
toes. But this is because these animals are creepers; and the increased number of nails serves to give them a
tighter grip, and so enables them to creep up steep places with greater facility, or even to run head
downwards.

In man between the arms, and in other animals between the forelegs, lies what is called the breast. This in
man is broad, as one might expect; for as the arms are set laterally on the body, they offer no impediment to
such expansion in this part. But in quadrupeds the breast is narrow, owing to the legs having to be extended
in a forward direction in progression and locomotion.

Owing to this narrowness the mammae of quadrupeds are never placed on the breast. But in the human body
there is ample space in this part; moreover, the heart and neighbouring organs require protection, and for
these reasons this part is fleshy and the mammae are placed upon it separately, side by side, being themselves
of a fleshy substance in the male and therefore of use in the way just stated; while in the female, nature, in
accordance with what we say is her frequent practice, makes them minister to an additional function,
employing them as a store-place of nutriment for the offspring. The human mammae are two in number, in
accordance with the division of the body into two halves, a right and a left. They are somewhat firmer than
they would otherwise be, because the ribs in this region are joined together; while they form two separate
masses, because their presence is in no wise burdensome. In other animals than man, it is impossible for the
mammae to be placed on the breast between the forelegs, for they would interfere with locomotion; they are
therefore disposed of otherwise, and in a variety of ways. Thus in such animals as produce but few at a birth,
whether horned quadrupeds or those with solid hoofs, the mammae are placed in the region of the thighs, and
are two in number, while in such as produce litters, or such as are polydactylous, the dugs are either
numerous and placed laterally on the belly, as in swine and dogs, or are only two in number, being set,
however, in the centre of the abdomen, as is the case in the lion. The explanation of this latter condition is not
that the lion produces few at a birth, for sometimes it has more than two cubs at a time, but is to be found in
the fact that this animal has no plentiful supply of milk. For, being a flesheater, it gets food at but rare
intervals, and such nourishment as it obtains is all expended on the growth of its body.

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In the elephant also there are but two mammae, which are placed under the axillae of the fore limbs. The
mammae are not more than two, because this animal has only a single young one at a birth; and they are not
placed in the region of the thighs, because they never occupy that position in any polydactylous animal such
as this. Lastly, they are placed above, close to the axillae, because this is the position of the foremost dugs in
all animals whose dugs are numerous, and the dugs so placed give the most milk. Evidence of this is
furnished by the sow. For she always presents these foremost dugs to the first-born of her litter. A single
young one is of course a first-born, and so such animals as only produce a single young one must have these
anterior dugs to present to it; that is they must have the dugs which are under the axillae. This, then, is the
reason why the elephant has but two mammae, and why they are so placed. But, in such animals as have
litters of young, the dugs are disposed about the belly; the reason being that more dugs are required by those
that will have more young to nourish. Now it is impossible that these dugs should be set transversely in rows
of more than two, one, that is, for each side of the body, the right and the left; they must therefore be placed
lengthways, and the only place where there is sufficient length for this is the region between the front and
hind legs. As to the animals that are not polydactylous but produce few at a birth, or have horns, their dugs
are placed in the region of the thighs. The horse, the ass, the camel are examples; all of which bear but a
single young one at a time, and of which the two former have solid hoofs, while in the last the hoof is cloven.
As still further examples may be mentioned the deer, the ox, the goat, and all other similar animals.

The explanation is that in these animals growth takes place in an upward direction; so that there must be an
abundant collection of residual matter and of blood in the lower region, that is to say in the neighbourhood of
the orifices for efflux, and here therefore nature has placed the mammae. For the place in which the nutriment
is set in motion must also be the place whence nutriment can be derived by them. In man there are mammae
in the male as well as in the female; but some of the males of other animals are without them. Such, for
instance, is the case with horses, some stallions being destitute of these parts, while others that resemble their
dams have them. Thus much then concerning the mammae.

Next after the breast comes the region of the belly, which is left unenclosed by the ribs for a reason which has
already been given; namely that there may be no impediment to the swelling which necessarily occurs in the
food as it gets heated, nor to the expansion of the womb in pregnancy.

At the extreme end of what is called the trunk are the parts concerned in the evacuation of the solid and also
of the fluid residue. In all sanguineous animals with some few exceptions, and in all Vivipara without any
exception at all, the same part which serves for the evacuation of the fluid residue is also made by nature to
serve in sexual congress, and this alike in male and female. For the semen is a kind of fluid and residual
matter. The proof of this will be given hereafter, but for the present let it taken for granted. (The like holds
good of the menstrual fluid in women, and of the part where they emit semen. This also, however, is a matter
of which a more accurate account will be given hereafter. For the present let it be simply stated as a fact, that
the catamenia of the female like the semen of the male are residual matter. Both of them, moreover, being
fluid, it is only natural that the parts which serve for voidance of the urine should give issue to residues which
resemble it in character.) Of the internal structure of these parts, and of the differences which exist between
the parts concerned with semen and the parts concerned with conception, a clear account is given in the book
of Researches concerning Animals and in the treatises on Anatomy. Moreover, I shall have to speak of them
again when I come to deal with Generation. As regards, however, the external shape of these parts, it is plain
enough that they are adapted to their operations, as indeed of necessity they must be. There are, however,
differences in the male organ corresponding to differences in the body generally. For all animals are not of an
equally sinewy nature. This organ, again, is the only one that, independently of any morbid change, admits of
augmentation and of diminution of bulk. The former condition is of service in copulation, while the other is
required for the advantage of the body at large. For, were the organ constantly in the former condition, it
would be an incumbrance. The organ therefore has been formed of such constituents as will admit of either
state. For it is partly sinewy, partly cartilaginous, and thus is enabled either to contract or to become
extended, and is capable of admitting air.

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All female quadrupeds void their urine backwards, because the position of the parts which this implies is
useful to them in the act of copulation. This is the case with only some few males, such as the lynx, the lion,
the camel, and the hare. No quadruped with a solid hoof is retromingent.

The posterior portion of the body and the parts about the legs are peculiar in man as compared with
quadrupeds. Nearly all these latter have a tail, and this whether they are viviparous or oviparous. For, even if
the tail be of no great size, yet they have a kind of scut, as at any rate a small representative of it. But man is
tail-less. He has, however, buttocks, which exist in none of the quadrupeds. His legs also are fleshy (as too
are his thighs and feet); while the legs in all other animals that have any, whether viviparous or not, are
fleshless, being made of sinew and bone and spinous substance. For all these differences there is, so to say,
one common explanation, and this is that of all animals man alone stands erect. It was to facilitate the
maintenance of this position that Nature made his upper parts light, taking away some of their corporeal
substance, and using it to increase the weight of lithe parts below, so that the buttocks, the thighs, and the
calves of the legs were all made fleshy. The character which she thus gave to the buttocks renders them at the
same time useful in resting the body. For standing causes no fatigue to quadrupeds, and even the long
continuance of this posture produces in them no weariness; for they are supported the whole time by four
props, which is much as though they were lying down. But to man it is no task to remain for any length of
time on his feet, his body demanding rest in a sitting position. This, then, is the reason why man has buttocks
and fleshy legs; and the presence of these fleshy parts explains why he has no tail. For the nutriment which
would otherwise go to the tail is used up in the production of these parts, while at the same time the existence
of buttocks does away with the necessity of a tail. But in quadrupeds and other animals the reverse obtains.
For they are of dwarf-like form, so that all the pressure of their weight and corporeal substance is on their
upper part, and is withdrawn from the parts below. On this account they are without buttocks and have hard
legs. In order, however, to cover and protect that part which serves for the evacuation of excrement, nature
has given them a tail of some kind or other, subtracting for the purpose some of the nutriment which would
otherwise go to the legs. Intermediate in shape between man and quadrupeds is the ape, belonging therefore
to neither or to both, and having on this account neither tail nor buttocks; no tail in its character of biped, no
buttocks in its character of quadruped. There is great diversity of so-called tails; and this organ like others is
sometimes used by nature for by-purposes, being made to serve not only as a covering and protection to the
fundament, but also for other uses and advantages of its possessor.

There are differences in the feet of quadrupeds. For in some of these animals there is a solid hoof, and in
others a hoof cloven into two, and again in others a foot divided into many parts.

The hoof is solid when the body is large and the earthy matter present in great abundance; in which case the
earth, instead of forming teeth and horns, is separated in the character of a nail, and being very abundant
forms one continuous nail, that is a hoof, in place of several. This consumption of the earthy matter on the
hoof explains why these animals, as a rule, have no huckle-bones; a second reason being that the presence of
such a bone in the joint of the hind leg somewhat impedes its free motion. For extension and flexion can be
made more rapidly in parts that have but one angle than in parts that have several. But the presence of a
huckle-bone, as a connecting bolt, is the introduction as it were of a new limb-segment between the two
ordinary ones. Such an addition adds to the weight of the foot, but renders the act of progression more secure.
Thus it is that in such animals as have a hucklebone, it is only in the posterior and not in the anterior limbs
that this bone is found. For the anterior limbs, moving as they do in advance of the others, require to be light
and capable of ready flexion, whereas firmness and extensibility are what are wanted in the hind limbs.
Moreover, a huckle-bone adds weight to the blow of a limb, and so renders it a suitable weapon of defence;
and these animals all use their hind legs to protect themselves, kicking out with their heels against anything
which annoys them. In the cloven-hoofed quadrupeds the lighter character of the hind legs admits of there
being a huckle-bone; and the presence of the huckle-bone prevents them from having a solid hoof, the bony
substance remaining in the joint, and therefore being deficient in the foot. As to the polydactylous
quadrupeds, none of them have huckle-bones. For if they had they would not be polydactylous, but the

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divisions of the foot would only extend to that amount of its breadth which was covered by the huckle-bone.
Thus it is that most of the animals that have huckle-bones are cloven-hoofed.

Of all animals man has the largest foot in proportion to the size of the body. This is only what might be
expected. For seeing that he is the only animal that stands erect, the two feet which are intended to bear all
the weight of the body must be both long and broad. Equally intelligible is it that the proportion between the
size of the fingers and that of the whole hand should be inverted in the case of the toes and feet. For the
function of the hands is to take hold of objects and retain them by pressure; so that the fingers require to be
long. For it is by its flexed portion that the hand grasps an object. But the function of the feet is to enable us
to stand securely, and for this the undivided part of the foot requires to be of larger size than the toes.
However, it is better for the extremity to be divided than to be undivided. For in an undivided foot disease of
any one part would extend to the whole organ; whereas, if the foot be divided into separate digits, there is not
an equal liability to such an occurrence. The digits, again, by being short would be less liable to injury. For
these reasons the feet in man are many-toed, while the separate digits are of no great length. The toes,
finally, are furnished with nails for the same reason as are the fingers, namely because such projecting parts
are weak and therefore require special protection.

We have now done with such sanguineous animals as live on land and bring forth their young alive; and,
having dealt with all their main kinds, we may pass on to such sanguineous animals as are oviparous. Of
these some have four feet, while others have none. The latter form a single genus, namely the Serpents; and
why these are apodous has been already explained in the dissertation on Animal Progression. Irrespective of
this absence of feet, serpents resemble the oviparous quadrupeds in their conformation.

In all these animals there is a head with its component parts; its presence being determined by the same
causes as obtain in the case of other sanguineous animals; and in all, with the single exception of the river
crocodile, there is a tongue inside the mouth. In this one exception there would seem to be no actual tongue,
but merely a space left vacant for it. The reason is that a crocodile is in a way a land-animal and a
water-animal combined. In its character of land-animal it has a space for a tongue; but in its character of
water-animal it is without the tongue itself. For in some fishes, as has already been mentioned, there is no
appearance whatsoever of a tongue, unless the mouth be stretched open very widely indeed; while in others it
is indistinctly separated from the rest of the mouth. The reason for this is that a tongue would be of but little
service to such animals, seeing that they are unable to chew their food or to taste it before swallowing, the
pleasurable sensations they derive from it being limited to the act of deglutition. For it is in their passage
down the gullet that solid edibles cause enjoyment, while it is by the tongue that the savour of fluids is
perceived. Thus it is during deglutition that the oiliness, the heat, and other such qualities of food are
recognized; and, in fact, the satisfaction from most solid edibles and dainties is derived almost entirely from
the dilatation of the oesophagus during deglutition. This sensation, then, belongs even to animals that have no
tongue, but while other animals have in addition the sensations of taste, tongueless animals have, we may
say, no other satisfaction than it. What has now been said explains why intemperance as regards drinks and
savoury fluids does not go hand in hand with intemperance as regards eating and solid relishes.

In some oviparous quadrupeds, namely in lizards, the tongue is bifid, as also it is in serpents, and its terminal
divisions are of hair-like fineness, as has already been described. (Seals also have a forked tongue.) This it is
which accounts for all these animals being so fond of dainty food. The teeth in the four-footed Ovipara are of
the sharp interfitting kind, like the teeth of fishes. The organs of all the senses are present and resemble those
of other animals. Thus there are nostrils for smell, eves for vision, and ears for hearing. The latter organs,
however, do not project from the sides of the head, but consist simply of the duct, as also is the case in birds.
This is due in both cases to the hardness of the integument; birds having their bodies covered with feathers,

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and these oviparous quadrupeds with horny plates. These plates are equivalent to scales, but of a harder
character. This is manifest in tortoises and river crocodiles, and also in the large serpents. For here the plates
become stronger than the bones, being seemingly of the same substance as these.

These animals have no upper eyelid, but close the eye with the lower lid In this they resemble birds, and the
reason is the same as was assigned in their case. Among birds there are some that can not only thus close the
eye, but can also blink by means of a membrane which comes from its corner. But none of the oviparous
quadrupeds blink; for their eyes are harder than those of birds. The reason for this is that keen vision and
far-sightedness are of very considerable service to birds, flying as they do in the air, whereas they would be
of comparatively small use to the oviparous quadrupeds, seeing that they are all of troglodytic habits.

Of the two separate portions which constitute the head, namely the upper part and the lower jaw, the latter in
man and in the viviparous quadrupeds moves not only upwards and downwards, but also from side to side;
while in fishes, and birds and oviparous quadrupeds, the only movement is up and down. The reason is that
this latter movement is the one required in biting and dividing food, while the lateral movement serve to
reduce substances to a pulp. To such animals, therefore, as have grinder-teeth this lateral motion is of
service; but to those animals that have no grinders it would be quite useless, and they are therefore invariably
without it. For nature never makes anything that is superfluous. While in all other animals it is the lower jaw
that is movable, in the river crocodile it is exceptionally the upper. This is because the feet in this creature are
so excessively small as to be useless for seizing and holding prey; on which account nature has given it a
mouth that can serve for these purposes in their stead. For that direction of motion which will give the greater
force to a blow will be the more serviceable one in holding or in seizing prey; and a blow from above is
always more forcible than one from below. Seeing, then, that both the prehension and the mastication of food
are offices of the mouth, and that the former of these two is the more essential in an animal that has neither
hands nor suitably formed feet, these crocodiles will derive greater benefit from a motion of the upper jaw
downwards than from a motion of the lower jaw upwards. The same considerations explain why crabs also
move the upper division of each claw and not the lower. For their claws are substitutes for hands, and so
require to be suitable for the prehension of food, and not for its comminution; for such comminution and
biting is the office of teeth. In crabs, then, and in such other animals as are able to seize their food in a
leisurely manner, inasmuch as their mouth is not called on to perform its office while they are still in the
water, the two functions are assigned to different parts, prehension to the hands or feet, biting and
comminution of food to the mouth. But in crocodiles the mouth has been so framed by nature as to serve both
purposes, the jaws being made to move in the manner just described.

Another part present in these animals is a neck, this being the necessary consequence of their having a lung.
For the windpipe by which the air is admitted to the lung is of some length. If, however, the definition of a
neck be correct, which calls it the portion between the head and the shoulders, a serpent can scarcely be said
with the same right as the rest of these animals to have a neck, but only to have something analogous to that
part of the body. It is a peculiarity of serpents, as compared with other animals allied to them, that they are
able to turn their head backwards without stirring the rest of the body. The reason of this is that a serpent, like
an insect, has a body that admits of being curled up, its vertebrae being cartilaginous and easily bent. The
faculty in question belongs then to serpents simply as a necessary consequence of this character of their
vertebrae; but at the same time it has a final cause, for it enables them to guard against attacks from behind.
For their body, owing to its length and the absence of feet, is ill-suited for turning round and protecting the
hinder parts; and merely to lift the head, without the power of turning it round, would be of no use
whatsoever.

The animals with which we are dealing have, moreover, a part which corresponds to the breast; but neither
here nor elsewhere in their body have they any mammae, as neither has any bird or fish. This is a
consequence of their having no milk; for a mamma is a receptacle for milk and, as it were, a vessel to contain
it. This absence of milk is not peculiar to these animals, but is common to all such as are not internally

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viviparous. For all such produce eggs, and the nutriment which in Vivipara has the character of milk is in
them engendered in the egg. Of all this, however, a clearer account will be given in the treatise on
Generation. As to the mode in which the legs bend, a general account, in which all animals are considered,
has already been given in the dissertation on Progression. These animals also have a tail, larger in some of
them, smaller in others, and the reason for this has been stated in general terms in an earlier passage.

Of all oviparous animals that live on land there is none so lean as the Chamaeleon. For there is none that has
so little blood. The explanation of this is to be found in the psychical temperament of the creature. For it is of
a timid nature, as the frequent changes it undergoes in its outward aspect testify. But fear is a refrigeration,
and results from deficiency of natural heat and scantiness of blood. We have now done with such
sanguineous animals as are quadrupedous and also such as are apodous, and have stated with sufficient
completeness what external parts they possess, and for what reason they have them.

The differences of birds compared one with another are differences of magnitude, and of the greater or
smaller development of parts. Thus some have long legs, others short legs; some have a broad tongue, others
a narrow tongue; and so on with the other parts. There are few of their parts that differ save in size, taking
birds by themselves. But when birds are compared with other animals the parts present differences of form
also. For in some animals these are hairy, in others scaly, and in others have scale-like plates, while birds are
feathered.

Birds, then, are feathered, and this is a character common to them all and peculiar to them. Their feathers,
too, are split and distinct in kind from the undivided feathers of insects; for the bird's feather is barbed, these
are not; the bird's feather has a shaft, these have none. A second strange peculiarity which distinguishes birds
from all other animals is their beak. For as in elephants the nostril serves in place of hands, and as in some
insects the tongue serves in place of mouth, so in birds there is a beak, which, being bony, serves in place of
teeth and lips. Their organs of sense have already been considered.

All birds have a neck extending from the body; and the purpose of this neck is the same as in such other
animals as have one. This neck in some birds is long, in others short; its length, as a general rule, being pretty
nearly determined by that of the legs. For long-legged birds have a long neck, short-legged birds a short one,
to which rule, however, the web-footed birds form an exception. For to a bird perched up on long legs a short
neck would be of no use whatsoever in collecting food from the ground; and equally useless would be a long
neck, if the legs were short. Such birds, again, as are carnivorous would find length in this part interfere
greatly with their habits of life. For a long neck is weak, and it is on their superior strength that carnivorous
birds depend for their subsistence. No bird, therefore, that has talons ever has an elongated neck. In
web-footed birds, however, and in those other birds belonging to the same class, whose toes though actually
separate have flat marginal lobes, the neck is elongated, so as to be suitable for collecting food from the
water; while the legs are short, so as to serve in swimming. The beaks of birds, as their feet, vary with their
modes of life. For in some the beak is straight, in others crooked; straight, in those who use it merely for
eating; crooked, in those that live on raw flesh. For a crooked beak is an advantage in fighting; and these
birds must, of course, get their food from the bodies of other animals, and in most cases by violence. In such
birds, again, as live in marshes and are herbivorous the beak is broad and flat, this form being best suited for
digging and cropping, and for pulling up plants. In some of these marsh birds, however, the beak is elongated,
as too is the neck, the reason for this being that the bird get its food from some depth below the surface. For
most birds of this kind, and most of those whose feet are webbed, either in their entirety or each part
separately, live by preying on some of the smaller animals that are to be found in water, and use these parts
for their capture, the neck acting as a fishing-rod, and the beak representing the line and hook.

12 69

ON THE PARTS OF ANIMALS

The upper and under sides of the body, that is of what in quadrupeds is called the trunk, present in birds one
unbroken surface, and they have no arms or forelegs attached to it, but in their stead wings, which are a
distinctive peculiarity of these animals; and, as these wings are substitutes for arms, their terminal segments
lie on the back in the place of a shoulder-blade.

The legs are two in number, as in man; not however, as in man, bent outwards, but bent inwards like the legs
of a quadruped. The wings are bent like the forelegs of a quadruped, having their convexity turned outwards.
That the feet should be two in number is a matter of necessity. For a bird is essentially a sanguineous animal,
and at the same time essentially a winged animal; and no sanguineous animal has more than four points for
motion In birds, then, as in those other sanguineous animals that live and move upon the ground, the limbs
attached to the trunk are four in number. But, while in all the rest these four limbs consist of a pair of arms
and a pair of legs, or of four legs as in quadrupeds, in birds the arms or forelegs are replaced by a pair of
wings, and this is their distinctive character. For it is of the essence of a bird that it shall be able to fly; and it
is by the extension of wings that this is made possible. Of all arrangements, then, the only possible, and so the
necessary, one is that birds shall have two feet; for this with the wings will give them four points for motion.
The breast in all birds is sharp-edged, and fleshy. The sharp edge is to minister to flight, for broad surfaces
move with considerable difficulty, owing to the large quantity of air which they have to displace; while the
fleshy character acts as a protection, for the breast, owing to its form, would be weak, were it not amply
covered.

Below the breast lies the belly, extending, as in quadrupeds and in man, to the vent and to the place where the
legs are jointed to the trunk.

Such, then, are the parts which lie between the wings and the legs. Birds like all other animals, whether
produced viviparously or from eggs, have an umbilicus during their development, but, when the bird has
attained to fuller growth, no signs of this remain visible. The cause of this is plainly to be seen during the
process of development; for in birds the umbilical cord unites with the intestine, and is not a portion of the
vascular system, as is the case in viviparous animals.

Some birds, again, are well adapted for flight, their wings being large and strong. Such, for instance, are those
that have talons and live on flesh. For their mode of life renders the power of flight a necessity, and it is on
this account that their feathers are so abundant and their wings so large. Besides these, however, there are
also other genera of birds that can fly well; all those, namely, that depend on speed for security, or that are of
migratory habits. On the other hand, some kinds of birds have heavy bodies and are not constructed for flight.
These are birds that are frugivorous and live on the ground, or that are able to swim and get their living in
watery places. In those that have talons the body, without the wings, is small; for the nutriment is consumed
in the production of these wings, and of the weapons and defensive appliances; whereas in birds that are not
made for flight the contrary obtains, and the body is bulky and so of heavy weight. In some of these
heavy-bodied birds the legs are furnished with what are called spurs, which replace the wings as a means of
defence. Spurs and talons never co-exist in the same bird. For nature never makes anything superfluous; and
if a bird can fly, and has talons, it has no use for spurs; for these are weapons for fighting on the ground, and
on this account are an appanage of certain heavy-bodied birds. These latter, again, would find the possession
of talons not only useless but actually injurious; for the claws would stick into the ground and interfere with
progression. This is the reason why all birds with talons walk so badly, and why they never settle upon rocks.
For the character of their claws is ill-suited for either action.

