De Anima

Cognition is in our eyes a thing of beauty and worth¹, and this is true of one cognition more than another, either because it is exact or because it relates to more important and remarkable objects. On both these grounds we may with good reason claim a high place for the enquiry concerning the soul. It would seem, too, that an acquaintance with the subject contributes greatly to the whole domain of truth and, more particularly, to