All this is the necessary consequence of the process of development. For the earthy matter in the body issuing
from it is converted into parts that are useful as weapons. That which flows upwards gives hardness or size to
the beak; and, should any flow downwards, it either forms spurs upon the legs or gives size and strength to
the claws upon the feet. But it does not at one and the same time produce both these results, one in the legs,
the other in the claws; for such a dispersion of this residual matter would destroy all its efficiency. In other

12 70

ON THE PARTS OF ANIMALS

birds this earthy residue furnishes the legs with the material for their elongation; or sometimes, in place of
this, fills up the interspaces between the toes. Thus it is simply a matter of necessity, that such birds as swim
shall either be actually web-footed, or shall have a kind of broad blade-like margin running along the whole
length of each distinct toe. The forms, then, of these feet are simply the necessary results of the causes that
have been mentioned. Yet at the same time they are intended for the animal's advantage. For they are in
harmony with the mode of life of these birds, who, living on the water, where their wings are useless, require
that their feet shall be such as to serve in swimming. For these feet are so developed as to resemble the oars
of a boat, or the fins of a fish; and the destruction of the foot-web has the same effect as the destruction of
the fins; that is to say, it puts an end to all power of swimming.

In some birds the legs are very long, the cause of this being that they inhabit marshes. I say the cause,
because nature makes the organs for the function, and not the function for the organs. It is, then, because
these birds are not meant for swimming that their feet are without webs, and it is because they live on ground
that gives way under the foot that their legs and toes are elongated, and that these latter in most of them have
an extra number of joints. Again, though all birds have the same material composition, they are not all made
for flight; and in these, therefore, the nutriment that should go to their tail-feathers is spent on the legs and
used to increase their size. This is the reason why these birds when they fly make use of their legs as a tail,
stretching them out behind, and so rendering them serviceable, whereas in any other position they would be
simply an impediment.

In other birds, where the legs are short, these are held close against the belly during flight. In some cases this
is merely to keep the feet out of the way, but in birds that have talons the position has a further purpose, being
the one best suited for rapine. Birds that have a long and a thick neck keep it stretched out during flight; but
those whose neck though long is slender fly with it coiled up. For in this position it is protected, and less
likely to get broken, should the bird fly against any obstacle.

In all birds there is an ischium, but so placed and of such length that it would scarcely be taken for an
ischium, but rather for a second thigh-bone; for it extends as far as to the middle of the belly. The reason for
this is that the bird is a biped, and yet is unable to stand erect. For if its ischium extended but a short way
from the fundament, and then immediately came the leg, as is the case in man and in quadrupeds, the bird
would be unable to stand up at all. For while man stands erect, and while quadrupeds have their heavy bodies
propped up in front by the forelegs, birds can neither stand erect owing to their dwarf-like shape, nor have
anterior legs to prop them up, these legs being replaced by wings. As a remedy for this Nature has given them
a long ischium, and brought it to the centre of the body, fixing it firmly; and she has placed the legs under this
central point, that the weight on either side may be equally balanced, and standing or progression rendered
possible. Such then is the reason why a bird, though it is a biped, does not stand erect. Why its legs are
destitute of flesh has also already been stated; for the reasons are the same as in the case of quadrupeds.

In all birds alike, whether web-footed or not, the number of toes in each foot is four. For the Libyan ostrich
may be disregarded for the present, and its cloven hoof and other discrepancies of structure as compared with
the tribe of birds will be considered further on. Of these four toes three are in front, while the fourth points
backward, serving, as a heel, to give steadiness. In the long-legged birds this fourth toe is much shorter than
the others, as is the case with the Crex, but the number of their toes is not increased. The arrangement of the
toes is such as has been described in all birds with the exception of the wryneck. Here only two of the toes are
in front, the other two behind; and the reason for this is that the body of the wryneck is not inclined forward
so much as that of other birds. All birds have testicles; but they are inside the body. The reason for this will
be given in the treatise On the Generation of Animals.

12 71

ON THE PARTS OF ANIMALS

Thus then are fashioned the parts of birds. But in fishes a still further stunting has occurred in the external
parts. For here, for reasons already given, there are neither legs nor hands nor wings, the whole body from
head to tail presenting one unbroken surface. This tail differs in different fishes, in some approximating in
character to the fins, while in others, namely in some of the flat kinds, it is spinous and elongated, because the
material which should have gone to the tail has been diverted thence and used to increase the breadth of the
body. Such, for instance, is the case with the Torpedos, the Trygons, and whatever other Selachia there may
be of like nature. In such fishes, then, the tail is spinous and long; while in some others it is short and fleshy,
for the same reason which makes it spinous and long in the Torpedo. For to be short and fleshy comes to the
same thing as to be long and less amply furnished with flesh.

What has occurred in the Fishing-frog is the reverse of what has occurred in the other instances just given.
For here the anterior and broad part of the body is not of a fleshy character, and so all the fleshy substance
which has been thence diverted has been placed by nature in the tail and hinder portion of the body.

In fishes there are no limbs attached to the body. For in accordance with their essential constitution they are
swimming animals; and nature never makes anything superfluous or void of use. Now inasmuch as fishes are
made swimming they have fins, and as they are not made for walking they are without feet; for feet are
attached to the body that they may be of use in progression on land. Moreover, fishes cannot have feet, or any
other similar limbs, as well as four fins; for they are essentially sanguineous animals. The Cordylus, though it
has gills, has feet, for it has no fins but merely has its tail flattened out and loose in texture.

Fishes, unless, like the Batos and the Trygon, they are broad and flat, have four fins, two on the upper and
two on the under side of the body; and no fish ever has more than these. For, if it had, it would be a bloodless
animal.

The upper pair of fins is present in nearly all fishes, but not so the under pair; for these are wanting in some
of those fishes that have long thick bodies, such as the eel, the conger, and a certain kind of Cestreus that is
found in the lake at Siphae. When the body is still more elongated, and resembles that of a serpent rather than
that of a fish, as is the case in the Smuraena, there are absolutely no fins at all; and locomotion is effected by
the flexures of the body, the water being put to the same use by these fishes as is the ground by serpents. For
serpents swim in water exactly in the same way as they glide on the ground. The reason for these serpent-like
fishes being without fins is the same as that which causes serpents to be without feet; and what this is has
been already stated in the dissertations on the Progression and the Motion of Animals. The reason was this. If
the points of motion were four, motion would be effected under difficulties; for either the two pairs of fins
would be close to each other, in which case motion would scarcely be possible, or they would be at a very
considerable distance apart, in which case the long interval between them would be just as great an evil. On
the other hand, to have more than four such motor points would convert the fishes into bloodless animals. A
similar explanation applies to the case of those fishes that have only two fins. For here again the body is of
great length and like that of a serpent, and its undulations do the office of the two missing fins. It is owing to
this that such fishes can even crawl on dry ground, and can live there for a considerable time; and do not
begin to gasp until they have been for a considerable time out of the water, while others, whose nature is akin
to that of land-animals, do not even do as much as that. In such fishes as have but two fins it is the upper pair
(pectorals) that is present, excepting when the flat broad shape of the body prevents this. The fins in such
cases are placed at the head, because in this region there is no elongation, which might serve in the absence of
fins as a means of locomotion; whereas in the direction of the tail there is a considerable lengthening out in
fishes of this conformation. As for the Bati and the like, they use the marginal part of their flattened bodies in
place of fins for swimming.

13 72

ON THE PARTS OF ANIMALS

In the Torpedo and the Fishing-frog the breadth of the anterior part of the body is not so great as to render
locomotion by fins impossible, but in consequence of it the upper pair (pectorals) are placed further back and
the under pair (ventrals) are placed close to the head, while to compensate for this advancement they are
reduced in size so as to be smaller than the upper ones. In the Torpedo the two upper fins (pectorals) are
placed on the tail, and the fish uses the broad expansion of its body to supply their place, each lateral half of
its circumference serving the office of a fin.

The head, with its several parts, as also the organs of sense, have already come under consideration.

There is one peculiarity which distinguishes fishes from all other sanguineous animals, namely, the
possession of gills. Why they have these organs has been set forth in the treatise on Respiration. These gills
are in most fishes covered by opercula, but in the Selachia, owing to the skeleton being cartilaginous, there
are no such coverings. For an operculum requires fish-spine for its formation, and in other fishes the skeleton
is made of this substance, whereas in the Selachia it is invariably formed of cartilage. Again, while the
motions of spinous fishes are rapid, those of the Selachia are sluggish, inasmuch as they have neither
fish-spine nor sinew; but an operculum requires rapidity of motion, seeing that the office of the gills is to
minister as it were to expiration. For this reason in Selachia the branchial orifices themselves effect their own
closure, and thus there is no need for an operculum to ensure its taking place with due rapidity. In some fishes
the gills are numerous, in others few in number; in some again they are double, in others single. The last gill
in most cases is single. For a detailed account of all this, reference must be made to the treatises on Anatomy,
and to the book of Researches concerning Animals.

It is the abundance or the deficiency of the cardiac heat which determines the numerical abundance or
deficiency of the gills. For, the greater an animal's heat, the more rapid and the more forcible does it require
the branchial movement to be; and numerous and double gills act with more force and rapidity than such as
are few and single. Thus, too, it is that some fishes that have but few gills, and those of comparatively small
efficacy, can live out of water for a considerable time; for in them there is no great demand for refrigeration.
Such, for example, are the eel and all other fishes of serpent-like form.

Fishes also present diversities as regards the mouth. For in some this is placed in front, at the very extremity
of the body, while in others, as the dolphin and the Selachia, it is placed on the under surface; so that these
fishes turn on the back in order to take their food. The purpose of Nature in this was apparently not merely to
provide a means of salvation for other animals, by allowing them opportunity of escape during the time lost
in the act of turning-for all the fishes with this kind of mouth prey on living animals-but also to prevent
these fishes from giving way too much to their gluttonous ravening after food. For had they been able to seize
their prey more easily than they do, they would soon have perished from over-repletion. An additional reason
is that the projecting extremity of the head in these fishes is round and small, and therefore cannot admit of a
wide opening.

Again, even when the mouth is not placed on the under surface, there are differences in the extent to which it
can open. For in some cases it can gape widely, while in others it is set at the point of a small tapering snout;
the former being the case in carnivorous fishes, such as those with sharp interfitting teeth, whose strength lies
in their mouth, while the latter is its form in all such as are not carnivorous.

The skin is in some fishes covered with scales (the scale of a fish is a thin and shiny film, and therefore easily
becomes detached from the surface of the body). In others it is rough, as for instance in the Rhine, the Batos,
and the like. Fewest of all are those whose skin is smooth. The Selachia have no scales, but a rough skin. This
is explained by their cartilaginous skeleton. For the earthy material which has been thence diverted is
expended by nature upon the skin.

13 73

ON THE PARTS OF ANIMALS

No fish has testicles either externally or internally; as indeed have no apodous animals, among which of
course are included the serpents. One and the same orifice serves both for the excrement and for the
generative secretions, as is the case also in all other oviparous animals, whether two-footed or four-footed,
inasmuch as they have no urinary bladder and form no fluid excretion.

Such then are the characters which distinguish fishes from all other animals. But dolphins and whales and all
such Cetacea are without gills; and, having a lung, are provided with a blow-hole; for this serves them to
discharge the sea-water which has been taken into the mouth. For, feeding as they do in the water, they
cannot but let this fluid enter into their mouth, and, having let it in, they must of necessity let it out again. The
use of gills, however, as has been explained in the treatise on Respiration, is limited to such animals as do not
breathe; for no animal can possibly possess gills and at the same time be a respiratory animal. In order,
therefore, that these Cetacea may discharge the water, they are provided with a blow-hole. This is placed in
front of the brain; for otherwise it would have cut off the brain from the spine. The reason for these animals
having a lung and breathing, is that animals of large size require an excess of heat, to facilitate their motion.
A lung, therefore, is placed within their body, and is fully supplied with blood-heat. These creatures are after
a fashion land and water animals in one. For so far as they are inhalers of air they resemble land-animals,
while they resemble water-animals in having no feet and in deriving their food from the sea. So also seals lie
halfway between land and water animals, and bats half-way between animals that live on the ground and
animals that fly; and so belong to both kinds or to neither. For seals, if looked on as water-animals, are yet
found to have feet; and, if looked on as land-animals, are yet found to have fins. For their hind feet are
exactly like the fins of fishes; and their teeth also are sharp and interfitting as in fishes. Bats again, if regarded
as winged animals, have feet; and, if regarded as quadrupeds, are without them. So also they have neither the
tail of a quadruped nor the tail of a bird; no quadruped's tail, because they are winted animals; no bird's tail,
because they are terrestrial. This absence of tail is the result of necessity. For bats fly by means of a
membrane, but no animal, unless it has barbed feathers, has the tail of a bird; for a bird's tail is composed of
such feathers. As for a quadruped's tail, it would be an actual impediment, if present among the feathers.

Much the same may be said also of the Libyan ostrich. For it has some of the characters of a bird, some of the
characters of a quadruped. It differs from a quadruped in being feathered; and from a bird in being unable to
soar aloft and in having feathers that resemble hair and are useless for flight. Again, it agrees with
quadrupeds in having upper eyelashes, which are the more richly supplied with hairs because the parts about
the head and the upper portion of the neck are bare; and it agrees with birds in being feathered in all the parts
posterior to these. Further, it resembles a bird in being a biped, and a quadruped in having a cloven hoof; for
it has hoofs and not toes. The explanation of these peculiarities is to be found in its bulk, which is that of a
quadruped rather than that of a bird. For, speaking generally, a bird must necessarily be of very small size.
For a body of heavy bulk can with difficulty be raised into the air.

Thus much then as regards the parts of animals. We have discussed them all, and set forth the cause why each
exists; and in so doing we have severally considered each group of animals. We must now pass on, and in due
sequence must next deal with the question of their generation.

-THE END-

14 74

PHYSICS

by Aristotle

PHYSICS

Table of Contents

PHYSICS. 1

by Aristotle 1

Book 1 2

_1 2

2 3

A 5

A 6

_5 8

6 9

1_ 10

_8 12

_9 13

Book II . 14

_1 14

2 15

_3 16

A 18

_5 19

_6 20

J 21

_8 22

9. 23

Book III 24

_1 24

2 26

3. 26

A 27

5. 29

_6 32

1_ 34

_8 35

Book IV 35

A 35

2 37

_3 38

A 39

_5 41

6 42

2 44

_8 45

9. 47

AQ 49

11 50

12 52

13 53

14 55

Book V. 56

1 56

PHYSICS

Table of Contents

2 58

_2 60

_4 61

_5 63

6 64

Book VI 65

J. 65

2 67

3. 69

A 70

_5 71

6 73

1_ 74

1 75

_9 77

JO 78

Book VII 79

_1 79

2 81

3. 83

A 84

5. 87

Book VIII 88

1 88

2 90

3. 91

A 93

_5 95

_6 98

2 100

_8 102

_9 106

10 107

PHYSICS

by Aristotle

translated by R. P. Hardie and R. K. Gaye

• Book I

• 1

• 2

• 3

•4

•5

•6

•7

•8

•9

• Book II

• 1

• 2

•3

•4

•5

•6

•7

•8

•2

• Book III

• 1

• 2

•3

•4

•5

•6

•7

•8

• Book IV

• 1

•2

•3

•4

•5

•6

•7

•8

•9

PHYSICS

• 10

•ii

•12

•13

• 14

• Book V

• 1

• 2

• 3

•4

•5

•6

• Book VI

• 1

•2

•3

•4

•5

•6

•7

•8

•9

• 10

• Book VII

• 1

• 2

•3

•4

•5

• Book VIII

• 1

• 2

• 3

•4

•5

•6

•7

•8

•9

• 10

Book I

WHEN the objects of an inquiry, in any department, have principles, conditions, or elements, it is through
acquaintance with these that knowledge, that is to say scientific knowledge, is attained. For we do not think
that we know a thing until we are acquainted with its primary conditions or first principles, and have carried

Book I 2

PHYSICS

our analysis as far as its simplest elements. Plainly therefore in the science of Nature, as in other branches of
study, our first task will be to try to determine what relates to its principles.

The natural way of doing this is to start from the things which are more knowable and obvious to us and
proceed towards those which are clearer and more knowable by nature; for the same things are not 'knowable
relatively to us' and 'knowable' without qualification. So in the present inquiry we must follow this method
and advance from what is more obscure by nature, but clearer to us, towards what is more clear and more
knowable by nature.

Now what is to us plain and obvious at first is rather confused masses, the elements and principles of which
become known to us later by analysis. Thus we must advance from generalities to particulars; for it is a whole
that is best known to sense-perception, and a generality is a kind of whole, comprehending many things
within it, like parts. Much the same thing happens in the relation of the name to the formula. A name, e.g.
'round', means vaguely a sort of whole: its definition analyses this into its particular senses. Similarly a child
begins by calling all men 'father', and all women 'mother', but later on distinguishes each of them.

The principles in question must be either (a) one or (b) more than one. If (a) one, it must be either (i)
motionless, as Parmenides and Melissus assert, or (ii) in motion, as the physicists hold, some declaring air to
be the first principle, others water. If (b) more than one, then either (i) a finite or (ii) an infinite plurality. If (i)
finite (but more than one), then either two or three or four or some other number. If (ii) infinite, then either as
Democritus believed one in kind, but differing in shape or form; or different in kind and even contrary.

A similar inquiry is made by those who inquire into the number of existents: for they inquire whether the
ultimate constituents of existing things are one or many, and if many, whether a finite or an infinite plurality.
So they too are inquiring whether the principle or element is one or many.

Now to investigate whether Being is one and motionless is not a contribution to the science of Nature. For
just as the geometer has nothing more to say to one who denies the principles of his science-this being a
question for a different science or for or common to all-so a man investigating principles cannot argue with
one who denies their existence. For if Being is just one, and one in the way mentioned, there is a principle no
longer, since a principle must be the principle of some thing or things.

To inquire therefore whether Being is one in this sense would be like arguing against any other position
maintained for the sake of argument (such as the Heraclitean thesis, or such a thesis as that Being is one man)
or like refuting a merely contentious argument-a description which applies to the arguments both of Melissus
and of Parmenides: their premisses are false and their conclusions do not follow. Or rather the argument of
Melissus is gross and palpable and offers no difficulty at all: accept one ridiculous proposition and the rest
follows-a simple enough proceeding.

We physicists, on the other hand, must take for granted that the things that exist by nature are, either all or
some of them, in motion which is indeed made plain by induction. Moreover, no man of science is bound to
solve every kind of difficulty that may be raised, but only as many as are drawn falsely from the principles of
the science: it is not our business to refute those that do not arise in this way: just as it is the duty of the
geometer to refute the squaring of the circle by means of segments, but it is not his duty to refute Antiphon's
proof. At the same time the holders of the theory of which we are speaking do incidentally raise physical
questions, though Nature is not their subject: so it will perhaps be as well to spend a few words on them,
especially as the inquiry is not without scientific interest.

PHYSICS

The most pertinent question with which to begin will be this: In what sense is it asserted that all things are
one? For 'is' is used in many senses. Do they mean that all things 'are' substance or quantities or qualities?
And, further, are all things one substance-one man, one horse, or one soul-or quality and that one and the
same-white or hot or something of the kind? These are all very different doctrines and all impossible to
maintain.

For if both substance and quantity and quality are, then, whether these exist independently of each other or
not, Being will be many.

If on the other hand it is asserted that all things are quality or quantity, then, whether substance exists or not,
an absurdity results, if the impossible can properly be called absurd. For none of the others can exist
independently: substance alone is independent: for everything is predicated of substance as subject. Now
Melissus says that Being is infinite. It is then a quantity. For the infinite is in the category of quantity,
whereas substance or quality or affection cannot be infinite except through a concomitant attribute, that is, if
at the same time they are also quantities. For to define the infinite you must use quantity in your formula, but
not substance or quality. If then Being is both substance and quantity, it is two, not one: if only substance, it
is not infinite and has no magnitude; for to have that it will have to be a quantity.

Again, 'one' itself, no less than 'being', is used in many senses, so we must consider in what sense the word is
used when it is said that the All is one.

Now we say that (a) the continuous is one or that (b) the indivisible is one, or (c) things are said to be 'one',
when their essence is one and the same, as 'liquor' and 'drink'.

If (a) their One is one in the sense of continuous, it is many, for the continuous is divisible ad infinitum.

There is, indeed, a difficulty about part and whole, perhaps not relevant to the present argument, yet
deserving consideration on its own account-namely, whether the part and the whole are one or more than
one, and how they can be one or many, and, if they are more than one, in what sense they are more than one.
(Similarly with the parts of wholes which are not continuous.) Further, if each of the two parts is indivisibly
one with the whole, the difficulty arises that they will be indivisibly one with each other also.

But to proceed: If (b) their One is one as indivisible, nothing will have quantity or quality, and so the one will
not be infinite, as Melissus says-nor, indeed, limited, as Parmenides says, for though the limit is indivisible,
the limited is not.

But if (c) all things are one in the sense of having the same definition, like 'raiment' and 'dress', then it turns
out that they are maintaining the Heraclitean doctrine, for it will be the same thing 'to be good' and 'to be bad',
and 'to be good' and 'to be not good', and so the same thing will be 'good' and 'not good', and man and horse;
in fact, their view will be, not that all things are one, but that they are nothing; and that 'to be of
such-and-such a quality' is the same as 'to be of such-and-such a size'.

Even the more recent of the ancient thinkers were in a pother lest the same thing should turn out in their
hands both one and many. So some, like Lycophron, were led to omit 'is', others to change the mode of
expression and say 'the man has been whitened' instead of 'is white', and 'walks' instead of 'is walking', for
fear that if they added the word 'is' they should be making the one to be many-as if 'one' and 'being' were
always used in one and the same sense. What 'is' may be many either in definition (for example 'to be white'
is one thing, 'to be musical' another, yet the same thing be both, so the one is many) or by division, as the
whole and its parts. On this point, indeed, they were already getting into difficulties and admitted that the one
was many-as if there was any difficulty about the same thing being both one and many, provided that these
are not opposites; for 'one' may mean either 'potentially one' or 'actually one'.

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If, then, we approach the thesis in this way it seems impossible for all things to be one. Further, the
arguments they use to prove their position are not difficult to expose. For both of them reason contentiously-I
mean both Melissus and Parmenides. [Their premisses are false and their conclusions do not follow. Or rather
the argument of Melissus is gross and palpable and offers no difficulty at all: admit one ridiculous
proposition and the rest follows-a simple enough proceeding.] The fallacy of Melissus is obvious. For he
supposes that the assumption 'what has come into being always has a beginning' justifies the assumption
'what has not come into being has no beginning'. Then this also is absurd, that in every case there should be a
beginning of the thing-not of the time and not only in the case of coming to be in the full sense but also in the
case of coming to have a quality-as if change never took place suddenly. Again, does it follow that Being, if
one, is motionless? Why should it not move, the whole of it within itself, as parts of it do which are unities,
e.g. this water? Again, why is qualitative change impossible? But, further, Being cannot be one in form,
though it may be in what it is made of. (Even some of the physicists hold it to be one in the latter way, though
not in the former.) Man obviously differs from horse in form, and contraries from each other.

The same kind of argument holds good against Parmenides also, besides any that may apply specially to his
view: the answer to him being that 'this is not true' and 'that does not follow'. His assumption that one is used
in a single sense only is false, because it is used in several. His conclusion does not follow, because if we take
only white things, and if 'white' has a single meaning, none the less what is white will be many and not one.
For what is white will not be one either in the sense that it is continuous or in the sense that it must be defined
in only one way. 'Whiteness' will be different from 'what has whiteness'. Nor does this mean that there is
anything that can exist separately, over and above what is white. For 'whiteness' and 'that which is white'
differ in definition, not in the sense that they are things which can exist apart from each other. But
Parmenides had not come in sight of this distinction.

It is necessary for him, then, to assume not only that 'being' has the same meaning, of whatever it is
predicated, but further that it means (1) what just is and (2) what is just one.

It must be so, for (1) an attribute is predicated of some subject, so that the subject to which 'being' is
attributed will not be, as it is something different from 'being'. Something, therefore, which is not will be.
Hence 'substance' will not be a predicate of anything else. For the subject cannot be a being, unless 'being'
means several things, in such a way that each is something. But ex hypothesi 'being' means only one thing.

If, then, 'substance' is not attributed to anything, but other things are attributed to it, how does 'substance'
mean what is rather than what is not? For suppose that 'substance' is also 'white'. Since the definition of the
latter is different (for being cannot even be attributed to white, as nothing is which is not 'substance'), it
follows that 'white' is not-being — and that not in the sense of a particular not-being, but in the sense that it is
not at all. Hence 'substance' is not; for it is true to say that it is white, which we found to mean not-being. If
to avoid this we say that even 'white' means substance, it follows that 'being' has more than one meaning.

In particular, then, Being will not have magnitude, if it is substance. For each of the two parts must he in a
different sense.

(2) Substance is plainly divisible into other substances, if we consider the mere nature of a definition. For
instance, if 'man' is a substance, 'animal' and 'biped' must also be substances. For if not substances, they must
be attributes-and if attributes, attributes either of (a) man or of (b) some other subject. But neither is possible.

(a) An attribute is either that which may or may not belong to the subject or that in whose definition the
subject of which it is an attribute is involved. Thus 'sitting' is an example of a separable attribute, while

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'snubness' contains the definition of 'nose', to which we attribute snubness. Further, the definition of the
whole is not contained in the definitions of the contents or elements of the definitory formula; that of 'man'
for instance in 'biped', or that of 'white man' in 'white'. If then this is so, and if 'biped' is supposed to be an
attribute of 'man', it must be either separable, so that 'man' might possibly not be 'biped', or the definition of
'man' must come into the definition of 'biped'-which is impossible, as the converse is the case.

(b) If, on the other hand, we suppose that 'biped' and 'animal' are attributes not of man but of something else,
and are not each of them a substance, then 'man' too will be an attribute of something else. But we must
assume that substance is not the attribute of anything, that the subject of which both 'biped' and 'animal' and
each separately are predicated is the subject also of the complex 'biped animal'.

Are we then to say that the All is composed of indivisible substances? Some thinkers did, in point of fact,
give way to both arguments. To the argument that all things are one if being means one thing, they conceded
that not-being is; to that from bisection, they yielded by positing atomic magnitudes. But obviously it is not
true that if being means one thing, and cannot at the same time mean the contradictory of this, there will be
nothing which is not, for even if what is not cannot be without qualification, there is no reason why it should
not be a particular not-being. To say that all things will be one, if there is nothing besides Being itself, is
absurd. For who understands 'being itself to be anything but a particular substance? But if this is so, there is
nothing to prevent there being many beings, as has been said.

It is, then, clearly impossible for Being to be one in this sense.

The physicists on the other hand have two modes of explanation.

The first set make the underlying body one either one of the three or something else which is denser than fire
and rarer than air then generate everything else from this, and obtain multiplicity by condensation and
rarefaction. Now these are contraries, which may be generalized into 'excess and defect'. (Compare Plato's
'Great and Small'-except that he make these his matter, the one his form, while the others treat the one which
underlies as matter and the contraries as differentiae, i.e. forms).

The second set assert that the contrarieties are contained in the one and emerge from it by segregation, for
example Anaximander and also all those who assert that 'what is' is one and many, like Empedocles and
Anaxagoras; for they too produce other things from their mixture by segregation. These differ, however, from
each other in that the former imagines a cycle of such changes, the latter a single series. Anaxagoras again
made both his 'homceomerous' substances and his contraries infinite in multitude, whereas Empedocles posits
only the so-called elements.

The theory of Anaxagoras that the principles are infinite in multitude was probably due to his acceptance of
the common opinion of the physicists that nothing comes into being from not-being. For this is the reason
why they use the phrase 'all things were together' and the coming into being of such and such a kind of thing
is reduced to change of quality, while some spoke of combination and separation. Moreover, the fact that the
contraries proceed from each other led them to the conclusion. The one, they reasoned, must have already
existed in the other; for since everything that comes into being must arise either from what is or from what is
not, and it is impossible for it to arise from what is not (on this point all the physicists agree), they thought
that the truth of the alternative necessarily followed, namely that things come into being out of existent
things, i.e. out of things already present, but imperceptible to our senses because of the smallness of their
bulk. So they assert that everything has been mixed in every, thing, because they saw everything arising out
of everything. But things, as they say, appear different from one another and receive different names

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according to the nature of the particles which are numerically predominant among the innumerable
constituents of the mixture. For nothing, they say, is purely and entirely white or black or sweet, bone or
flesh, but the nature of a thing is held to be that of which it contains the most.

Now (1) the infinite qua infinite is unknowable, so that what is infinite in multitude or size is unknowable in
quantity, and what is infinite in variety of kind is unknowable in quality. But the principles in question are
infinite both in multitude and in kind. Therefore it is impossible to know things which are composed of them;
for it is when we know the nature and quantity of its components that we suppose we know a complex.

Further (2) if the parts of a whole may be of any size in the direction either of greatness or of smallness (by
'parts' I mean components into which a whole can be divided and which are actually present in it), it is
necessary that the whole thing itself may be of any size. Clearly, therefore, since it is impossible for an
animal or plant to be indefinitely big or small, neither can its parts be such, or the whole will be the same. But
flesh, bone, and the like are the parts of animals, and the fruits are the parts of plants. Hence it is obvious that
neither flesh, bone, nor any such thing can be of indefinite size in the direction either of the greater or of the
less.

Again (3) according to the theory all such things are already present in one another and do not come into
being but are constituents which are separated out, and a thing receives its designation from its chief
constituent. Further, anything may come out of anything-water by segregation from flesh and flesh from
water. Hence, since every finite body is exhausted by the repeated abstraction of a finite body, it seems
obviously to follow that everything cannot subsist in everything else. For let flesh be extracted from water
and again more flesh be produced from the remainder by repeating the process of separation: then, even
though the quantity separated out will continually decrease, still it will not fall below a certain magnitude. If,
therefore, the process comes to an end, everything will not be in everything else (for there will be no flesh in
the remaining water); if on the other hand it does not, and further extraction is always possible, there will be
an infinite multitude of finite equal particles in a finite quantity-which is impossible. Another proof may be
added: Since every body must diminish in size when something is taken from it, and flesh is quantitatively
definite in respect both of greatness and smallness, it is clear that from the minimum quantity of flesh no
body can be separated out; for the flesh left would be less than the minimum of flesh.

Lastly (4) in each of his infinite bodies there would be already present infinite flesh and blood and brain-
having a distinct existence, however, from one another, and no less real than the infinite bodies, and each
infinite: which is contrary to reason.

The statement that complete separation never will take place is correct enough, though Anaxagoras is not
fully aware of what it means. For affections are indeed inseparable. If then colours and states had entered into
the mixture, and if separation took place, there would be a 'white' or a 'healthy' which was nothing but white
or healthy, i.e. was not the predicate of a subject. So his 'Mind' is an absurd person aiming at the impossible,
if he is supposed to wish to separate them, and it is impossible to do so, both in respect of quantity and of
quality- of quantity, because there is no minimum magnitude, and of quality, because affections are
inseparable.

Nor is Anaxagoras right about the coming to be of homogeneous bodies. It is true there is a sense in which
clay is divided into pieces of clay, but there is another in which it is not. Water and air are, and are generated
'from' each other, but not in the way in which bricks come 'from' a house and again a house 'from' bricks; and
it is better to assume a smaller and finite number of principles, as Empedocles does.

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All thinkers then agree in making the contraries principles, both those who describe the All as one and
unmoved (for even Parmenides treats hot and cold as principles under the names of fire and earth) and those
too who use the rare and the dense. The same is true of Democritus also, with his plenum and void, both of
which exist, be says, the one as being, the other as not-being. Again he speaks of differences in position,
shape, and order, and these are genera of which the species are contraries, namely, of position, above and
below, before and behind; of shape, angular and angle-less, straight and round.

It is plain then that they all in one way or another identify the contraries with the principles. And with good
reason. For first principles must not be derived from one another nor from anything else, while everything has
to be derived from them. But these conditions are fulfilled by the primary contraries, which are not derived
from anything else because they are primary, nor from each other because they are contraries.

But we must see how this can be arrived at as a reasoned result, as well as in the way just indicated.

Our first presupposition must be that in nature nothing acts on, or is acted on by, any other thing at random,
nor may anything come from anything else, unless we mean that it does so in virtue of a concomitant
attribute. For how could 'white' come from 'musical', unless 'musical' happened to be an attribute of the
not-white or of the black? No, 'white' comes from 'not-white'-and not from any 'not-white', but from black
or some intermediate colour. Similarly, 'musical' comes to be from 'not-musical', but not from any thing
other than musical, but from 'unmusical' or any intermediate state there may be.

Nor again do things pass into the first chance thing; 'white' does not pass into 'musical' (except, it may be, in
virtue of a concomitant attribute), but into 'not-white'-and not into any chance thing which is not white, but
into black or an intermediate colour; 'musical' passes into 'not-musical'-and not into any chance thing other
than musical, but into 'unmusical' or any intermediate state there may be.

The same holds of other things also: even things which are not simple but complex follow the same principle,
but the opposite state has not received a name, so we fail to notice the fact. What is in tune must come from
what is not in tune, and vice versa; the tuned passes into untunedness-and not into any untunedness, but into
the corresponding opposite. It does not matter whether we take attunement, order, or composition for our
illustration; the principle is obviously the same in all, and in fact applies equally to the production of a house,
a statue, or any other complex. A house comes from certain things in a certain state of separation instead of
conjunction, a statue (or any other thing that has been shaped) from shapelessness-each of these objects
being partly order and partly composition.

If then this is true, everything that comes to be or passes away from, or passes into, its contrary or an
intermediate state. But the intermediates are derived from the contraries-colours, for instance, from black and
white. Everything, therefore, that comes to be by a natural process is either a contrary or a product of
contraries.

Up to this point we have practically had most of the other writers on the subject with us, as I have said
already: for all of them identify their elements, and what they call their principles, with the contraries, giving
no reason indeed for the theory, but contrained as it were by the truth itself. They differ, however, from one
another in that some assume contraries which are more primary, others contraries which are less so: some
those more knowable in the order of explanation, others those more familiar to sense. For some make hot and
cold, or again moist and dry, the conditions of becoming; while others make odd and even, or again Love and
Strife; and these differ from each other in the way mentioned.

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Hence their principles are in one sense the same, in another different; different certainly, as indeed most
people think, but the same inasmuch as they are analogous; for all are taken from the same table of columns,
some of the pairs being wider, others narrower in extent. In this way then their theories are both the same and
different, some better, some worse; some, as I have said, take as their contraries what is more knowable in the
order of explanation, others what is more familiar to sense. (The universal is more knowable in the order of
explanation, the particular in the order of sense: for explanation has to do with the universal, sense with the
particular.) 'The great and the small', for example, belong to the former class, 'the dense and the rare' to the
latter.

It is clear then that our principles must be contraries.

The next question is whether the principles are two or three or more in number.

One they cannot be, for there cannot be one contrary. Nor can they be innumerable, because, if so, Being will
not be knowable: and in any one genus there is only one contrariety, and substance is one genus: also a finite
number is sufficient, and a finite number, such as the principles of Empedocles, is better than an infinite
multitude; for Empedocles professes to obtain from his principles all that Anaxagoras obtains from his
innumerable principles. Lastly, some contraries are more primary than others, and some arise from others-for
example sweet and bitter, white and black-whereas the principles must always remain principles.

This will suffice to show that the principles are neither one nor innumerable.

Granted, then, that they are a limited number, it is plausible to suppose them more than two. For it is difficult
to see how either density should be of such a nature as to act in any way on rarity or rarity on density. The
same is true of any other pair of contraries; for Love does not gather Strife together and make things out of it,
nor does Strife make anything out of Love, but both act on a third thing different from both. Some indeed
assume more than one such thing from which they construct the world of nature.

Other objections to the view that it is not necessary to assume a third principle as a substratum may be added.
(1) We do not find that the contraries constitute the substance of any thing. But what is a first principle ought
not to be the predicate of any subject. If it were, there would be a principle of the supposed principle: for the
subject is a principle, and prior presumably to what is predicated of it. Again (2) we hold that a substance is
not contrary to another substance. How then can substance be derived from what are not substances? Or how
can non-substances be prior to substance?

If then we accept both the former argument and this one, we must, to preserve both, assume a third somewhat
as the substratum of the contraries, such as is spoken of by those who describe the All as one nature-water or
fire or what is intermediate between them. What is intermediate seems preferable; for fire, earth, air, and
water are already involved with pairs of contraries. There is, therefore, much to be said for those who make
the underlying substance different from these four; of the rest, the next best choice is air, as presenting
sensible differences in a less degree than the others; and after air, water. All, however, agree in this, that they
differentiate their One by means of the contraries, such as density and rarity and more and less, which may of
course be generalized, as has already been said into excess and defect. Indeed this doctrine too (that the One
and excess and defect are the principles of things) would appear to be of old standing, though in different
forms; for the early thinkers made the two the active and the one the passive principle, whereas some of the
more recent maintain the reverse.

To suppose then that the elements are three in number would seem, from these and similar considerations, a

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plausible view, as I said before. On the other hand, the view that they are more than three in number would
seem to be untenable.

For the one substratum is sufficient to be acted on; but if we have four contraries, there will be two
contrarieties, and we shall have to suppose an intermediate nature for each pair separately. If, on the other
hand, the contrarieties, being two, can generate from each other, the second contrariety will be superfluous.
Moreover, it is impossible that there should be more than one primary contrariety. For substance is a single
genus of being, so that the principles can differ only as prior and posterior, not in genus; in a single genus
there is always a single contrariety, all the other contrarieties in it being held to be reducible to one.

It is clear then that the number of elements is neither one nor more than two or three; but whether two or
three is, as I said, a question of considerable difficulty.

We will now give our own account, approaching the question first with reference to becoming in its widest
sense: for we shall be following the natural order of inquiry if we speak first of common characteristics, and
then investigate the characteristics of special cases.

We say that one thing comes to be from another thing, and one sort of thing from another sort of thing, both
in the case of simple and of complex things. I mean the following. We can say (1) 'man becomes musical', (2)
what is 'not-musical becomes musical', or (3), the 'not-musical man becomes a musical man'. Now what
becomes in (1) and (2)-'man' and 'not musical'-I call simple, and what each becomes-'musical'-simple also.
But when (3) we say the 'not-musical man becomes a musical man', both what becomes and what it becomes
are complex.

As regards one of these simple 'things that become' we say not only 'this becomes so-and-so', but also 'from
being this, comes to be so-and-so', as 'from being not-musical comes to be musical'; as regards the other we
do not say this in all cases, as we do not say (1) 'from being a man he came to be musical' but only 'the man
became musical'.

When a 'simple' thing is said to become something, in one case (1) it survives through the process, in the
other (2) it does not. For man remains a man and is such even when he becomes musical, whereas what is not
musical or is unmusical does not continue to exist, either simply or combined with the subject.

These distinctions drawn, one can gather from surveying the various cases of becoming in the way we are
describing that, as we say, there must always be an underlying something, namely that which becomes, and
that this, though always one numerically, in form at least is not one. (By that I mean that it can be described
in different ways.) For 'to be man' is not the same as 'to be unmusical'. One part survives, the other does not:
what is not an opposite survives (for 'man' survives), but 'not-musical' or 'unmusical' does not survive, nor
does the compound of the two, namely 'unmusical man'.

We speak of 'becoming that from this' instead of 'this becoming that' more in the case of what does not
survive the change- 'becoming musical from unmusical', not 'from man'-but there are exceptions, as we
sometimes use the latter form of expression even of what survives; we speak of 'a statue coming to be from
bronze', not of the 'bronze becoming a statue'. The change, however, from an opposite which does not survive
is described indifferently in both ways, 'becoming that from this' or 'this becoming that'. We say both that 'the
unmusical becomes musical', and that 'from unmusical he becomes musical'. And so both forms are used of
the complex, 'becoming a musical man from an unmusical man', and unmusical man becoming a musical
man'.

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But there are different senses of 'coming to be'. In some cases we do not use the expression 'come to be', but
'come to be so-and-so'. Only substances are said to 'come to be' in the unqualified sense.

Now in all cases other than substance it is plain that there must be some subject, namely, that which becomes.
For we know that when a thing comes to be of such a quantity or quality or in such a relation, time, or place,
a subject is always presupposed, since substance alone is not predicated of another subject, but everything
else of substance.

But that substances too, and anything else that can be said 'to be' without qualification, come to be from some
substratum, will appear on examination. For we find in every case something that underlies from which
proceeds that which comes to be; for instance, animals and plants from seed.

Generally things which come to be, come to be in different ways: (1) by change of shape, as a statue; (2) by
addition, as things which grow; (3) by taking away, as the Hermes from the stone; (4) by putting together, as
a house; (5) by alteration, as things which 'turn' in respect of their material substance.

It is plain that these are all cases of coming to be from a substratum.

Thus, clearly, from what has been said, whatever comes to be is always complex. There is, on the one hand,
(a) something which comes into existence, and again (b) something which becomes that-the latter (b) in two
senses, either the subject or the opposite. By the 'opposite' I mean the 'unmusical', by the 'subject' 'man', and
similarly I call the absence of shape or form or order the 'opposite', and the bronze or stone or gold the
'subject'.

Plainly then, if there are conditions and principles which constitute natural objects and from which they
primarily are or have come to be-have come to be, I mean, what each is said to be in its essential nature, not
what each is in respect of a concomitant attribute-plainly, I say, everything comes to be from both subject
and form. For 'musical man' is composed (in a way) of 'man' and 'musical': you can analyse it into the
definitions of its elements. It is clear then that what comes to be will come to be from these elements.

Now the subject is one numerically, though it is two in form. (For it is the man, the gold-the 'matter'
generally-that is counted, for it is more of the nature of a 'this', and what comes to be does not come from it
in virtue of a concomitant attribute; the privation, on the other hand, and the contrary are incidental in the
process.) And the positive form is one-the order, the acquired art of music, or any similar predicate.

There is a sense, therefore, in which we must declare the principles to be two, and a sense in which they are
three; a sense in which the contraries are the principles-say for example the musical and the unmusical, the
hot and the cold, the tuned and the untuned-and a sense in which they are not, since it is impossible for the
contraries to be acted on by each other. But this difficulty also is solved by the fact that the substratum is
different from the contraries, for it is itself not a contrary. The principles therefore are, in a way, not more in
number than the contraries, but as it were two, nor yet precisely two, since there is a difference of essential
nature, but three. For 'to be man' is different from 'to be unmusical', and 'to be unformed' from 'to be bronze'.

We have now stated the number of the principles of natural objects which are subject to generation, and how
the number is reached: and it is clear that there must be a substratum for the contraries, and that the contraries
must be two. (Yet in another way of putting it this is not necessary, as one of the contraries will serve to
effect the change by its successive absence and presence.)

The underlying nature is an object of scientific knowledge, by an analogy. For as the bronze is to the statue,
the wood to the bed, or the matter and the formless before receiving form to any thing which has form, so is
the underlying nature to substance, i.e. the 'this' or existent.

7 11

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This then is one principle (though not one or existent in the same sense as the 'this'), and the definition was
one as we agreed; then further there is its contrary, the privation. In what sense these are two, and in what
sense more, has been stated above. Briefly, we explained first that only the contraries were principles, and
later that a substratum was indispensable, and that the principles were three; our last statement has elucidated
the difference between the contraries, the mutual relation of the principles, and the nature of the substratum.
Whether the form or the substratum is the essential nature of a physical object is not yet clear. But that the
principles are three, and in what sense, and the way in which each is a principle, is clear.

So much then for the question of the number and the nature of the principles.

We will now proceed to show that the difficulty of the early thinkers, as well as our own, is solved in this
way alone.

The first of those who studied science were misled in their search for truth and the nature of things by their
inexperience, which as it were thrust them into another path. So they say that none of the things that are either
comes to be or passes out of existence, because what comes to be must do so either from what is or from what
is not, both of which are impossible. For what is cannot come to be (because it is already), and from what is
not nothing could have come to be (because something must be present as a substratum). So too they
exaggerated the consequence of this, and went so far as to deny even the existence of a plurality of things,
maintaining that only Being itself is. Such then was their opinion, and such the reason for its adoption.

Our explanation on the other hand is that the phrases 'something comes to be from what is or from what is
not', 'what is not or what is does something or has something done to it or becomes some particular thing', are
to be taken (in the first way of putting our explanation) in the same sense as 'a doctor does something or has
something done to him', 'is or becomes something from being a doctor.' These expressions may be taken in
two senses, and so too, clearly, may 'from being', and 'being acts or is acted on'. A doctor builds a house, not
qua doctor, but qua housebuilder, and turns gray, not qua doctor, but qua dark-haired. On the other hand he
doctors or fails to doctor qua doctor. But we are using words most appropriately when we say that a doctor
does something or undergoes something, or becomes something from being a doctor, if he does, undergoes,
or becomes qua doctor. Clearly then also 'to come to be so-and-so from not-being' means 'qua not-being'.

It was through failure to make this distinction that those thinkers gave the matter up, and through this error
that they went so much farther astray as to suppose that nothing else comes to be or exists apart from Being
itself, thus doing away with all becoming.

We ourselves are in agreement with them in holding that nothing can be said without qualification to come
from what is not. But nevertheless we maintain that a thing may 'come to be from what is not'-that is, in a
qualified sense. For a thing comes to be from the privation, which in its own nature is not-being,-this not
surviving as a constituent of the result. Yet this causes surprise, and it is thought impossible that something
should come to be in the way described from what is not.

In the same way we maintain that nothing comes to be from being, and that being does not come to be except
in a qualified sense. In that way, however, it does, just as animal might come to be from animal, and an
animal of a certain kind from an animal of a certain kind. Thus, suppose a dog to come to be from a horse.
The dog would then, it is true, come to be from animal (as well as from an animal of a certain kind) but not as
animal, for that is already there. But if anything is to become an animal, not in a qualified sense, it will not be
from animal: and if being, not from being-nor from not-being either, for it has been explained that by 'from
not being' we mean from not-being qua not-being.

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Note further that we do not subvert the principle that everything either is or is not.

This then is one way of solving the difficulty. Another consists in pointing out that the same things can be
explained in terms of potentiality and actuality. But this has been done with greater precision elsewhere. So,
as we said, the difficulties which constrain people to deny the existence of some of the things we mentioned
are now solved. For it was this reason which also caused some of the earlier thinkers to turn so far aside from
the road which leads to coming to be and passing away and change generally. If they had come in sight of
this nature, all their ignorance would have been dispelled.

Others, indeed, have apprehended the nature in question, but not adequately.

In the first place they allow that a thing may come to be without qualification from not being, accepting on
this point the statement of Parmenides. Secondly, they think that if the substratum is one numerically, it must
have also only a single potentiality-which is a very different thing.

Now we distinguish matter and privation, and hold that one of these, namely the matter, is not-being only in
virtue of an attribute which it has, while the privation in its own nature is not-being; and that the matter is
nearly, in a sense is, substance, while the privation in no sense is. They, on the other hand, identify their
Great and Small alike with not being, and that whether they are taken together as one or separately. Their
triad is therefore of quite a different kind from ours. For they got so far as to see that there must be some
underlying nature, but they make it one-for even if one philosopher makes a dyad of it, which he calls Great
and Small, the effect is the same, for he overlooked the other nature. For the one which persists is a joint
cause, with the form, of what comes to be-a mother, as it were. But the negative part of the contrariety may
often seem, if you concentrate your attention on it as an evil agent, not to exist at all.

For admitting with them that there is something divine, good, and desirable, we hold that there are two other
principles, the one contrary to it, the other such as of its own nature to desire and yearn for it. But the
consequence of their view is that the contrary desires its wtextinction. Yet the form cannot desire itself, for it
is not defective; nor can the contrary desire it, for contraries are mutually destructive. The truth is that what
desires the form is matter, as the female desires the male and the ugly the beautiful-only the ugly or the
female not per se but per accidens.

The matter comes to be and ceases to be in one sense, while in another it does not. As that which contains the
privation, it ceases to be in its own nature, for what ceases to be-the privation-is contained within it. But as
potentiality it does not cease to be in its own nature, but is necessarily outside the sphere of becoming and
ceasing to be. For if it came to be, something must have existed as a primary substratum from which it should
come and which should persist in it; but this is its own special nature, so that it will be before coming to be.
(For my definition of matter is just this-the primary substratum of each thing, from which it comes to be
without qualification, and which persists in the result.) And if it ceases to be it will pass into that at the last,
so it will have ceased to be before ceasing to be.

The accurate determination of the first principle in respect of form, whether it is one or many and what it is or
what they are, is the province of the primary type of science; so these questions may stand over till then. But
of the natural, i.e. perishable, forms we shall speak in the expositions which follow.

The above, then, may be taken as sufficient to establish that there are principles and what they are and how
many there are. Now let us make a fresh start and proceed.

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Book II

Of things that exist, some exist by nature, some from other causes.

'By nature' the animals and their parts exist, and the plants and the simple bodies (earth, fire, air, water)-for
we say that these and the like exist 'by nature'.

All the things mentioned present a feature in which they differ from things which are not constituted by
nature. Each of them has within itself a principle of motion and of stationariness (in respect of place, or of
growth and decrease, or by way of alteration). On the other hand, a bed and a coat and anything else of that
sort, qua receiving these designations i.e. in so far as they are products of art-have no innate impulse to
change. But in so far as they happen to be composed of stone or of earth or of a mixture of the two, they do
have such an impulse, and just to that extent which seems to indicate that nature is a source or cause of being
moved and of being at rest in that to which it belongs primarily, in virtue of itself and not in virtue of a
concomitant attribute.

I say 'not in virtue of a concomitant attribute', because (for instance) a man who is a doctor might cure
himself. Nevertheless it is not in so far as he is a patient that he possesses the art of medicine: it merely has
happened that the same man is doctor and patient-and that is why these attributes are not always found
together. So it is with all other artificial products. None of them has in itself the source of its own production.
But while in some cases (for instance houses and the other products of manual labour) that principle is in
something else external to the thing, in others those which may cause a change in themselves in virtue of a
concomitant attribute-it lies in the things themselves (but not in virtue of what they are).

'Nature' then is what has been stated. Things 'have a nature'which have a principle of this kind. Each of them
is a substance; for it is a subject, and nature always implies a subject in which it inheres.

The term 'according to nature' is applied to all these things and also to the attributes which belong to them in
virtue of what they are, for instance the property of fire to be carried upwards-which is not a 'nature' nor 'has
a nature' but is 'by nature' or 'according to nature'.

What nature is, then, and the meaning of the terms 'by nature' and 'according to nature', has been stated. That
nature exists, it would be absurd to try to prove; for it is obvious that there are many things of this kind, and
to prove what is obvious by what is not is the mark of a man who is unable to distinguish what is self-evident
from what is not. (This state of mind is clearly possible. A man blind from birth might reason about colours.
Presumably therefore such persons must be talking about words without any thought to correspond.)

Some identify the nature or substance of a natural object with that immediate constituent of it which taken by
itself is without arrangement, e.g. the wood is the 'nature' of the bed, and the bronze the 'nature' of the statue.

As an indication of this Antiphon points out that if you planted a bed and the rotting wood acquired the power
of sending up a shoot, it would not be a bed that would come up, but wood-which shows that the
arrangement in accordance with the rules of the art is merely an incidental attribute, whereas the real nature is
the other, which, further, persists continuously through the process of making.

But if the material of each of these objects has itself the same relation to something else, say bronze (or gold)
to water, bones (or wood) to earth and so on, that (they say) would be their nature and essence. Consequently
some assert earth, others fire or air or water or some or all of these, to be the nature of the things that are. For

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whatever any one of them supposed to have this character-whether one thing or more than one thing-this or
these he declared to be the whole of substance, all else being its affections, states, or dispositions. Every such
thing they held to be eternal (for it could not pass into anything else), but other things to come into being and
cease to be times without number.

This then is one account of 'nature', namely that it is the immediate material substratum of things which have
in themselves a principle of motion or change.

Another account is that 'nature' is the shape or form which is specified in the definition of the thing.

For the word 'nature' is applied to what is according to nature and the natural in the same way as 'art' is
applied to what is artistic or a work of art. We should not say in the latter case that there is anything artistic
about a thing, if it is a bed only potentially, not yet having the form of a bed; nor should we call it a work of
art. The same is true of natural compounds. What is potentially flesh or bone has not yet its own 'nature', and
does not exist until it receives the form specified in the definition, which we name in defining what flesh or
bone is. Thus in the second sense of 'nature' it would be the shape or form (not separable except in statement)
of things which have in themselves a source of motion. (The combination of the two, e.g. man, is not 'nature'
but 'by nature' or 'natural'.)

The form indeed is 'nature' rather than the matter; for a thing is more properly said to be what it is when it has
attained to fulfilment than when it exists potentially. Again man is born from man, but not bed from bed. That
is why people say that the figure is not the nature of a bed, but the wood is-if the bed sprouted not a bed but
wood would come up. But even if the figure is art, then on the same principle the shape of man is his nature.
For man is born from man.

We also speak of a thing's nature as being exhibited in the process of growth by which its nature is attained.
The 'nature' in this sense is not like 'doctoring', which leads not to the art of doctoring but to health. Doctoring
must start from the art, not lead to it. But it is not in this way that nature (in the one sense) is related to nature
(in the other). What grows qua growing grows from something into something. Into what then does it grow?
Not into that from which it arose but into that to which it tends. The shape then is nature.

'Shape' and 'nature', it should be added, are in two senses. For the privation too is in a way form. But whether
in unqualified coming to be there is privation, i.e. a contrary to what comes to be, we must consider later.

We have distinguished, then, the different ways in which the term 'nature' is used.

The next point to consider is how the mathematician differs from the physicist. Obviously physical bodies
contain surfaces and volumes, lines and points, and these are the subject-matter of mathematics.

Further, is astronomy different from physics or a department of it? It seems absurd that the physicist should
be supposed to know the nature of sun or moon, but not to know any of their essential attributes, particularly
as the writers on physics obviously do discuss their shape also and whether the earth and the world are
spherical or not.

Now the mathematician, though he too treats of these things, nevertheless does not treat of them as the limits
of a physical body; nor does he consider the attributes indicated as the attributes of such bodies. That is why
he separates them; for in thought they are separable from motion, and it makes no difference, nor does any
falsity result, if they are separated. The holders of the theory of Forms do the same, though they are not aware

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of it; for they separate the objects of physics, which are less separable than those of mathematics. This
becomes plain if one tries to state in each of the two cases the definitions of the things and of their attributes.
'Odd' and 'even', 'straight' and 'curved', and likewise 'number', 'line', and 'figure', do not involve motion; not so
'flesh' and 'bone' and 'man'-these are defined like 'snub nose', not like 'curved'.

Similar evidence is supplied by the more physical of the branches of mathematics, such as optics, harmonics,
and astronomy. These are in a way the converse of geometry. While geometry investigates physical lines but
not qua physical, optics investigates mathematical lines, but qua physical, not qua mathematical.

Since 'nature' has two senses, the form and the matter, we must investigate its objects as we would the
essence of snubness. That is, such things are neither independent of matter nor can be defined in terms of
matter only. Here too indeed one might raise a difficulty. Since there are two natures, with which is the
physicist concerned? Or should he investigate the combination of the two? But if the combination of the two,
then also each severally. Does it belong then to the same or to different sciences to know each severally?

If we look at the ancients, physics would to be concerned with the matter. (It was only very slightly that
Empedocles and Democritus touched on the forms and the essence.)

But if on the other hand art imitates nature, and it is the part of the same discipline to know the form and the
matter up to a point (e.g. the doctor has a knowledge of health and also of bile and phlegm, in which health is
realized, and the builder both of the form of the house and of the matter, namely that it is bricks and beams,
and so forth): if this is so, it would be the part of physics also to know nature in both its senses.

Again, 'that for the sake of which', or the end, belongs to the same department of knowledge as the means.
But the nature is the end or 'that for the sake of which'. For if a thing undergoes a continuous change and
there is a stage which is last, this stage is the end or 'that for the sake of which'. (That is why the poet was
carried away into making an absurd statement when he said 'he has the end for the sake of which he was
born'. For not every stage that is last claims to be an end, but only that which is best.)

For the arts make their material (some simply 'make' it, others make it serviceable), and we use everything as
if it was there for our sake. (We also are in a sense an end. 'That for the sake of which' has two senses: the
distinction is made in our work On Philosophy.) The arts, therefore, which govern the matter and have
knowledge are two, namely the art which uses the product and the art which directs the production of it. That
is why the using art also is in a sense directive; but it differs in that it knows the form, whereas the art which
is directive as being concerned with production knows the matter. For the helmsman knows and prescribes
what sort of form a helm should have, the other from what wood it should be made and by means of what
operations. In the products of art, however, we make the material with a view to the function, whereas in the
products of nature the matter is there all along.

Again, matter is a relative term: to each form there corresponds a special matter. How far then must the
physicist know the form or essence? Up to a point, perhaps, as the doctor must know sinew or the smith
bronze (i.e. until he understands the purpose of each): and the physicist is concerned only with things whose
forms are separable indeed, but do not exist apart from matter. Man is begotten by man and by the sun as
well. The mode of existence and essence of the separable it is the business of the primary type of philosophy
to define.

Now that we have established these distinctions, we must proceed to consider causes, their character and
number. Knowledge is the object of our inquiry, and men do not think they know a thing till they have

PHYSICS

grasped the 'why' of (which is to grasp its primary cause). So clearly we too must do this as regards both
coming to be and passing away and every kind of physical change, in order that, knowing their principles, we
may try to refer to these principles each of our problems.

In one sense, then, (1) that out of which a thing comes to be and which persists, is called 'cause', e.g. the
bronze of the statue, the silver of the bowl, and the genera of which the bronze and the silver are species.

In another sense (2) the form or the archetype, i.e. the statement of the essence, and its genera, are called
'causes' (e.g. of the octave the relation of 2:1, and generally number), and the parts in the definition.

Again (3) the primary source of the change or coming to rest; e.g. the man who gave advice is a cause, the
father is cause of the child, and generally what makes of what is made and what causes change of what is
changed.

Again (4) in the sense of end or 'that for the sake of which a thing is done, e.g. health is the cause of walking
about. ('Why is he walking about?' we say. 'To be healthy', and, having said that, we think we have assigned
the cause.) The same is true also of all the intermediate steps which are brought about through the action of
something else as means towards the end, e.g. reduction of flesh, purging, drugs, or surgical instruments are
means towards health. All these things are 'for the sake of the end, though they differ from one another in
that some are activities, others instruments.

This then perhaps exhausts the number of ways in which the term 'cause' is used.

As the word has several senses, it follows that there are several causes of the same thing not merely in virtue
of a concomitant attribute), e.g. both the art of the sculptor and the bronze are causes of the statue. These are
causes of the statue qua statue, not in virtue of anything else that it may be-only not in the same way, the one
being the material cause, the other the cause whence the motion comes. Some things cause each other
reciprocally, e.g. hard work causes fitness and vice versa, but again not in the same way, but the one as end,
the other as the origin of change. Further the same thing is the cause of contrary results. For that which by its
presence brings about one result is sometimes blamed for bringing about the contrary by its absence. Thus we
ascribe the wreck of a ship to the absence of the pilot whose presence was the cause of its safety.

All the causes now mentioned fall into four familiar divisions. The letters are the causes of syllables, the
material of artificial products, fire, of bodies, the parts of the whole, and the premisses of the conclusion, in
the sense of 'that from which'. Of these pairs the one set are causes in the sense of substratum, e.g. the parts,
the other set in the sense of essence-the whole and the combination and the form. But the seed and the doctor
and the adviser, and generally the maker, are all sources whence the change or stationariness originates, while
the others are causes in the sense of the end or the good of the rest; for 'that for the sake of which' means what
is best and the end of the things that lead up to it. (Whether we say the 'good itself or the 'apparent good'
makes no difference.)

Such then is the number and nature of the kinds of cause.

Now the modes of causation are many, though when brought under heads they too can be reduced in number.
For 'cause' is used in many senses and even within the same kind one may be prior to another (e.g. the doctor
and the expert are causes of health, the relation 2:1 and number of the octave), and always what is inclusive
to what is particular. Another mode of causation is the incidental and its genera, e.g. in one way 'Polyclitus',
in another 'sculptor' is the cause of a statue, because 'being Polyclitus' and 'sculptor' are incidentally
conjoined. Also the classes in which the incidental attribute is included; thus 'a man' could be said to be the
cause of a statue or, generally, 'a living creature'. An incidental attribute too may be more or less remote, e.g.
suppose that 'a pale man' or 'a musical man' were said to be the cause of the statue.

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All causes, both proper and incidental, may be spoken of either as potential or as actual; e.g. the cause of a
house being built is either 'house-builder' or 'house-builder building'.

Similar distinctions can be made in the things of which the causes are causes, e.g. of 'this statue' or of 'statue'
or of 'image' generally, of 'this bronze' or of 'bronze' or of 'material' generally. So too with the incidental
attributes. Again we may use a complex expression for either and say, e.g. neither 'Polyclitus' nor 'sculptor'
but 'Polyclitus, sculptor'.

All these various uses, however, come to six in number, under each of which again the usage is twofold.
Cause means either what is particular or a genus, or an incidental attribute or a genus of that, and these either
as a complex or each by itself; and all six either as actual or as potential. The difference is this much, that
causes which are actually at work and particular exist and cease to exist simultaneously with their effect, e.g.
this healing person with this being-healed person and that house-building man with that being-built house;
but this is not always true of potential causes — the house and the housebuilder do not pass away
simultaneously.

In investigating the cause of each thing it is always necessary to seek what is most precise (as also in other
things): thus man builds because he is a builder, and a builder builds in virtue of his art of building. This last
cause then is prior: and so generally.

Further, generic effects should be assigned to generic causes, particular effects to particular causes, e.g. statue
to sculptor, this statue to this sculptor; and powers are relative to possible effects, actually operating causes to
things which are actually being effected.

This must suffice for our account of the number of causes and the modes of causation.

But chance also and spontaneity are reckoned among causes: many things are said both to be and to come to
be as a result of chance and spontaneity. We must inquire therefore in what manner chance and spontaneity
are present among the causes enumerated, and whether they are the same or different, and generally what
chance and spontaneity are.

Some people even question whether they are real or not. They say that nothing happens by chance, but that
everything which we ascribe to chance or spontaneity has some definite cause, e.g. coming 'by chance' into
the market and finding there a man whom one wanted but did not expect to meet is due to one's wish to go
and buy in the market. Similarly in other cases of chance it is always possible, they maintain, to find
something which is the cause; but not chance, for if chance were real, it would seem strange indeed, and the
question might be raised, why on earth none of the wise men of old in speaking of the causes of generation
and decay took account of chance; whence it would seem that they too did not believe that anything is by
chance. But there is a further circumstance that is surprising. Many things both come to be and are by chance
and spontaneity, and although know that each of them can be ascribed to some cause (as the old argument
said which denied chance), nevertheless they speak of some of these things as happening by chance and
others not. For this reason also they ought to have at least referred to the matter in some way or other.

Certainly the early physicists found no place for chance among the causes which they recognized-love, strife,
mind, fire, or the like. This is strange, whether they supposed that there is no such thing as chance or whether
they thought there is but omitted to mention it-and that too when they sometimes used it, as Empedocles
does when he says that the air is not always separated into the highest region, but 'as it may chance'. At any
rate he says in his cosmogony that 'it happened to run that way at that time, but it often ran otherwise.' He

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tells us also that most of the parts of animals came to be by chance.

There are some too who ascribe this heavenly sphere and all the worlds to spontaneity. They say that the
vortex arose spontaneously, i.e. the motion that separated and arranged in its present order all that exists. This
statement might well cause surprise. For they are asserting that chance is not responsible for the existence or
generation of animals and plants, nature or mind or something of the kind being the cause of them (for it is
not any chance thing that comes from a given seed but an olive from one kind and a man from another); and
yet at the same time they assert that the heavenly sphere and the divinest of visible things arose
spontaneously, having no such cause as is assigned to animals and plants. Yet if this is so, it is a fact which
deserves to be dwelt upon, and something might well have been said about it. For besides the other
absurdities of the statement, it is the more absurd that people should make it when they see nothing coming to
be spontaneously in the heavens, but much happening by chance among the things which as they say are not
due to chance; whereas we should have expected exactly the opposite.

Others there are who, indeed, believe that chance is a cause, but that it is inscrutable to human intelligence, as
being a divine thing and full of mystery.

Thus we must inquire what chance and spontaneity are, whether they are the same or different, and how they
fit into our division of causes.

First then we observe that some things always come to pass in the same way, and others for the most part. It
is clearly of neither of these that chance is said to be the cause, nor can the 'effect of chance' be identified
with any of the things that come to pass by necessity and always, or for the most part. But as there is a third
class of events besides these two-events which all say are 'by chance'-it is plain that there is such a thing as
chance and spontaneity; for we know that things of this kind are due to chance and that things due to chance
are of this kind.

But, secondly, some events are for the sake of something, others not. Again, some of the former class are in
accordance with deliberate intention, others not, but both are in the class of things which are for the sake of
something. Hence it is clear that even among the things which are outside the necessary and the normal, there
are some in connexion withwhich the phrase 'for the sake of something' is applicable. (Events that are for the
sake of something include whatever may be done as a result of thought or of nature.) Things of this kind,
then, when they come to pass incidental are said to be 'by chance'. For just as a thing is something either in
virtue of itself or incidentally, so may it be a cause. For instance, the housebuilding faculty is in virtue of
itself the cause of a house, whereas the pale or the musical is the incidental cause. That which is per se cause
of the effect is determinate, but the incidental cause is indeterminable, for the possible attributes of an
individual are innumerable. To resume then; when a thing of this kind comes to pass among events which are
for the sake of something, it is said to be spontaneous or by chance. (The distinction between the two must be
made later-for the present it is sufficient if it is plain that both are in the sphere of things done for the sake of
something.)

Example: A man is engaged in collecting subscriptions for a feast. He would have gone to such and such a
place for the purpose of getting the money, if he had known. He actually went there for another purpose and
it was only incidentally that he got his money by going there; and this was not due to the fact that he went
there as a rule or necessarily, nor is the end effected (getting the money) a cause present in himself-it belongs
to the class of things that are intentional and the result of intelligent deliberation. It is when these conditions
are satisfied that the man is said to have gone 'by chance'. If he had gone of deliberate purpose and for the
sake of this-if he always or normally went there when he was collecting payments-he would not be said to

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have gone 'by chance'.

It is clear then that chance is an incidental cause in the sphere of those actions for the sake of something
which involve purpose. Intelligent reflection, then, and chance are in the same sphere, for purpose implies
intelligent reflection.

It is necessary, no doubt, that the causes of what comes to pass by chance be indefinite; and that is why
chance is supposed to belong to the class of the indefinite and to be inscrutable to man, and why it might be
thought that, in a way, nothing occurs by chance. For all these statements are correct, because they are well
grounded. Things do, in a way, occur by chance, for they occur incidentally and chance is an incidental cause.
But strictly it is not the cause-without qualification-of anything; for instance, a housebuilder is the cause of a
house; incidentally, a fluteplayer may be so.

And the causes of the man's coming and getting the money (when he did not come for the sake of that) are
innumerable. He may have wished to see somebody or been following somebody or avoiding somebody, or
may have gone to see a spectacle. Thus to say that chance is a thing contrary to rule is correct. For 'rule'
applies to what is always true or true for the most part, whereas chance belongs to a third type of event.
Hence, to conclude, since causes of this kind are indefinite, chance too is indefinite. (Yet in some cases one
might raise the question whether any incidental fact might be the cause of the chance occurrence, e.g. of
health the fresh air or the sun's heat may be the cause, but having had one's hair cut cannot; for some
incidental causes are more relevant to the effect than others.)

Chance or fortune is called 'good' when the result is good, 'evil' when it is evil. The terms 'good fortune' and
'ill fortune' are used when either result is of considerable magnitude. Thus one who comes within an ace of
some great evil or great good is said to be fortunate or unfortunate. The mind affirms the essence of the
attribute, ignoring the hair's breadth of difference. Further, it is with reason that good fortune is regarded as
unstable; for chance is unstable, as none of the things which result from it can be invariable or normal.

Both are then, as I have said, incidental causes-both chance and spontaneity-in the sphere of things which
are capable of coming to pass not necessarily, nor normally, and with reference to such of these as might
come to pass for the sake of something.

They differ in that 'spontaneity' is the wider term. Every result of chance is from what is spontaneous, but not
everything that is from what is spontaneous is from chance.

Chance and what results from chance are appropriate to agents that are capable of good fortune and of moral
action generally. Therefore necessarily chance is in the sphere of moral actions. This is indicated by the fact
that good fortune is thought to be the same, or nearly the same, as happiness, and happiness to be a kind of
moral action, since it is well-doing. Hence what is not capable of moral action cannot do anything by chance.
Thus an inanimate thing or a lower animal or a child cannot do anything by chance, because it is incapable of
deliberate intention; nor can 'good fortune' or 'ill fortune' be ascribed to them, except metaphorically, as
Protarchus, for example, said that the stones of which altars are made are fortunate because they are held in
honour, while their fellows are trodden under foot. Even these things, however, can in a way be affected by
chance, when one who is dealing with them does something to them by chance, but not otherwise.

The spontaneous on the other hand is found both in the lower animals and in many inanimate objects. We
say, for example, that the horse came 'spontaneously', because, though his coming saved him, he did not
come for the sake of safety. Again, the tripod fell 'of itself, because, though when it fell it stood on its feet so

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PHYSICS

as to serve for a seat, it did not fall for the sake of that.

Hence it is clear that events which (1) belong to the general class of things that may come to pass for the sake
of something, (2) do not come to pass for the sake of what actually results, and (3) have an external cause,
may be described by the phrase 'from spontaneity'. These 'spontaneous' events are said to be 'from chance' if
they have the further characteristics of being the objects of deliberate intention and due to agents capable of
that mode of action. This is indicated by the phrase 'in vain', which is used when A which is for the sake of B,
does not result in B. For instance, taking a walk is for the sake of evacuation of the bowels; if this does not
follow after walking, we say that we have walked 'in vain' and that the walking was 'vain'. This implies that
what is naturally the means to an end is 'in vain', when it does not effect the end towards which it was the
natural means-for it would be absurd for a man to say that he had bathed in vain because the sun was not
eclipsed, since the one was not done with a view to the other. Thus the spontaneous is even according to its
derivation the case in which the thing itself happens in vain. The stone that struck the man did not fall for the
purpose of striking him; therefore it fell spontaneously, because it might have fallen by the action of an agent
and for the purpose of striking. The difference between spontaneity and what results by chance is greatest in
things that come to be by nature; for when anything comes to be contrary to nature, we do not say that it came
to be by chance, but by spontaneity. Yet strictly this too is different from the spontaneous proper; for the
cause of the latter is external, that of the former internal.

We have now explained what chance is and what spontaneity is, and in what they differ from each other.
Both belong to the mode of causation 'source of change', for either some natural or some intelligent agent is
always the cause; but in this sort of causation the number of possible causes is infinite.

Spontaneity and chance are causes of effects which though they might result from intelligence or nature, have
in fact been caused by something incidentally. Now since nothing which is incidental is prior to what is per
se, it is clear that no incidental cause can be prior to a cause per se. Spontaneity and chance, therefore, are
posterior to intelligence and nature. Hence, however true it may be that the heavens are due to spontaneity, it
will still be true that intelligence and nature will be prior causes of this All and of many things in it besides.

It is clear then that there are causes, and that the number of them is what we have stated. The number is the
same as that of the things comprehended under the question 'why'. The 'why' is referred ultimately either (1),
in things which do not involve motion, e.g. in mathematics, to the 'what' (to the definition of 'straight line' or
'commensurable', or (2) to what initiated a motion, e.g. 'why did they go to war?-because there had been a
raid'; or (3) we are inquiring 'for the sake of what?'-'that they may rule'; or (4), in the case of things that come
into being, we are looking for the matter. The causes, therefore, are these and so many in number.

Now, the causes being four, it is the business of the physicist to know about them all, and if he refers his
problems back to all of them, he will assign the 'why' in the way proper to his science-the matter, the form,
the mover, 'that for the sake of which'. The last three often coincide; for the 'what' and 'that for the sake of
which' are one, while the primary source of motion is the same in species as these (for man generates man),
and so too, in general, are all things which cause movement by being themselves moved; and such as are not
of this kind are no longer inside the province of physics, for they cause motion not by possessing motion or a
source of motion in themselves, but being themselves incapable of motion. Hence there are three branches of
study, one of things which are incapable of motion, the second of things in motion, but indestructible, the
third of destructible things.

The question 'why', then, is answered by reference to the matter, to the form, and to the primary moving
cause. For in respect of coming to be it is mostly in this last way that causes are investigated-'what comes to

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PHYSICS

be after what? what was the primary agent or patient?' and so at each step of the series.

Now the principles which cause motion in a physical way are two, of which one is not physical, as it has no
principle of motion in itself. Of this kind is whatever causes movement, not being itself moved, such as (1)
that which is completely unchangeable, the primary reality, and (2) the essence of that which is coming to be,
i.e. the form; for this is the end or 'that for the sake of which'. Hence since nature is for the sake of something,
we must know this cause also. We must explain the 'why' in all the senses of the term, namely, (1) that from
this that will necessarily result ('from this' either without qualification or in most cases); (2) that 'this must be
so if that is to be so' (as the conclusion presupposes the premisses); (3) that this was the essence of the thing;
and (4) because it is better thus (not without qualification, but with reference to the essential nature in each
case).

We must explain then (1) that Nature belongs to the class of causes which act for the sake of something; (2)
about the necessary and its place in physical problems, for all writers ascribe things to this cause, arguing that
since the hot and the cold, are of such and such a kind, therefore certain things necessarily are and come to
be-and if they mention any other cause (one his 'friendship and strife', another his 'mind'), it is only to touch
on it, and then good-bye to it.

A difficulty presents itself: why should not nature work, not for the sake of something, nor because it is better
so, but just as the sky rains, not in order to make the corn grow, but of necessity? What is drawn up must
cool, and what has been cooled must become water and descend, the result of this being that the corn grows.
Similarly if a man's crop is spoiled on the threshing-floor, the rain did not fall for the sake of this-in order
that the crop might be spoiled-but that result just followed. Why then should it not be the same with the parts
in nature, e.g. that our teeth should come up of necessity-the front teeth sharp, fitted for tearing, the molars
broad and useful for grinding down the food-since they did not arise for this end, but it was merely a
coincident result; and so with all other parts in which we suppose that there is purpose? Wherever then all the
parts came about just what they would have been if they had come be for an end, such things survived, being
organized spontaneously in a fitting way; whereas those which grew otherwise perished and continue to
perish, as Empedocles says his 'man-faced ox-progeny' did.

Such are the arguments (and others of the kind) which may cause difficulty on this point. Yet it is impossible
that this should be the true view. For teeth and all other natural things either invariably or normally come
about in a given way; but of not one of the results of chance or spontaneity is this true. We do not ascribe to
chance or mere coincidence the frequency of rain in winter, but frequent rain in summer we do; nor heat in
the dog-days, but only if we have it in winter. If then, it is agreed that things are either the result of
coincidence or for an end, and these cannot be the result of coincidence or spontaneity, it follows that they
must be for an end; and that such things are all due to nature even the champions of the theory which is
before us would agree. Therefore action for an end is present in things which come to be and are by nature.

Further, where a series has a completion, all the preceding steps are for the sake of that. Now surely as in
intelligent action, so in nature; and as in nature, so it is in each action, if nothing interferes. Now intelligent
action is for the sake of an end; therefore the nature of things also is so. Thus if a house, e.g. had been a thing
made by nature, it would have been made in the same way as it is now by art; and if things made by nature
were made also by art, they would come to be in the same way as by nature. Each step then in the series is for
the sake of the next; and generally art partly completes what nature cannot bring to a finish, and partly
imitates her. If, therefore, artificial products are for the sake of an end, so clearly also are natural products.
The relation of the later to the earlier terms of the series is the same in both. This is most obvious in the
animals other than man: they make things neither by art nor after inquiry or deliberation. Wherefore people

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PHYSICS

discuss whether it is by intelligence or by some other faculty that these creatures work,spiders, ants, and the
like. By gradual advance in this direction we come to see clearly that in plants too that is produced which is
conducive to the end-leaves, e.g. grow to provide shade for the fruit. If then it is both by nature and for an
end that the swallow makes its nest and the spider its web, and plants grow leaves for the sake of the fruit and
send their roots down (not up) for the sake of nourishment, it is plain that this kind of cause is operative in
things which come to be and are by nature. And since 'nature' means two things, the matter and the form, of
which the latter is the end, and since all the rest is for the sake of the end, the form must be the cause in the
sense of 'that for the sake of which'.

Now mistakes come to pass even in the operations of art: the grammarian makes a mistake in writing and the
doctor pours out the wrong dose. Hence clearly mistakes are possible in the operations of nature also. If then
in art there are cases in which what is rightly produced serves a purpose, and if where mistakes occur there
was a purpose in what was attempted, only it was not attained, so must it be also in natural products, and
monstrosities will be failures in the purposive effort. Thus in the original combinations the 'ox-progeny' if
they failed to reach a determinate end must have arisen through the corruption of some principle
corresponding to what is now the seed.

Further, seed must have come into being first, and not straightway the animals: the words 'whole-natured
first...' must have meant seed.

Again, in plants too we find the relation of means to end, though the degree of organization is less. Were
there then in plants also 'olive-headed vine-progeny', like the 'man-headed ox-progeny', or not? An absurd
suggestion; yet there must have been, if there were such things among animals.

Moreover, among the seeds anything must have come to be at random. But the person who asserts this
entirely does away with 'nature' and what exists 'by nature'. For those things are natural which, by a
continuous movement originated from an internal principle, arrive at some completion: the same completion
is not reached from every principle; nor any chance completion, but always the tendency in each is towards
the same end, if there is no impediment.

The end and the means towards it may come about by chance. We say, for instance, that a stranger has come
by chance, paid the ransom, and gone away, when he does so as if he had come for that purpose, though it
was not for that that he came. This is incidental, for chance is an incidental cause, as I remarked before. But
when an event takes place always or for the most part, it is not incidental or by chance. In natural products the
sequence is invariable, if there is no impediment.

It is absurd to suppose that purpose is not present because we do not observe the agent deliberating. Art does
not deliberate. If the ship-building art were in the wood, it would produce the same results by nature. If,
therefore, purpose is present in art, it is present also in nature. The best illustration is a doctor doctoring
himself: nature is like that.

It is plain then that nature is a cause, a cause that operates for a purpose.

As regards what is 'of necessity', we must ask whether the necessity is 'hypothetical', or 'simple' as well. The
current view places what is of necessity in the process of production, just as if one were to suppose that the
wall of a house necessarily comes to be because what is heavy is naturally carried downwards and what is
light to the top, wherefore the stones and foundations take the lowest place, with earth above because it is
lighter, and wood at the top of all as being the lightest. Whereas, though the wall does not come to be without

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PHYSICS

these, it is not due to these, except as its material cause: it comes to be for the sake of sheltering and guarding
certain things. Similarly in all other things which involve production for an end; the product cannot come to
be without things which have a necessary nature, but it is not due to these (except as its material); it comes to
be for an end. For instance, why is a saw such as it is? To effect so-and-so and for the sake of so-and-so.
This end, however, cannot be realized unless the saw is made of iron. It is, therefore, necessary for it to be of
iron, it we are to have a saw and perform the operation of sawing. What is necessary then, is necessary on a
hypothesis; it is not a result necessarily determined by antecedents. Necessity is in the matter, while 'that for
the sake of which' is in the definition.

Necessity in mathematics is in a way similar to necessity in things which come to be through the operation of
nature. Since a straight line is what it is, it is necessary that the angles of a triangle should equal two right
angles. But not conversely; though if the angles are not equal to two right angles, then the straight line is not
what it is either. But in things which come to be for an end, the reverse is true. If the end is to exist or does
exist, that also which precedes it will exist or does exist; otherwise just as there, if-the conclusion is not true,
the premiss will not be true, so here the end or 'that for the sake of which' will not exist. For this too is itself a
starting-point, but of the reasoning, not of the action; while in mathematics the starting-point is the
starting-point of the reasoning only, as there is no action. If then there is to be a house, such-and-such things
must be made or be there already or exist, or generally the matter relative to the end, bricks and stones if it is
a house. But the end is not due to these except as the matter, nor will it come to exist because of them. Yet if
they do not exist at all, neither will the house, or the saw-the former in the absence of stones, the latter in the
absence of iron-just as in the other case the premisses will not be true, if the angles of the triangle are not
equal to two right angles.

The necessary in nature, then, is plainly what we call by the name of matter, and the changes in it. Both
causes must be stated by the physicist, but especially the end; for that is the cause of the matter, not vice
versa; and the end is 'that for the sake of which', and the beginning starts from the definition or essence; as in
artificial products, since a house is of such-and-such a kind, certain things must necessarily come to be or be
there already, or since health is this, these things must necessarily come to be or be there already. Similarly if
man is this, then these; if these, then those. Perhaps the necessary is present also in the definition. For if one
defines the operation of sawing as being a certain kind of dividing, then this cannot come about unless the
saw has teeth of a certain kind; and these cannot be unless it is of iron. For in the definition too there are
some parts that are, as it were, its matter.

Book III

NATURE has been defined as a 'principle of motion and change', and it is the subject of our inquiry. We must
therefore see that we understand the meaning of 'motion'; for if it were unknown, the meaning of 'nature' too
would be unknown.

When we have determined the nature of motion, our next task will be to attack in the same way the terms
which are involved in it. Now motion is supposed to belong to the class of things which are continuous; and
the infinite presents itself first in the continuous-that is how it comes about that 'infinite' is often used in
definitions of the continuous ('what is infinitely divisible is continuous'). Besides these, place, void, and time
are thought to be necessary conditions of motion.

Clearly, then, for these reasons and also because the attributes mentioned are common to, and coextensive
with, all the objects of our science, we must first take each of them in hand and discuss it. For the
investigation of special attributes comes after that of the common attributes.

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PHYSICS

To begin then, as we said, with motion.

We may start by distinguishing (1) what exists in a state of fulfilment only, (2) what exists as potential, (3)
what exists as potential and also in fulfilment-one being a 'this', another 'so much', a third 'such, and
similarly in each of the other modes of the predication of being.

Further, the word 'relative' is used with reference to (1) excess and defect, (2) agent and patient and generally
what can move and what can be moved. For 'what can cause movement' is relative to 'what can be moved',
and vice versa.

Again, there is no such thing as motion over and above the things. It is always with respect to substance or to
quantity or to quality or to place that what changes changes. But it is impossible, as we assert, to find
anything common to these which is neither 'this' nor quantum nor quale nor any of the other predicates.
Hence neither will motion and change have reference to something over and above the things mentioned, for
there is nothing over and above them.

Now each of these belongs to all its subjects in either of two ways: namely (1) substance-the one is positive
form, the other privation; (2) in quality, white and black; (3) in quantity, complete and incomplete; (4) in
respect of locomotion, upwards and downwards or light and heavy. Hence there are as many types of motion
or change as there are meanings of the word 'is'.

We have now before us the distinctions in the various classes of being between what is full real and what is
potential.

Def. The fulfilment of what exists potentially, in so far as it exists potentially, is motion-namely, of what is
alterable qua alterable, alteration: of what can be increased and its opposite what can be decreased (there is no
common name), increase and decrease: of what can come to be and can pass away, coming to he and passing
away: of what can be carried along, locomotion.

Examples will elucidate this definition of motion. When the buildable, in so far as it is just that, is fully real,
it is being built, and this is building. Similarly, learning, doctoring, rolling, leaping, ripening, ageing.

The same thing, if it is of a certain kind, can be both potential and fully real, not indeed at the same time or
not in the same respect, but e.g. potentially hot and actually cold. Hence at once such things will act and be
acted on by one another in many ways: each of them will be capable at the same time of causing alteration
and of being altered. Hence, too, what effects motion as a physical agent can be moved: when a thing of this
kind causes motion, it is itself also moved. This, indeed, has led some people to suppose that every mover is
moved. But this question depends on another set of arguments, and the truth will be made clear later, is
possible for a thing to cause motion, though it is itself incapable of being moved.

It is the fulfilment of what is potential when it is already fully real and operates not as itself but as movable,
that is motion. What I mean by 'as' is this: Bronze is potentially a statue. But it is not the fulfilment of bronze
as bronze which is motion. For 'to be bronze' and 'to be a certain potentiality' are not the same.

If they were identical without qualification, i.e. in definition, the fulfilment of bronze as bronze would have
been motion. But they are not the same, as has been said. (This is obvious in contraries. 'To be capable of
health' and 'to be capable of illness' are not the same, for if they were there would be no difference between
being ill and being well. Yet the subject both of health and of sickness-whether it is humour or blood-is one
and the same.)

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PHYSICS

We can distinguish, then, between the two-just as, to give another example, 'colour' and visible' are
different-and clearly it is the fulfilment of what is potential as potential that is motion. So this, precisely, is
motion.

Further it is evident that motion is an attribute of a thing just when it is fully real in this way, and neither
before nor after. For each thing of this kind is capable of being at one time actual, at another not. Take for
instance the buildable as buildable. The actuality of the buildable as buildable is the process of building. For
the actuality of the buildable must be either this or the house. But when there is a house, the buildable is no
longer buildable. On the other hand, it is the buildable which is being built. The process then of being built
must be the kind of actuality required But building is a kind of motion, and the same account will apply to the
other kinds also.

The soundness of this definition is evident both when we consider the accounts of motion that the others have
given, and also from the difficulty of defining it otherwise.

One could not easily put motion and change in another genus-this is plain if we consider where some people
put it; they identify motion with or 'inequality' or 'not being'; but such things are not necessarily moved,
whether they are 'different' or 'unequal' or 'non-existent'; Nor is change either to or from these rather than to
or from their opposites.

The reason why they put motion into these genera is that it is thought to be something indefinite, and the
principles in the second column are indefinite because they are privative: none of them is either 'this' or 'such'
or comes under any of the other modes of predication. The reason in turn why motion is thought to be
indefinite is that it cannot be classed simply as a potentiality or as an actuality-a thing that is merely capable
of having a certain size is not undergoing change, nor yet a thing that is actually of a certain size, and motion
is thought to be a sort of actuality, but incomplete, the reason for this view being that the potential whose
actuality it is is incomplete. This is why it is hard to grasp what motion is. It is necessary to class it with
privation or with potentiality or with sheer actuality, yet none of these seems possible. There remains then the
suggested mode of definition, namely that it is a sort of actuality, or actuality of the kind described, hard to
grasp, but not incapable of existing.

The mover too is moved, as has been said-every mover, that is, which is capable of motion, and whose
immobility is rest-when a thing is subject to motion its immobility is rest. For to act on the movable as such
is just to move it. But this it does by contact, so that at the same time it is also acted on. Hence we can define
motion as the fulfilment of the movable qua movable, the cause of the attribute being contact with what can
move so that the mover is also acted on. The mover or agent will always be the vehicle of a form, either a
'this' or 'such', which, when it acts, will be the source and cause of the change, e.g. the full-formed man
begets man from what is potentially man.

The solution of the difficulty that is raised about the motion-whether it is in the movable-is plain. It is the
fulfilment of this potentiality, and by the action of that which has the power of causing motion; and the
actuality of that which has the power of causing motion is not other than the actuality of the movable, for it
must be the fulfilment of both. A thing is capable of causing motion because it can do this, it is a mover
because it actually does it. But it is on the movable that it is capable of acting. Hence there is a single
actuality of both alike, just as one to two and two to one are the same interval, and the steep ascent and the
steep descent are one-for these are one and the same, although they can be described in different ways. So it

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PHYSICS

is with the mover and the moved.

This view has a dialectical difficulty. Perhaps it is necessary that the actuality of the agent and that of the
patient should not be the same. The one is 'agency' and the other 'patiency'; and the outcome and completion
of the one is an 'action', that of the other a 'passion'. Since then they are both motions, we may ask: in what
are they, if they are different? Either (a) both are in what is acted on and moved, or (b) the agency is in the
agent and the patiency in the patient. (If we ought to call the latter also 'agency', the word would be used in
two senses.)

Now, in alternative (b), the motion will be in the mover, for the same statement will hold of 'mover' and
'moved'. Hence either every mover will be moved, or, though having motion, it will not be moved.

If on the other hand (a) both are in what is moved and acted on-both the agency and the patiency (e.g. both
teaching and learning, though they are two, in the learner), then, first, the actuality of each will not be present
in each, and, a second absurdity, a thing will have two motions at the same time. How will there be two
alterations of quality in one subject towards one definite quality? The thing is impossible: the actualization
will be one.

But (some one will say) it is contrary to reason to suppose that there should be one identical actualization of
two things which are different in kind. Yet there will be, if teaching and learning are the same, and agency
and patiency. To teach will be the same as to learn, and to act the same as to be acted on-the teacher will
necessarily be learning everything that he teaches, and the agent will be acted on. One may reply:

(1) It is not absurd that the actualization of one thing should be in another. Teaching is the activity of a person
who can teach, yet the operation is performed on some patient-it is not cut adrift from a subject, but is of A
onB.

(2) There is nothing to prevent two things having one and the same actualization, provided the actualizations
are not described in the same way, but are related as what can act to what is acting.

(3) Nor is it necessary that the teacher should learn, even if to act and to be acted on are one and the same,
provided they are not the same in definition (as 'raiment' and 'dress'), but are the same merely in the sense in
which the road from Thebes to Athens and the road from Athens to Thebes are the same, as has been
explained above. For it is not things which are in a way the same that have all their attributes the same, but
only such as have the same definition. But indeed it by no means follows from the fact that teaching is the
same as learning, that to learn is the same as to teach, any more than it follows from the fact that there is one
distance between two things which are at a distance from each other, that the two vectors AB and BA, are one
and the same. To generalize, teaching is not the same as learning, or agency as patiency, in the full sense,
though they belong to the same subject, the motion; for the 'actualization of X in Y' and the 'actualization of
Y through the action of X' differ in definition.

What then Motion is, has been stated both generally and particularly. It is not difficult to see how each of its
types will be defined-alteration is the fulfillment of the alterable qua alterable (or, more scientifically, the
fulfilment of what can act and what can be acted on, as such)-generally and again in each particular case,
building, healing, A similar definition will apply to each of the other kinds of motion.

The science of nature is concerned with spatial magnitudes and motion and time, and each of these at least is
necessarily infinite or finite, even if some things dealt with by the science are not, e.g. a quality or a point-it

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PHYSICS

is not necessary perhaps that such things should be put under either head. Hence it is incumbent on the person
who specializes in physics to discuss the infinite and to inquire whether there is such a thing or not, and, if
there is, what it is.

The appropriateness to the science of this problem is clearly indicated. All who have touched on this kind of
science in a way worth considering have formulated views about the infinite, and indeed, to a man, make it a
principle of things.

(1) Some, as the Pythagoreans and Plato, make the infinite a principle in the sense of a self-subsistent
substance, and not as a mere attribute of some other thing. Only the Pythagoreans place the infinite among
the objects of sense (they do not regard number as separable from these), and assert that what is outside the
heaven is infinite. Plato, on the other hand, holds that there is no body outside (the Forms are not outside
because they are nowhere),yet that the infinite is present not only in the objects of sense but in the Forms
also.

Further, the Pythagoreans identify the infinite with the even. For this, they say, when it is cut off and shut in
by the odd, provides things with the element of infinity. An indication of this is what happens with numbers.
If the gnomons are placed round the one, and without the one, in the one construction the figure that results is
always different, in the other it is always the same. But Plato has two infinites, the Great and the Small.

The physicists, on the other hand, all of them, always regard the infinite as an attribute of a substance which
is different from it and belongs to the class of the so-called elements-water or air or what is intermediate
between them. Those who make them limited in number never make them infinite in amount. But those who
make the elements infinite in number, as Anaxagoras and Democritus do, say that the infinite is continuous
by contact-compounded of the homogeneous parts according to the one, of the seed-mass of the atomic
shapes according to the other.

Further, Anaxagoras held that any part is a mixture in the same way as the All, on the ground of the observed
fact that anything comes out of anything. For it is probably for this reason that he maintains that once upon a
time all things were together. (This flesh and this bone were together, and so of any thing: therefore all
things: and at the same time too.) For there is a beginning of separation, not only for each thing, but for all.
Each thing that comes to be comes from a similar body, and there is a coming to be of all things, though not,
it is true, at the same time. Hence there must also be an origin of coming to be. One such source there is
which he calls Mind, and Mind begins its work of thinking from some starting-point. So necessarily all
things must have been together at a certain time, and must have begun to be moved at a certain time.

Democritus, for his part, asserts the contrary, namely that no element arises from another element.
Nevertheless for him the common body is a source of all things, differing from part to part in size and in
shape.

It is clear then from these considerations that the inquiry concerns the physicist. Nor is it without reason that
they all make it a principle or source. We cannot say that the infinite has no effect, and the only effectiveness
which we can ascribe to it is that of a principle. Everything is either a source or derived from a source. But
there cannot be a source of the infinite or limitless, for that would be a limit of it. Further, as it is a beginning,
it is both uncreatable and indestructible. For there must be a point at which what has come to be reaches
completion, and also a termination of all passing away. That is why, as we say, there is no principle of this,
but it is this which is held to be the principle of other things, and to encompass all and to steer all, as those
assert who do not recognize, alongside the infinite, other causes, such as Mind or Friendship. Further they
identify it with the Divine, for it is 'deathless and imperishable' as Anaximander says, with the majority of the
physicists.

PHYSICS

Belief in the existence of the infinite comes mainly from five considerations:

(1) From the nature of time-for it is infinite.

(2) From the division of magnitudes-for the mathematicians also use the notion of the infinite.

(3) If coming to be and passing away do not give out, it is only because that from which things come to be is
infinite.

(4) Because the limited always finds its limit in something, so that there must be no limit, if everything is
always limited by something different from itself.

(5) Most of all, a reason which is peculiarly appropriate and presents the difficulty that is felt by
everybody-not only number but also mathematical magnitudes and what is outside the heaven are supposed
to be infinite because they never give out in our thought.

The last fact (that what is outside is infinite) leads people to suppose that body also is infinite, and that there
is an infinite number of worlds. Why should there be body in one part of the void rather than in another?
Grant only that mass is anywhere and it follows that it must be everywhere. Also, if void and place are
infinite, there must be infinite body too, for in the case of eternal things what may be must be. But the
problem of the infinite is difficult: many contradictions result whether we suppose it to exist or not to exist. If
it exists, we have still to ask how it exists; as a substance or as the essential attribute of some entity? Or in
neither way, yet none the less is there something which is infinite or some things which are infinitely many?

The problem, however, which specially belongs to the physicist is to investigate whether there is a sensible
magnitude which is infinite.

We must begin by distinguishing the various senses in which the term 'infinite' is used.

(1) What is incapable of being gone through, because it is not in its nature to be gone through (the sense in
which the voice is 'invisible').

(2) What admits of being gone through, the process however having no termination, or what scarcely admits
of being gone through.

(3) What naturally admits of being gone through, but is not actually gone through or does not actually reach
an end.

Further, everything that is infinite may be so in respect of addition or division or both.

Now it is impossible that the infinite should be a thing which is itself infinite, separable from sensible objects.
If the infinite is neither a magnitude nor an aggregate, but is itself a substance and not an attribute, it will be
indivisible; for the divisible must be either a magnitude or an aggregate. But if indivisible, then not infinite,
except in the sense (1) in which the voice is 'invisible'. But this is not the sense in which it is used by those
who say that the infinite exists, nor that in which we are investigating it, namely as (2) 'that which cannot be
gone through'. But if the infinite exists as an attribute, it would not be, qua infinite an element in substances,
any more than the invisible would be an element of speech, though the voice is invisible.

PHYSICS

Further, how can the infinite be itself any thing, unless both number and magnitude, of which it is an essential
attribute, exist in that way? If they are not substances, a fortiori the infinite is not.

It is plain, too, that the infinite cannot be an actual thing and a substance and principle. For any part of it that
is taken will be infinite, if it has parts: for 'to be infinite' and 'the infinite' are the same, if it is a substance and
not predicated of a subject. Hence it will be either indivisible or divisible into infinites. But the same thing
cannot be many infinites. (Yet just as part of air is air, so a part of the infinite would be infinite, if it is
supposed to be a substance and principle.) Therefore the infinite must be without parts and indivisible. But
this cannot be true of what is infinite in full completion: for it must be a definite quantity.

Suppose then that infinity belongs to substance as an attribute. But, if so, it cannot, as we have said, be
described as a principle, but rather that of which it is an attribute-the air or the even number.

Thus the view of those who speak after the manner of the Pythagoreans is absurd. With the same breath they
treat the infinite as substance, and divide it into parts.

This discussion, however, involves the more general question whether the infinite can be present in
mathematical objects and things which are intelligible and do not have extension, as well as among sensible
objects. Our inquiry (as physicists) is limited to its special subject-matter, the objects of sense, and we have
to ask whether there is or is not among them a body which is infinite in the direction of increase.

We may begin with a dialectical argument and show as follows that there is no such thing. If 'bounded by a
surface' is the definition of body there cannot be an infinite body either intelligible or sensible. Nor can
number taken in abstraction be infinite, for number or that which has number is numerable. If then the
numerable can be numbered, it would also be possible to go through the infinite.

If, on the other hand, we investigate the question more in accordance with principles appropriate to physics,
we are led as follows to the same result.

The infinite body must be either (1) compound, or (2) simple; yet neither alternative is possible.

(1) Compound the infinite body will not be, if the elements are finite in number. For they must be more than
one, and the contraries must always balance, and no one of them can be infinite. If one of the bodies falls in
any degree short of the other in potency-suppose fire is finite in amount while air is infinite and a given
quantity of fire exceeds in power the same amount of air in any ratio provided it is numerically definite-the
infinite body will obviously prevail over and annihilate the finite body. On the other hand, it is impossible
that each should be infinite. 'Body' is what has extension in all directions and the infinite is what is
boundlessly extended, so that the infinite body would be extended in all directions ad infinitum.

Nor (2) can the infinite body be one and simple, whether it is, as some hold, a thing over and above the
elements (from which they generate the elements) or is not thus qualified.

(a) We must consider the former alternative; for there are some people who make this the infinite, and not air
or water, in order that the other elements may not be annihilated by the element which is infinite. They have
contrariety with each other-air is cold, water moist, fire hot; if one were infinite, the others by now would
have ceased to be. As it is, they say, the infinite is different from them and is their source.

It is impossible, however, that there should be such a body; not because it is infinite on that point a general
proof can be given which applies equally to all, air, water, or anything else-but simply because there is, as a
matter of fact, no such sensible body, alongside the so-called elements. Everything can be resolved into the
elements of which it is composed. Hence the body in question would have been present in our world here,

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alongside air and fire and earth and water: but nothing of the kind is observed.

(b) Nor can fire or any other of the elements be infinite. For generally, and apart from the question of how
any of them could be infinite, the All, even if it were limited, cannot either be or become one of them, as
Heraclitus says that at some time all things become fire. (The same argument applies also to the one which
the physicists suppose to exist alongside the elements: for everything changes from contrary to contrary, e.g.
from hot to cold).

The preceding consideration of the various cases serves to show us whether it is or is not possible that there
should be an infinite sensible body. The following arguments give a general demonstration that it is not
possible.

It is the nature of every kind of sensible body to be somewhere, and there is a place appropriate to each, the
same for the part and for the whole, e.g. for the whole earth and for a single clod, and for fire and for a spark.

Suppose (a) that the infinite sensible body is homogeneous. Then each part will be either immovable or
always being carried along. Yet neither is possible. For why downwards rather than upwards or in any other
direction? I mean, e.g, if you take a clod, where will it be moved or where will it be at rest? For ex hypothesi
the place of the body akin to it is infinite. Will it occupy the whole place, then? And how? What then will be
the nature of its rest and of its movement, or where will they be? It will either be at home everywhere-then it
will not be moved; or it will be moved everywhere-then it will not come to rest.

But if (b) the All has dissimilar parts, the proper places of the parts will be dissimilar also, and the body of
the All will have no unity except that of contact. Then, further, the parts will be either finite or infinite in
variety of kind, (i) Finite they cannot be, for if the All is to be infinite, some of them would have to be
infinite, while the others were not, e.g. fire or water will be infinite. But, as we have seen before, such an
element would destroy what is contrary to it. (This indeed is the reason why none of the physicists made fire
or earth the one infinite body, but either water or air or what is intermediate between them, because the abode
of each of the two was plainly determinate, while the others have an ambiguous place between up and down.)

But (ii) if the parts are infinite in number and simple, their proper places too will be infinite in number, and
the same will be true of the elements themselves. If that is impossible, and the places are finite, the whole too
must be finite; for the place and the body cannot but fit each other. Neither is the whole place larger than
what can be filled by the body (and then the body would no longer be infinite), nor is the body larger than the
place; for either there would be an empty space or a body whose nature it is to be nowhere.

Anaxagoras gives an absurd account of why the infinite is at rest. He says that the infinite itself is the cause
of its being fixed. This because it is in itself, since nothing else contains it-on the assumption that wherever
anything is, it is there by its own nature. But this is not true: a thing could be somewhere by compulsion, and
not where it is its nature to be.

Even if it is true as true can be that the whole is not moved (for what is fixed by itself and is in itself must be
immovable), yet we must explain why it is not its nature to be moved. It is not enough just to make this
statement and then decamp. Anything else might be in a state of rest, but there is no reason why it should not
be its nature to be moved. The earth is not carried along, and would not be carried along if it were infinite,
provided it is held together by the centre. But it would not be because there was no other region in which it
could be carried along that it would remain at the centre, but because this is its nature. Yet in this case also
we may say that it fixes itself. If then in the case of the earth, supposed to be infinite, it is at rest, not because
it is infinite, but because it has weight and what is heavy rests at the centre and the earth is at the centre,
similarly the infinite also would rest in itself, not because it is infinite and fixes itself, but owing to some
other cause.

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Another difficulty emerges at the same time. Any part of the infinite body ought to remain at rest. Just as the
infinite remains at rest in itself because it fixes itself, so too any part of it you may take will remain in itself.
The appropriate places of the whole and of the part are alike, e.g. of the whole earth and of a clod the
appropriate place is the lower region; of fire as a whole and of a spark, the upper region. If, therefore, to be in
itself is the place of the infinite, that also will be appropriate to the part. Therefore it will remain in itself.

In general, the view that there is an infinite body is plainly incompatible with the doctrine that there is
necessarily a proper place for each kind of body, if every sensible body has either weight or lightness, and if a
body has a natural locomotion towards the centre if it is heavy, and upwards if it is light. This would need to
be true of the infinite also. But neither character can belong to it: it cannot be either as a whole, nor can it be
half the one and half the other. For how should you divide it? or how can the infinite have the one part up and
the other down, or an extremity and a centre?

Further, every sensible body is in place, and the kinds or differences of place are up-down, before-behind,
right-left; and these distinctions hold not only in relation to us and by arbitrary agreement, but also in the
whole itself. But in the infinite body they cannot exist. In general, if it is impossible that there should be an
infinite place, and if every body is in place, there cannot be an infinite body.

Surely what is in a special place is in place, and what is in place is in a special place. Just, then, as the infinite
cannot be quantity-that would imply that it has a particular quantity, e,g, two or three cubits; quantity just
means these-so a thing's being in place means that it is somewhere, and that is either up or down or in some
other of the six differences of position: but each of these is a limit.

It is plain from these arguments that there is no body which is actually infinite.

But on the other hand to suppose that the infinite does not exist in any way leads obviously to many
impossible consequences: there will be a beginning and an end of time, a magnitude will not be divisible into
magnitudes, number will not be infinite. If, then, in view of the above considerations, neither alternative
seems possible, an arbiter must be called in; and clearly there is a sense in which the infinite exists and
another in which it does not.

We must keep in mind that the word 'is' means either what potentially is or what fully is. Further, a thing is
infinite either by addition or by division.

Now, as we have seen, magnitude is not actually infinite. But by division it is infinite. (There is no difficulty
in refuting the theory of indivisible lines.) The alternative then remains that the infinite has a potential
existence.

But the phrase 'potential existence' is ambiguous. When we speak of the potential existence of a statue we
mean that there will be an actual statue. It is not so with the infinite. There will not be an actual infinite. The
word 'is' has many senses, and we say that the infinite 'is' in the sense in which we say 'it is day' or 'it is the
games', because one thing after another is always coming into existence. For of these things too the
distinction between potential and actual existence holds. We say that there are Olympic games, both in the
sense that they may occur and that they are actually occurring.

The infinite exhibits itself in different ways-in time, in the generations of man, and in the division of
magnitudes. For generally the infinite has this mode of existence: one thing is always being taken after
another, and each thing that is taken is always finite, but always different. Again, 'being' has more than one

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sense, so that we must not regard the infinite as a 'this', such as a man or a horse, but must suppose it to exist
in the sense in which we speak of the day or the games as existing things whose being has not come to them
like that of a substance, but consists in a process of coming to be or passing away; definite if you like at each
stage, yet always different.

But when this takes place in spatial magnitudes, what is taken perists, while in the succession of time and of
men it takes place by the passing away of these in such a way that the source of supply never gives out.

In a way the infinite by addition is the same thing as the infinite by division. In a finite magnitude, the infinite
by addition comes about in a way inverse to that of the other. For in proportion as we see division going on,
in the same proportion we see addition being made to what is already marked off. For if we take a
determinate part of a finite magnitude and add another part determined by the same ratio (not taking in the
same amount of the original whole), and so on, we shall not traverse the given magnitude. But if we increase
the ratio of the part, so as always to take in the same amount, we shall traverse the magnitude, for every finite
magnitude is exhausted by means of any determinate quantity however small.

The infinite, then, exists in no other way, but in this way it does exist, potentially and by reduction. It exists
fully in the sense in which we say 'it is day' or 'it is the games'; and potentially as matter exists, not
independently as what is finite does.

By addition then, also, there is potentially an infinite, namely, what we have described as being in a sense the
same as the infinite in respect of division. For it will always be possible to take something ah extra. Yet the
sum of the parts taken will not exceed every determinate magnitude, just as in the direction of division every
determinate magnitude is surpassed in smallness and there will be a smaller part.

But in respect of addition there cannot be an infinite which even potentially exceeds every assignable
magnitude, unless it has the attribute of being actually infinite, as the physicists hold to be true of the body
which is outside the world, whose essential nature is air or something of the kind. But if there cannot be in
this way a sensible body which is infinite in the full sense, evidently there can no more be a body which is
potentially infinite in respect of addition, except as the inverse of the infinite by division, as we have said. It
is for this reason that Plato also made the infinites two in number, because it is supposed to be possible to
exceed all limits and to proceed ad infinitum in the direction both of increase and of reduction. Yet though he
makes the infinites two, he does not use them. For in the numbers the infinite in the direction of reduction is
not present, as the monad is the smallest; nor is the infinite in the direction of increase, for the parts number
only up to the decad.

The infinite turns out to be the contrary of what it is said to be. It is not what has nothing outside it that is
infinite, but what always has something outside it. This is indicated by the fact that rings also that have no
bezel are described as 'endless', because it is always possible to take a part which is outside a given part. The
description depends on a certain similarity, but it is not true in the full sense of the word. This condition alone
is not sufficient: it is necessary also that the next part which is taken should never be the same. In the circle,
the latter condition is not satisfied: it is only the adjacent part from which the new part is different.

Our definition then is as follows:

A quantity is infinite if it is such that we can always take a part outside what has been already taken. On the
other hand, what has nothing outside it is complete and whole. For thus we define the whole-that from which
nothing is wanting, as a whole man or a whole box. What is true of each particular is true of the whole as
such-the whole is that of which nothing is outside. On the other hand that from which something is absent
and outside, however small that may be, is not 'all'. 'Whole' and 'complete' are either quite identical or closely
akin. Nothing is complete (teleion) which has no end (telos); and the end is a limit.

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Hence Parmenides must be thought to have spoken better than Melissus. The latter says that the whole is
infinite, but the former describes it as limited, 'equally balanced from the middle'. For to connect the infinite
with the all and the whole is not like joining two pieces of string; for it is from this they get the dignity they
ascribe to the infinite-its containing all things and holding the all in itself-from its having a certain similarity
to the whole. It is in fact the matter of the completeness which belongs to size, and what is potentially a
whole, though not in the full sense. It is divisible both in the direction of reduction and of the inverse
addition. It is a whole and limited; not, however, in virtue of its own nature, but in virtue of what is other than
it. It does not contain, but, in so far as it is infinite, is contained. Consequently, also, it is unknowable, qua
infinite; for the matter has no form. (Hence it is plain that the infinite stands in the relation of part rather than
of whole. For the matter is part of the whole, as the bronze is of the bronze statue.) If it contains in the case of
sensible things, in the case of intelligible things the great and the small ought to contain them. But it is absurd
and impossible to suppose that the unknowable and indeterminate should contain and determine.

It is reasonable that there should not be held to be an infinite in respect of addition such as to surpass every
magnitude, but that there should be thought to be such an infinite in the direction of division. For the matter
and the infinite are contained inside what contains them, while it is the form which contains. It is natural too
to suppose that in number there is a limit in the direction of the minimum, and that in the other direction
every assigned number is surpassed. In magnitude, on the contrary, every assigned magnitude is surpassed in
the direction of smallness, while in the other direction there is no infinite magnitude. The reason is that what
is one is indivisible whatever it may be, e.g. a man is one man, not many. Number on the other hand is a
plurality of 'ones' and a certain quantity of them. Hence number must stop at the indivisible: for 'two' and
'three' are merely derivative terms, and so with each of the other numbers. But in the direction of largeness it
is always possible to think of a larger number: for the number of times a magnitude can be bisected is infinite.
Hence this infinite is potential, never actual: the number of parts that can be taken always surpasses any
assigned number. But this number is not separable from the process of bisection, and its infinity is not a
permanent actuality but consists in a process of coming to be, like time and the number of time.

With magnitudes the contrary holds. What is continuous is divided ad infinitum, but there is no infinite in the
direction of increase. For the size which it can potentially be, it can also actually be. Hence since no sensible
magnitude is infinite, it is impossible to exceed every assigned magnitude; for if it were possible there would
be something bigger than the heavens.

The infinite is not the same in magnitude and movement and time, in the sense of a single nature, but its
secondary sense depends on its primary sense, i.e. movement is called infinite in virtue of the magnitude
covered by the movement (or alteration or growth), and time because of the movement. (I use these terms for
the moment. Later I shall explain what each of them means, and also why every magnitude is divisible into
magnitudes.)

Our account does not rob the mathematicians of their science, by disproving the actual existence of the
infinite in the direction of increase, in the sense of the untraver sable. In point of fact they do not need the
infinite and do not use it. They postulate only that the finite straight line may be produced as far as they wish.
It is possible to have divided in the same ratio as the largest quantity another magnitude of any size you like.
Hence, for the purposes of proof, it will make no difference to them to have such an infinite instead, while its
existence will be in the sphere of real magnitudes.

In the fourfold scheme of causes, it is plain that the infinite is a cause in the sense of matter, and that its
essence is privation, the subject as such being what is continuous and sensible. All the other thinkers, too,
evidently treat the infinite as matter-that is why it is inconsistent in them to make it what contains, and not

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what is contained.

It remains to dispose of the arguments which are supposed to support the view that the infinite exists not only
potentially but as a separate thing. Some have no cogency; others can be met by fresh objections that are
valid.

(1) In order that coming to be should not fail, it is not necessary that there should be a sensible body which is
actually infinite. The passing away of one thing may be the coming to be of another, the All being limited.

(2) There is a difference between touching and being limited. The former is relative to something and is the
touching of something (for everything that touches touches something), and further is an attribute of some
one of the things which are limited. On the other hand, what is limited is not limited in relation to anything.
Again, contact is not necessarily possible between any two things taken at random.

(3) To rely on mere thinking is absurd, for then the excess or defect is not in the thing but in the thought. One
might think that one of us is bigger than he is and magnify him ad infinitum. But it does not follow that he is
bigger than the size we are, just because some one thinks he is, but only because he is the size he is. The
thought is an accident.

(a) Time indeed and movement are infinite, and also thinking, in the sense that each part that is taken passes
in succession out of existence.

(b) Magnitude is not infinite either in the way of reduction or of magnification in thought.

This concludes my account of the way in which the infinite exists, and of the way in which it does not exist,
and of what it is.

Book IV

THE physicist must have a knowledge of Place, too, as well as of the infinite-namely, whether there is such a
thing or not, and the manner of its existence and what it is-both because all suppose that things which exist
are somewhere (the non-existent is nowhere — where is the goat-stag or the sphinx?), and because 'motion'
in its most general and primary sense is change of place, which we call 'locomotion'.

The question, what is place? presents many difficulties. An examination of all the relevant facts seems to lead
to divergent conclusions. Moreover, we have inherited nothing from previous thinkers, whether in the way of
a statement of difficulties or of a solution.

The existence of place is held to be obvious from the fact of mutual replacement. Where water now is, there
in turn, when the water has gone out as from a vessel, air is present. When therefore another body occupies
this same place, the place is thought to be different from all the bodies which come to be in it and replace one
another. What now contains air formerly contained water, so that clearly the place or space into which and
out of which they passed was something different from both.

Further, the typical locomotions of the elementary natural bodies-namely, fire, earth, and the like-show not
only that place is something, but also that it exerts a certain influence. Each is carried to its own place, if it is

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not hindered, the one up, the other down. Now these are regions or kinds of place-up and down and the rest
of the six directions. Nor do such distinctions (up and down and right and left, hold only in relation to us. To
us they are not always the same but change with the direction in which we are turned: that is why the same
thing may be both right and left, up and down, before and behind. But in nature each is distinct, taken apart
by itself. It is not every chance direction which is 'up', but where fire and what is light are carried; similarly,
too, 'down' is not any chance direction but where what has weight and what is made of earth are carried-the
implication being that these places do not differ merely in relative position, but also as possessing distinct
potencies. This is made plain also by the objects studied by mathematics. Though they have no real place,
they nevertheless, in respect of their position relatively to us, have a right and left as attributes ascribed to
them only in consequence of their relative position, not having by nature these various characteristics. Again,
the theory that the void exists involves the existence of place: for one would define void as place bereft of
body.

These considerations then would lead us to suppose that place is something distinct from bodies, and that
every sensible body is in place. Hesiod too might be held to have given a correct account of it when he made
chaos first. At least he says:

'First of all things came chaos to being, then broad-breasted earth,' implying that things need to have space
first, because he thought, with most people, that everything is somewhere and in place. If this is its nature, the
potency of place must be a marvellous thing, and take precedence of all other things. For that without which
nothing else can exist, while it can exist without the others, must needs be first; for place does not pass out of
existence when the things in it are annihilated.

True, but even if we suppose its existence settled, the question of its nature presents difficulty-whether it is
some sort of 'bulk' of body or some entity other than that, for we must first determine its genus.

(1) Now it has three dimensions, length, breadth, depth, the dimensions by which all body also is bounded.
But the place cannot be body; for if it were there would be two bodies in the same place.

(2) Further, if body has a place and space, clearly so too have surface and the other limits of body; for the
same statement will apply to them: where the bounding planes of the water were, there in turn will be those of
the air. But when we come to a point we cannot make a distinction between it and its place. Hence if the
place of a point is not different from the point, no more will that of any of the others be different, and place
will not be something different from each of them.

(3) What in the world then are we to suppose place to be? If it has the sort of nature described, it cannot be an
element or composed of elements, whether these be corporeal or incorporeal: for while it has size, it has not
body. But the elements of sensible bodies are bodies, while nothing that has size results from a combination
of intelligible elements.

(4) Also we may ask: of what in things is space the cause? None of the four modes of causation can be
ascribed to it. It is neither in the sense of the matter of existents (for nothing is composed of it), nor as the
form and definition of things, nor as end, nor does it move existents.

(5) Further, too, if it is itself an existent, where will it be? Zeno's difficulty demands an explanation: for if
everything that exists has a place, place too will have a place, and so on ad infinitum.

(6) Again, just as every body is in place, so, too, every place has a body in it. What then shall we say about
growing things? It follows from these premisses that their place must grow with them, if their place is neither
less nor greater than they are.

PHYSICS

By asking these questions, then, we must raise the whole problem about place-not only as to what it is, but
even whether there is such a thing.

We may distinguish generally between predicating B of A because it (A) is itself, and because it is something
else; and particularly between place which is common and in which all bodies are, and the special place
occupied primarily by each. I mean, for instance, that you are now in the heavens because you are in the air
and it is in the heavens; and you are in the air because you are on the earth; and similarly on the earth because
you are in this place which contains no more than you.

Now if place is what primarily contains each body, it would be a limit, so that the place would be the form or
shape of each body by which the magnitude or the matter of the magnitude is defined: for this is the limit of
each body.

If, then, we look at the question in this way the place of a thing is its form. But, if we regard the place as the
extension of the magnitude, it is the matter. For this is different from the magnitude: it is what is contained
and defined by the form, as by a bounding plane. Matter or the indeterminate is of this nature; when the
boundary and attributes of a sphere are taken away, nothing but the matter is left.

This is why Plato in the Timaeus says that matter and space are the same; for the 'participant' and space are
identical. (It is true, indeed, that the account he gives there of the 'participant' is different from what he says
in his so-called 'unwritten teaching'. Nevertheless, he did identify place and space.) I mention Plato because,
while all hold place to be something, he alone tried to say what it is.

In view of these facts we should naturally expect to find difficulty in determining what place is, if indeed it is
one of these two things, matter or form. They demand a very close scrutiny, especially as it is not easy to
recognize them apart.

But it is at any rate not difficult to see that place cannot be either of them. The form and the matter are not
separate from the thing, whereas the place can be separated. As we pointed out, where air was, water in turn
comes to be, the one replacing the other; and similarly with other bodies. Hence the place of a thing is neither
a part nor a state of it, but is separable from it. For place is supposed to be something like a vessel-the vessel
being a transportable place. But the vessel is no part of the thing.

In so far then as it is separable from the thing, it is not the form: qua containing, it is different from the
matter.

Also it is held that what is anywhere is both itself something and that there is a different thing outside it.
(Plato of course, if we may digress, ought to tell us why the form and the numbers are not in place, if 'what
participates' is place-whether what participates is the Great and the Small or the matter, as he called it in
writing in the Timaeus.)

Further, how could a body be carried to its own place, if place was the matter or the form? It is impossible
that what has no reference to motion or the distinction of up and down can be place. So place must be looked
for among things which have these characteristics.

If the place is in the thing (it must be if it is either shape or matter) place will have a place: for both the form
and the indeterminate undergo change and motion along with the thing, and are not always in the same place,
but are where the thing is. Hence the place will have a place.

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Further, when water is produced from air, the place has been destroyed, for the resulting body is not in the
same place. What sort of destruction then is that?

This concludes my statement of the reasons why space must be something, and again of the difficulties that
may be raised about its essential nature.

The next step we must take is to see in how many senses one thing is said to be 'in' another.

(1) As the finger is 'in' the hand and generally the part 'in' the whole.

(2) As the whole is 'in' the parts: for there is no whole over and above the parts.

(3) As man is 'in' animal and generally species 'in' genus.

(4) As the genus is 'in' the species and generally the part of the specific form 'in' the definition of the specific
form.

(5) As health is 'in' the hot and the cold and generally the form 'in' the matter.

(6) As the affairs of Greece centre 'in' the king, and generally events centre 'in' their primary motive agent.

(7) As the existence of a thing centres 'in its good and generally 'in' its end, i.e. in 'that for the sake of which
it exists.

(8) In the strictest sense of all, as a thing is 'in' a vessel, and generally 'in' place.

One might raise the question whether a thing can be in itself, or whether nothing can be in itself-everything
being either nowhere or in something else.

The question is ambiguous; we may mean the thing qua itself or qua something else.

When there are parts of a whole-the one that in which a thing is, the other the thing which is in it-the whole
will be described as being in itself. For a thing is described in terms of its parts, as well as in terms of the
thing as a whole, e.g. a man is said to be white because the visible surface of him is white, or to be scientific
because his thinking faculty has been trained. The jar then will not be in itself and the wine will not be in
itself. But the jar of wine will: for the contents and the container are both parts of the same whole.

In this sense then, but not primarily, a thing can be in itself, namely, as 'white' is in body (for the visible
surface is in body), and science is in the mind.

It is from these, which are 'parts' (in the sense at least of being 'in' the man), that the man is called white, But
the jar and the wine in separation are not parts of a whole, though together they are. So when there are parts, a
thing will be in itself, as 'white' is in man because it is in body, and in body because it resides in the visible
surface. We cannot go further and say that it is in surface in virtue of something other than itself. (Yet it is not
in itself: though these are in a way the same thing,) they differ in essence, each having a special nature and
capacity, 'surface' and 'white'.

Thus if we look at the matter inductively we do not find anything to be 'in' itself in any of the senses that have
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been distinguished; and it can be seen by argument that it is impossible. For each of two things will have to
be both, e.g. the jar will have to be both vessel and wine, and the wine both wine and jar, if it is possible for a
thing to be in itself; so that, however true it might be that they were in each other, the jar will receive the wine
in virtue not of its being wine but of the wine's being wine, and the wine will be in the jar in virtue not of its
being a jar but of the jar's being a jar. Now that they are different in respect of their essence is evident; for
'that in which something is' and 'that which is in it' would be differently defined.

Nor is it possible for a thing to be in itself even incidentally: for two things would at the same time in the
same thing. The jar would be in itself-if a thing whose nature it is to receive can be in itself; and that which it
receives, namely (if wine) wine, will be in it.

Obviously then a thing cannot be in itself primarily.

Zeno's problem-that if Place is something it must be in something-is not difficult to solve. There is nothing
to prevent the first place from being 'in' something else-not indeed in that as 'in' place, but as health is 'in' the
hot as a positive determination of it or as the hot is 'in' body as an affection. So we escape the infinite regress.

Another thing is plain: since the vessel is no part of what is in it (what contains in the strict sense is different
from what is contained), place could not be either the matter or the form of the thing contained, but must
different-for the latter, both the matter and the shape, are parts of what is contained.

This then may serve as a critical statement of the difficulties involved.

What then after all is place? The answer to this question may be elucidated as follows.

Let us take for granted about it the various characteristics which are supposed correctly to belong to it
essentially. We assume then-

(1) Place is what contains that of which it is the place.

(2) Place is no part of the thing.

(3) The immediate place of a thing is neither less nor greater than the thing.

(4) Place can be left behind by the thing and is separable. In addition:

(5) All place admits of the distinction of up and down, and each of the bodies is naturally carried to its
appropriate place and rests there, and this makes the place either up or down.

Having laid these foundations, we must complete the theory. We ought to try to make our investigation such
as will render an account of place, and will not only solve the difficulties connected with it, but will also
show that the attributes supposed to belong to it do really belong to it, and further will make clear the cause
of the trouble and of the difficulties about it. Such is the most satisfactory kind of exposition.

First then we must understand that place would not have been thought of, if there had not been a special kind
of motion, namely that with respect to place. It is chiefly for this reason that we suppose the heaven also to be
in place, because it is in constant movement. Of this kind of change there are two species-locomotion on the
one hand and, on the other, increase and diminution. For these too involve variation of place: what was then

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in this place has now in turn changed to what is larger or smaller.

Again, when we say a thing is 'moved', the predicate either (1) belongs to it actually, in virtue of its own
nature, or (2) in virtue of something conjoined with it. In the latter case it may be either (a) something which
by its own nature is capable of being moved, e.g. the parts of the body or the nail in the ship, or (b) something
which is not in itself capable of being moved, but is always moved through its conjunction with something
else, as 'whiteness' or 'science'. These have changed their place only because the subjects to which they
belong do so.

We say that a thing is in the world, in the sense of in place, because it is in the air, and the air is in the world;
and when we say it is in the air, we do not mean it is in every part of the air, but that it is in the air because of
the outer surface of the air which surrounds it; for if all the air were its place, the place of a thing would not
be equal to the thing-which it is supposed to be, and which the primary place in which a thing is actually is.

When what surrounds, then, is not separate from the thing, but is in continuity with it, the thing is said to be
in what surrounds it, not in the sense of in place, but as a part in a whole. But when the thing is separate and
in contact, it is immediately 'in' the inner surface of the surrounding body, and this surface is neither a part of
what is in it nor yet greater than its extension, but equal to it; for the extremities of things which touch are
coincident.

Further, if one body is in continuity with another, it is not moved in that but with that. On the other hand it is
moved in that if it is separate. It makes no difference whether what contains is moved or not.

Again, when it is not separate it is described as a part in a whole, as the pupil in the eye or the hand in the
body: when it is separate, as the water in the cask or the wine in the jar. For the hand is moved with the body
and the water in the cask.

It will now be plain from these considerations what place is. There are just four things of which place must be
one-the shape, or the matter, or some sort of extension between the bounding surfaces of the containing
body, or this boundary itself if it contains no extension over and above the bulk of the body which comes to
be in it.

Three of these it obviously cannot be:

(1) The shape is supposed to be place because it surrounds, for the extremities of what contains and of what is
contained are coincident. Both the shape and the place, it is true, are boundaries. But not of the same thing:
the form is the boundary of the thing, the place is the boundary of the body which contains it.

(2) The extension between the extremities is thought to be something, because what is contained and separate
may often be changed while the container remains the same (as water may be poured from a vessel)-the
assumption being that the extension is something over and above the body displaced. But there is no such
extension. One of the bodies which change places and are naturally capable of being in contact with the
container falls in whichever it may chance to be.

If there were an extension which were such as to exist independently and be permanent, there would be an
infinity of places in the same thing. For when the water and the air change places, all the portions of the two
together will play the same part in the whole which was previously played by all the water in the vessel; at
the same time the place too will be undergoing change; so that there will be another place which is the place
of the place, and many places will be coincident. There is not a different place of the part, in which it is
moved, when the whole vessel changes its place: it is always the same: for it is in the (proximate) place where
they are that the air and the water (or the parts of the water) succeed each other, not in that place in which

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they come to be, which is part of the place which is the place of the whole world.

(3) The matter, too, might seem to be place, at least if we consider it in what is at rest and is thus separate but
in continuity. For just as in change of quality there is something which was formerly black and is now white,
or formerly soft and now hard-this is just why we say that the matter exists-so place, because it presents a
similar phenomenon, is thought to exist-only in the one case we say so because what was air is now water, in
the other because where air formerly was there a is now water. But the matter, as we said before, is neither
separable from the thing nor contains it, whereas place has both characteristics.

Well, then, if place is none of the three-neither the form nor the matter nor an extension which is always
there, different from, and over and above, the extension of the thing which is displaced-place necessarily is
the one of the four which is left, namely, the boundary of the containing body at which it is in contact with
the contained body. (By the contained body is meant what can be moved by way of locomotion.)

Place is thought to be something important and hard to grasp, both because the matter and the shape present
themselves along with it, and because the displacement of the body that is moved takes place in a stationary
container, for it seems possible that there should be an interval which is other than the bodies which are
moved. The air, too, which is thought to be incorporeal, contributes something to the belief: it is not only the
boundaries of the vessel which seem to be place, but also what is between them, regarded as empty. Just, in
fact, as the vessel is transportable place, so place is a non-portable vessel. So when what is within a thing
which is moved, is moved and changes its place, as a boat on a river, what contains plays the part of a vessel
rather than that of place. Place on the other hand is rather what is motionless: so it is rather the whole river
that is place, because as a whole it is motionless.

Hence we conclude that the innermost motionless boundary of what contains is place.

This explains why the middle of the heaven and the surface which faces us of the rotating system are held to
be 'up' and 'down' in the strict and fullest sense for all men: for the one is always at rest, while the inner side
of the rotating body remains always coincident with itself. Hence since the light is what is naturally carried
up, and the heavy what is carried down, the boundary which contains in the direction of the middle of the
universe, and the middle itself, are down, and that which contains in the direction of the outermost part of the
universe, and the outermost part itself, are up.

For this reason, too, place is thought to be a kind of surface, and as it were a vessel, i.e. a container of the
thing.

Further, place is coincident with the thing, for boundaries are coincident with the bounded.

If then a body has another body outside it and containing it, it is in place, and if not, not. That is why, even if
there were to be water which had not a container, the parts of it, on the one hand, will be moved (for one part
is contained in another), while, on the other hand, the whole will be moved in one sense, but not in another.
For as a whole it does not simultaneously change its place, though it will be moved in a circle: for this place
is the place of its parts. (Some things are moved, not up and down, but in a circle; others up and down, such
things namely as admit of condensation and rarefaction.)

As was explained, some things are potentially in place, others actually. So, when you have a homogeneous
substance which is continuous, the parts are potentially in place: when the parts are separated, but in contact,
like a heap, they are actually in place.

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Again, (1) some things are per se in place, namely every body which is movable either by way of locomotion
or by way of increase is per se somewhere, but the heaven, as has been said, is not anywhere as a whole, nor
in any place, if at least, as we must suppose, no body contains it. On the line on which it is moved, its parts
have place: for each is contiguous the next.

But (2) other things are in place indirectly, through something conjoined with them, as the soul and the
heaven. The latter is, in a way, in place, for all its parts are: for on the orb one part contains another. That is
why the upper part is moved in a circle, while the All is not anywhere. For what is somewhere is itself
something, and there must be alongside it some other thing wherein it is and which contains it. But alongside
the All or the Whole there is nothing outside the All, and for this reason all things are in the heaven; for the
heaven, we may say, is the All. Yet their place is not the same as the heaven. It is part of it, the innermost part
of it, which is in contact with the movable body; and for this reason the earth is in water, and this in the air,
and the air in the aether, and the aether in heaven, but we cannot go on and say that the heaven is in anything
else.

It is clear, too, from these considerations that all the problems which were raised about place will be solved
when it is explained in this way:

(1) There is no necessity that the place should grow with the body in it,

(2) Nor that a point should have a place,

(3) Nor that two bodies should be in the same place,

(4) Nor that place should be a corporeal interval: for what is between the boundaries of the place is any body
which may chance to be there, not an interval in body.

Further, (5) place is also somewhere, not in the sense of being in a place, but as the limit is in the limited; for
not everything that is is in place, but only movable body.

Also (6) it is reasonable that each kind of body should be carried to its own place. For a body which is next in
the series and in contact (not by compulsion) is akin, and bodies which are united do not affect each other,
while those which are in contact interact on each other.

Nor (7) is it without reason that each should remain naturally in its proper place. For this part has the same
relation to its place, as a separable part to its whole, as when one moves a part of water or air: so, too, air is
related to water, for the one is like matter, the other form-water is the matter of air, air as it were the actuality
of water, for water is potentially air, while air is potentially water, though in another way.

These distinctions will be drawn more carefully later. On the present occasion it was necessary to refer to
them: what has now been stated obscurely will then be made more clear. If the matter and the fulfilment are
the same thing (for water is both, the one potentially, the other completely), water will be related to air in a
way as part to whole. That is why these have contact: it is organic union when both become actually one.

This concludes my account of place-both of its existence and of its nature.

The investigation of similar questions about the void, also, must be held to belong to the physicist-namely
whether it exists or not, and how it exists or what it is-just as about place. The views taken of it involve

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arguments both for and against, in much the same sort of way. For those who hold that the void exists regard
it as a sort of place or vessel which is supposed to be 'full' when it holds the bulk which it is capable of
containing, 'void' when it is deprived of that-as if 'void' and 'full' and 'place' denoted the same thing, though
the essence of the three is different.

We must begin the inquiry by putting down the account given by those who say that it exists, then the
account of those who say that it does not exist, and third the current view on these questions.

Those who try to show that the void does not exist do not disprove what people really mean by it, but only
their erroneous way of speaking; this is true of Anaxagoras and of those who refute the existence of the void
in this way. They merely give an ingenious demonstration that air is something — by straining wine-skins
and showing the resistance of the air, and by cutting it off in clepsydras. But people really mean that there is
an empty interval in which there is no sensible body. They hold that everything which is in body is body and
say that what has nothing in it at all is void (so what is full of air is void). It is not then the existence of air
that needs to be proved, but the non-existence of an interval, different from the bodies, either separable or
actual-an interval which divides the whole body so as to break its continuity, as Democritus and Leucippus
hold, and many other physicists-or even perhaps as something which is outside the whole body, which
remains continuous.

These people, then, have not reached even the threshold of the problem, but rather those who say that the
void exists.

(1) They argue, for one thing, that change in place (i.e. locomotion and increase) would not be. For it is
maintained that motion would seem not to exist, if there were no void, since what is full cannot contain
anything more. If it could, and there were two bodies in the same place, it would also be true that any number
of bodies could be together; for it is impossible to draw a line of division beyond which the statement would
become untrue. If this were possible, it would follow also that the smallest body would contain the greatest;
for 'many a little makes a mickle': thus if many equal bodies can be together, so also can many unequal
bodies.

Melissus, indeed, infers from these considerations that the All is immovable; for if it were moved there must,
he says, be void, but void is not among the things that exist.

This argument, then, is one way in which they show that there is a void.

(2) They reason from the fact that some things are observed to contract and be compressed, as people say that
a cask will hold the wine which formerly filled it, along with the skins into which the wine has been
decanted, which implies that the compressed body contracts into the voids present in it.

Again (3) increase, too, is thought to take always by means of void, for nutriment is body, and it is impossible
for two bodies to be together. A proof of this they find also in what happens to ashes, which absorb as much
water as the empty vessel.

The Pythagoreans, too, (4) held that void exists and that it enters the heaven itself, which as it were inhales it,
from the infinite air. Further it is the void which distinguishes the natures of things, as if it were like what
separates and distinguishes the terms of a series. This holds primarily in the numbers, for the void
distinguishes their nature.

These, then, and so many, are the main grounds on which people have argued for and against the existence of
the void.

PHYSICS

As a step towards settling which view is true, we must determine the meaning of the name.

The void is thought to be place with nothing in it. The reason for this is that people take what exists to be
body, and hold that while every body is in place, void is place in which there is no body, so that where there
is no body, there must be void.

Every body, again, they suppose to be tangible; and of this nature is whatever has weight or lightness.

Hence, by a syllogism, what has nothing heavy or light in it, is void.

This result, then, as I have said, is reached by syllogism. It would be absurd to suppose that the point is void;
for the void must be place which has in it an interval in tangible body.

But at all events we observe then that in one way the void is described as what is not full of body perceptible
to touch; and what has heaviness and lightness is perceptible to touch. So we would raise the question: what
would they say of an interval that has colour or sound-is it void or not? Clearly they would reply that if it
could receive what is tangible it was void, and if not, not.

In another way void is that in which there is no 'this' or corporeal substance. So some say that the void is the
matter of the body (they identify the place, too, with this), and in this they speak incorrectly; for the matter is
not separable from the things, but they are inquiring about the void as about something separable.

Since we have determined the nature of place, and void must, if it exists, be place deprived of body, and we
have stated both in what sense place exists and in what sense it does not, it is plain that on this showing void
does not exist, either unseparated or separated; the void is meant to be, not body but rather an interval in
body. This is why the void is thought to be something, viz. because place is, and for the same reasons. For the
fact of motion in respect of place comes to the aid both of those who maintain that place is something over
and above the bodies that come to occupy it, and of those who maintain that the void is something. They state
that the void is the condition of movement in the sense of that in which movement takes place; and this would
be the kind of thing that some say place is.

But there is no necessity for there being a void if there is movement. It is not in the least needed as a
condition of movement in general, for a reason which, incidentally, escaped Melissus; viz. that the full can
suffer qualitative change.

But not even movement in respect of place involves a void; for bodies may simultaneously make room for
one another, though there is no interval separate and apart from the bodies that are in movement. And this is
plain even in the rotation of continuous things, as in that of liquids.

And things can also be compressed not into a void but because they squeeze out what is contained in them
(as, for instance, when water is compressed the air within it is squeezed out); and things can increase in size
not only by the entrance of something but also by qualitative change; e.g. if water were to be transformed into
air.

In general, both the argument about increase of size and that about water poured on to the ashes get in their
own way. For either not any and every part of the body is increased, or bodies may be increased otherwise
than by the addition of body, or there may be two bodies in the same place (in which case they are claiming
to solve a quite general difficulty, but are not proving the existence of void), or the whole body must be void,

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if it is increased in every part and is increased by means of void. The same argument applies to the ashes.
It is evident, then, that it is easy to refute the arguments by which they prove the existence of the void.

Let us explain again that there is no void existing separately, as some maintain. If each of the simple bodies
has a natural locomotion, e.g. fire upward and earth downward and towards the middle of the universe, it is
clear that it cannot be the void that is the condition of locomotion. What, then, will the void be the condition
of? It is thought to be the condition of movement in respect of place, and it is not the condition of this.

Again, if void is a sort of place deprived of body, when there is a void where will a body placed in it move
to? It certainly cannot move into the whole of the void. The same argument applies as against those who
think that place is something separate, into which things are carried; viz. how will what is placed in it move,
or rest? Much the same argument will apply to the void as to the 'up' and 'down' in place, as is natural enough
since those who maintain the existence of the void make it a place.

And in what way will things be present either in place-or in the void? For the expected result does not take
place when a body is placed as a whole in a place conceived of as separate and permanent; for a part of it,
unless it be placed apart, will not be in a place but in the whole. Further, if separate place does not exist,
neither will void.

If people say that the void must exist, as being necessary if there is to be movement, what rather turns out to
be the case, if one the matter, is the opposite, that not a single thing can be moved if there is a void; for as
with those who for a like reason say the earth is at rest, so, too, in the void things must be at rest; for there is
no place to which things can move more or less than to another; since the void in so far as it is void admits no
difference.

The second reason is this: all movement is either compulsory or according to nature, and if there is
compulsory movement there must also be natural (for compulsory movement is contrary to nature, and
movement contrary to nature is posterior to that according to nature, so that if each of the natural bodies has
not a natural movement, none of the other movements can exist); but how can there be natural movement if
there is no difference throughout the void or the infinite? For in so far as it is infinite, there will be no up or
down or middle, and in so far as it is a void, up differs no whit from down; for as there is no difference in
what is nothing, there is none in the void (for the void seems to be a non-existent and a privation of being),
but natural locomotion seems to be differentiated, so that the things that exist by nature must be
differentiated. Either, then, nothing has a natural locomotion, or else there is no void.

Further, in point of fact things that are thrown move though that which gave them their impulse is not
touching them, either by reason of mutual replacement, as some maintain, or because the air that has been
pushed pushes them with a movement quicker than the natural locomotion of the projectile wherewith it
moves to its proper place. But in a void none of these things can take place, nor can anything be moved save
as that which is carried is moved.

Further, no one could say why a thing once set in motion should stop anywhere; for why should it stop here
rather than here? So that a thing will either be at rest or must be moved ad infinitum, unless something more
powerful get in its way.

Further, things are now thought to move into the void because it yields; but in a void this quality is present
equally everywhere, so that things should move in all directions.

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Further, the truth of what we assert is plain from the following considerations. We see the same weight or
body moving faster than another for two reasons, either because there is a difference in what it moves
through, as between water, air, and earth, or because, other things being equal, the moving body differs from
the other owing to excess of weight or of lightness.

Now the medium causes a difference because it impedes the moving thing, most of all if it is moving in the
opposite direction, but in a secondary degree even if it is at rest; and especially a medium that is not easily
divided, i.e. a medium that is somewhat dense. A, then, will move through B in time G, and through D, which
is thinner, in time E (if the length of B is egual to D), in proportion to the density of the hindering body. For
let B be water and D air; then by so much as air is thinner and more incorporeal than water, A will move
through D faster than through B. Let the speed have the same ratio to the speed, then, that air has to water.
Then if air is twice as thin, the body will traverse B in twice the time that it does D, and the time G will be
twice the time E. And always, by so much as the medium is more incorporeal and less resistant and more
easily divided, the faster will be the movement.

Now there is no ratio in which the void is exceeded by body, as there is no ratio of to a number. For if 4
exceeds 3 by 1, and 2 by more than 1, and 1 by still more than it exceeds 2, still there is no ratio by which it
exceeds 0; for that which exceeds must be divisible into the excess + that which is exceeded, so that will be
what it exceeds by + 0. For this reason, too, a line does not exceed a point unless it is composed of points!
Similarly the void can bear no ratio to the full, and therefore neither can movement through the one to
movement through the other, but if a thing moves through the thickest medium such and such a distance in
such and such a time, it moves through the void with a speed beyond any ratio. For let Z be void, equal in
magnitude to B and to D. Then if A is to traverse and move through it in a certain time, H, a time less than E,
however, the void will bear this ratio to the full. But in a time equal to H, A will traverse the part O of A. And
it will surely also traverse in that time any substance Z which exceeds air in thickness in the ratio which the
time E bears to the time H. For if the body Z be as much thinner than D as E exceeds H, A, if it moves
through Z, will traverse it in a time inverse to the speed of the movement, i.e. in a time equal to H. If, then,
there is no body in Z, A will traverse Z still more quickly. But we supposed that its traverse of Z when Z was
void occupied the time H. So that it will traverse Z in an equal time whether Z be full or void. But this is
impossible. It is plain, then, that if there is a time in which it will move through any part of the void, this
impossible result will follow: it will be found to traverse a certain distance, whether this be full or void, in an
equal time; for there will be some body which is in the same ratio to the other body as the time is to the time.

To sum the matter up, the cause of this result is obvious, viz. that between any two movements there is a ratio
(for they occupy time, and there is a ratio between any two times, so long as both are finite), but there is no
ratio of void to full.

These are the consequences that result from a difference in the media; the following depend upon an excess
of one moving body over another. We see that bodies which have a greater impulse either of weight or of
lightness, if they are alike in other respects, move faster over an equal space, and in the ratio which their
magnitudes bear to each other. Therefore they will also move through the void with this ratio of speed. But
that is impossible; for why should one move faster? (In moving through plena it must be so; for the greater
divides them faster by its force. For a moving thing cleaves the medium either by its shape, or by the impulse
which the body that is carried along or is projected possesses.) Therefore all will possess equal velocity. But
this is impossible.

It is evident from what has been said, then, that, if there is a void, a result follows which is the very opposite
of the reason for which those who believe in a void set it up. They think that if movement in respect of place
is to exist, the void cannot exist, separated all by itself; but this is the same as to say that place is a separate
cavity; and this has already been stated to be impossible.

PHYSICS

But even if we consider it on its own merits the so-called vacuum will be found to be really vacuous. For as,
if one puts a cube in water, an amount of water equal to the cube will be displaced; so too in air; but the effect
is imperceptible to sense. And indeed always in the case of any body that can be displaced, must, if it is not
compressed, be displaced in the direction in which it is its nature to be displaced-always either down, if its
locomotion is downwards as in the case of earth, or up, if it is fire, or in both directions-whatever be the
nature of the inserted body. Now in the void this is impossible; for it is not body; the void must have
penetrated the cube to a distance equal to that which this portion of void formerly occupied in the void, just as
if the water or air had not been displaced by the wooden cube, but had penetrated right through it.

But the cube also has a magnitude equal to that occupied by the void; a magnitude which, if it is also hot or
cold, or heavy or light, is none the less different in essence from all its attributes, even if it is not separable
from them; I mean the volume of the wooden cube. So that even if it were separated from everything else and
were neither heavy nor light, it will occupy an equal amount of void, and fill the same place, as the part of
place or of the void equal to itself. How then will the body of the cube differ from the void or place that is
equal to it? And if there can be two such things, why cannot there be any number coinciding?

This, then, is one absurd and impossible implication of the theory. It is also evident that the cube will have
this same volume even if it is displaced, which is an attribute possessed by all other bodies also. Therefore if
this differs in no respect from its place, why need we assume a place for bodies over and above the volume of
each, if their volume be conceived of as free from attributes? It contributes nothing to the situation if there is
an equal interval attached to it as well. [Further it ought to be clear by the study of moving things what sort of
thing void is. But in fact it is found nowhere in the world. For air is something, though it does not seem to be
so-nor, for that matter, would water, if fishes were made of iron; for the discrimination of the tangible is by
touch.]

It is clear, then, from these considerations that there is no separate void.

There are some who think that the existence of rarity and density shows that there is a void. If rarity and
density do not exist, they say, neither can things contract and be compressed. But if this were not to take
place, either there would be no movement at all, or the universe would bulge, as Xuthus said, or air and water
must always change into equal amounts (e.g. if air has been made out of a cupful of water, at the same time
out of an equal amount of air a cupful of water must have been made), or void must necessarily exist; for
compression and expansion cannot take place otherwise.

Now, if they mean by the rare that which has many voids existing separately, it is plain that if void cannot
exist separate any more than a place can exist with an extension all to itself, neither can the rare exist in this
sense. But if they mean that there is void, not separately existent, but still present in the rare, this is less
impossible, yet, first, the void turns out not to be a condition of all movement, but only of movement upwards
(for the rare is light, which is the reason why they say fire is rare); second, the void turns out to be a condition
of movement not as that in which it takes place, but in that the void carries things up as skins by being carried
up themselves carry up what is continuous with them. Yet how can void have a local movement or a place?
For thus that into which void moves is till then void of a void.

Again, how will they explain, in the case of what is heavy, its movement downwards? And it is plain that if
the rarer and more void a thing is the quicker it will move upwards, if it were completely void it would move
with a maximum speed! But perhaps even this is impossible, that it should move at all; the same reason
which showed that in the void all things are incapable of moving shows that the void cannot move, viz. the
fact that the speeds are incomparable.

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Since we deny that a void exists, but for the rest the problem has been truly stated, that either there will be no
movement, if there is not to be condensation and rarefaction, or the universe will bulge, or a transformation of
water into air will always be balanced by an equal transformation of air into water (for it is clear that the air
produced from water is bulkier than the water): it is necessary therefore, if compression does not exist, either
that the next portion will be pushed outwards and make the outermost part bulge, or that somewhere else
there must be an equal amount of water produced out of air, so that the entire bulk of the whole may be equal,
or that nothing moves. For when anything is displaced this will always happen, unless it comes round in a
circle; but locomotion is not always circular, but sometimes in a straight line.

These then are the reasons for which they might say that there is a void; our statement is based on the
assumption that there is a single matter for contraries, hot and cold and the other natural contrarieties, and
that what exists actually is produced from a potential existent, and that matter is not separable from the
contraries but its being is different, and that a single matter may serve for colour and heat and cold.

The same matter also serves for both a large and a small body. This is evident; for when air is produced from
water, the same matter has become something different, not by acquiring an addition to it, but has become
actually what it was potentially, and, again, water is produced from air in the same way, the change being
sometimes from smallness to greatness, and sometimes from greatness to smallness. Similarly, therefore, if
air which is large in extent comes to have a smaller volume, or becomes greater from being smaller, it is the
matter which is potentially both that comes to be each of the two.

For as the same matter becomes hot from being cold, and cold from being hot, because it was potentially
both, so too from hot it can become more hot, though nothing in the matter has become hot that was not hot
when the thing was less hot; just as, if the arc or curve of a greater circle becomes that of a smaller, whether it
remains the same or becomes a different curve, convexity has not come to exist in anything that was not
convex but straight (for differences of degree do not depend on an intermission of the quality); nor can we get
any portion of a flame, in which both heat and whiteness are not present. So too, then, is the earlier heat
related to the later. So that the greatness and smallness, also, of the sensible volume are extended, not by the
matter's acquiring anything new, but because the matter is potentially matter for both states; so that the same
thing is dense and rare, and the two qualities have one matter.

The dense is heavy, and the rare is light. [Again, as the arc of a circle when contracted into a smaller space
does not acquire a new part which is convex, but what was there has been contracted; and as any part of fire
that one takes will be hot; so, too, it is all a question of contraction and expansion of the same matter.] There
are two types in each case, both in the dense and in the rare; for both the heavy and the hard are thought to be
dense, and contrariwise both the light and the soft are rare; and weight and hardness fail to coincide in the
case of lead and iron.

From what has been said it is evident, then, that void does not exist either separate (either absolutely separate
or as a separate element in the rare) or potentially, unless one is willing to call the condition of movement
void, whatever it may be. At that rate the matter of the heavy and the light, qua matter of them, would be the
void; for the dense and the rare are productive of locomotion in virtue of this contrariety, and in virtue of their
hardness and softness productive of passivity and impassivity, i.e. not of locomotion but rather of qualitative
change.

So much, then, for the discussion of the void, and of the sense in which it exists and the sense in which it
does not exist.

PHYSICS

Next for discussion after the subjects mentioned is Time. The best plan will be to begin by working out the
difficulties connected with it, making use of the current arguments. First, does it belong to the class of things
that exist or to that of things that do not exist? Then secondly, what is its nature? To start, then: the following
considerations would make one suspect that it either does not exist at all or barely, and in an obscure way.
One part of it has been and is not, while the other is going to be and is not yet. Yet time-both infinite time
and any time you like to take-is made up of these. One would naturally suppose that what is made up of
things which do not exist could have no share in reality.

Further, if a divisible thing is to exist, it is necessary that, when it exists, all or some of its parts must exist.
But of time some parts have been, while others have to be, and no part of it is though it is divisible. For what
is 'now' is not a part: a part is a measure of the whole, which must be made up of parts. Time, on the other
hand, is not held to be made up of 'nows'.

Again, the 'now' which seems to bound the past and the future-does it always remain one and the same or is
it always other and other? It is hard to say.

(1) If it is always different and different, and if none of the parts in time which are other and other are
simultaneous (unless the one contains and the other is contained, as the shorter time is by the longer), and if
the 'now' which is not, but formerly was, must have ceased-to-be at some time, the 'nows' too cannot be
simultaneous with one another, but the prior 'now' must always have ceased-to-be. But the prior 'now' cannot
have ceased-to-be in itself (since it then existed); yet it cannot have ceased-to-be in another 'now'. For we
may lay it down that one 'now' cannot be next to another, any more than point to point. If then it did not
cease-to-be in the next 'now' but in another, it would exist simultaneously with the innumerable 'nows'
between the two-which is impossible.

Yes, but (2) neither is it possible for the 'now' to remain always the same. No determinate divisible thing has
a single termination, whether it is continuously extended in one or in more than one dimension: but the 'now'
is a termination, and it is possible to cut off a determinate time. Further, if coincidence in time (i.e. being
neither prior nor posterior) means to be 'in one and the same "now"', then, if both what is before and what is
after are in this same 'now', things which happened ten thousand years ago would be simultaneous with what
has happened to-day, and nothing would be before or after anything else.

This may serve as a statement of the difficulties about the attributes of time.

As to what time is or what is its nature, the traditional accounts give us as little light as the preliminary
problems which we have worked through.

Some assert that it is (1) the movement of the whole, others that it is (2) the sphere itself.

(1) Yet part, too, of the revolution is a time, but it certainly is not a revolution: for what is taken is part of a
revolution, not a revolution. Besides, if there were more heavens than one, the movement of any of them
equally would be time, so that there would be many times at the same time.

(2) Those who said that time is the sphere of the whole thought so, no doubt, on the ground that all things are
in time and all things are in the sphere of the whole. The view is too naive for it to be worth while to consider
the impossibilities implied in it.

But as time is most usually supposed to be (3) motion and a kind of change, we must consider this view.
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PHYSICS

Now (a) the change or movement of each thing is only in the thing which changes or where the thing itself
which moves or changes may chance to be. But time is present equally everywhere and with all things.

Again, (b) change is always faster or slower, whereas time is not: for 'fast' and 'slow' are defined by
time-'fast' is what moves much in a short time, 'slow' what moves little in a long time; but time is not defined
by time, by being either a certain amount or a certain kind of it.

Clearly then it is not movement. (We need not distinguish at present between 'movement' and 'change'.)

But neither does time exist without change; for when the state of our own minds does not change at all, or we
have not noticed its changing, we do not realize that time has elapsed, any more than those who are fabled to
sleep among the heroes in Sardinia do when they are awakened; for they connect the earlier 'now' with the
later and make them one, cutting out the interval because of their failure to notice it. So, just as, if the 'now'
were not different but one and the same, there would not have been time, so too when its difference escapes
our notice the interval does not seem to be time. If, then, the non-realization of the existence of time happens
to us when we do not distinguish any change, but the soul seems to stay in one indivisible state, and when we
perceive and distinguish we say time has elapsed, evidently time is not independent of movement and change.
It is evident, then, that time is neither movement nor independent of movement.

We must take this as our starting-point and try to discover-since we wish to know what time is-what exactly
it has to do with movement.

Now we perceive movement and time together: for even when it is dark and we are not being affected
through the body, if any movement takes place in the mind we at once suppose that some time also has
elapsed; and not only that but also, when some time is thought to have passed, some movement also along
with it seems to have taken place. Hence time is either movement or something that belongs to movement.
Since then it is not movement, it must be the other.

But what is moved is moved from something to something, and all magnitude is continuous. Therefore the
movement goes with the magnitude. Because the magnitude is continuous, the movement too must be
continuous, and if the movement, then the time; for the time that has passed is always thought to be in
proportion to the movement.

The distinction of 'before' and 'after' holds primarily, then, in place; and there in virtue of relative position.
Since then 'before' and 'after' hold in magnitude, they must hold also in movement, these corresponding to
those. But also in time the distinction of 'before' and 'after' must hold, for time and movement always
correspond with each other. The 'before' and 'after' in motion is identical in substratum with motion yet
differs from it in definition, and is not identical with motion.

But we apprehend time only when we have marked motion, marking it by 'before' and 'after'; and it is only
when we have perceived 'before' and 'after' in motion that we say that time has elapsed. Now we mark them
by judging that A and B are different, and that some third thing is intermediate to them. When we think of the
extremes as different from the middle and the mind pronounces that the 'nows' are two, one before and one
after, it is then that we say that there is time, and this that we say is time. For what is bounded by the 'now' is
thought to be time-we may assume this.

When, therefore, we perceive the 'now' one, and neither as before and after in a motion nor as an identity but
in relation to a 'before' and an 'after', no time is thought to have elapsed, because there has been no motion

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either. On the other hand, when we do perceive a 'before' and an 'after', then we say that there is time. For
time is just this-number of motion in respect of 'before' and 'after'.

Hence time is not movement, but only movement in so far as it admits of enumeration. A proof of this: we
discriminate the more or the less by number, but more or less movement by time. Time then is a kind of
number. (Number, we must note, is used in two senses-both of what is counted or the countable and also of
that with which we count. Time obviously is what is counted, not that with which we count: there are
different kinds of thing.) Just as motion is a perpetual succession, so also is time. But every simultaneous
time is self-identical; for the 'now' as a subject is an identity, but it accepts different attributes. The 'now'
measures time, in so far as time involves the 'before and after'.

The 'now' in one sense is the same, in another it is not the same. In so far as it is in succession, it is different
(which is just what its being was supposed to mean), but its substratum is an identity: for motion, as was said,
goes with magnitude, and time, as we maintain, with motion. Similarly, then, there corresponds to the point
the body which is carried along, and by which we are aware of the motion and of the 'before and after'
involved in it. This is an identical substratum (whether a point or a stone or something else of the kind), but it
has different attributes as the sophists assume that Coriscus' being in the Lyceum is a different thing from
Coriscus' being in the market-place. And the body which is carried along is different, in so far as it is at one
time here and at another there. But the 'now' corresponds to the body that is carried along, as time
corresponds to the motion. For it is by means of the body that is carried along that we become aware of the
'before and after' the motion, and if we regard these as countable we get the 'now'. Hence in these also the
'now' as substratum remains the same (for it is what is before and after in movement), but what is predicated
of it is different; for it is in so far as the 'before and after' is numerable that we get the 'now'. This is what is
most knowable: for, similarly, motion is known because of that which is moved, locomotion because of that
which is carried, what is carried is a real thing, the movement is not. Thus what is called 'now' in one sense is
always the same; in another it is not the same: for this is true also of what is carried.

Clearly, too, if there were no time, there would be no 'now', and vice versa, just as the moving body and its
locomotion involve each other mutually, so too do the number of the moving body and the number of its
locomotion. For the number of the locomotion is time, while the 'now' corresponds to the moving body, and
is like the unit of number.

Time, then, also is both made continuous by the 'now' and divided at it. For here too there is a correspondence
with the locomotion and the moving body. For the motion or locomotion is made one by the thing which is
moved, because it is one-not because it is one in its own nature (for there might be pauses in the movement
of such a thing)-but because it is one in definition: for this determines the movement as 'before' and 'after'.
Here, too there is a correspondence with the point; for the point also both connects and terminates the
length-it is the beginning of one and the end of another. But when you take it in this way, using the one point
as two, a pause is necessary, if the same point is to be the beginning and the end. The 'now' on the other hand,
since the body carried is moving, is always different.

Hence time is not number in the sense in which there is 'number' of the same point because it is beginning
and end, but rather as the extremities of a line form a number, and not as the parts of the line do so, both for
the reason given (for we can use the middle point as two, so that on that analogy time might stand still), and
further because obviously the 'now' is no part of time nor the section any part of the movement, any more
than the points are parts of the line-for it is two lines that are parts of one line.

In so far then as the 'now' is a boundary, it is not time, but an attribute of it; in so far as it numbers, it is
number; for boundaries belong only to that which they bound, but number (e.g. ten) is the number of these
horses, and belongs also elsewhere.

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It is clear, then, that time is 'number of movement in respect of the before and after', and is continuous since it
is an attribute of what is continuous.

The smallest number, in the strict sense of the word 'number', is two. But of number as concrete, sometimes
there is a minimum, sometimes not: e.g. of a 'line', the smallest in respect of multiplicity is two (or, if you
like, one), but in respect of size there is no minimum; for every line is divided ad infinitum. Hence it is so
with time. In respect of number the minimum is one (or two); in point of extent there is no minimum.

It is clear, too, that time is not described as fast or slow, but as many or few and as long or short. For as
continuous it is long or short and as a number many or few, but it is not fast or slow-any more than any
number with which we number is fast or slow.

Further, there is the same time everywhere at once, but not the same time before and after, for while the
present change is one, the change which has happened and that which will happen are different. Time is not
number with which we count, but the number of things which are counted, and this according as it occurs
before or after is always different, for the 'nows' are different. And the number of a hundred horses and a
hundred men is the same, but the things numbered are different-the horses from the men. Further, as a
movement can be one and the same again and again, so too can time, e.g. a year or a spring or an autumn.

Not only do we measure the movement by the time, but also the time by the movement, because they define
each other. The time marks the movement, since it is its number, and the movement the time. We describe the
time as much or little, measuring it by the movement, just as we know the number by what is numbered, e.g.
the number of the horses by one horse as the unit. For we know how many horses there are by the use of the
number; and again by using the one horse as unit we know the number of the horses itself. So it is with the
time and the movement; for we measure the movement by the time and vice versa. It is natural that this
should happen; for the movement goes with the distance and the time with the movement, because they are
quanta and continuous and divisible. The movement has these attributes because the distance is of this nature,
and the time has them because of the movement. And we measure both the distance by the movement and the
movement by the distance; for we say that the road is long, if the journey is long, and that this is long, if the
road is long-the time, too, if the movement, and the movement, if the time.

Time is a measure of motion and of being moved, and it measures the motion by determining a motion which
will measure exactly the whole motion, as the cubit does the length by determining an amount which will
measure out the whole. Further 'to be in time' means for movement, that both it and its essence are measured
by time (for simultaneously it measures both the movement and its essence, and this is what being in time
means for it, that its essence should be measured).

Clearly then 'to be in time' has the same meaning for other things also, namely, that their being should be
measured by time. 'To be in time' is one of two things: (1) to exist when time exists, (2) as we say of some
things that they are 'in number'. The latter means either what is a part or mode of number-in general,
something which belongs to number-or that things have a number.

Now, since time is number, the 'now' and the 'before' and the like are in time, just as 'unit' and 'odd' and 'even'
are in number, i.e. in the sense that the one set belongs to number, the other to time. But things are in time as
they are in number. If this is so, they are contained by time as things in place are contained by place.

Plainly, too, to be in time does not mean to co-exist with time, any more than to be in motion or in place
means to co-exist with motion or place. For if 'to be in something' is to mean this, then all things will be in

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anything, and the heaven will be in a grain; for when the grain is, then also is the heaven. But this is a merely
incidental conjunction, whereas the other is necessarily involved: that which is in time necessarily involves
that there is time when it is, and that which is in motion that there is motion when it is.

Since what is 'in time' is so in the same sense as what is in number is so, a time greater than everything in
time can be found. So it is necessary that all the things in time should be contained by time, just like other
things also which are 'in anything', e.g. the things 'in place' by place.

The Complete Works of Aristotle - Part 4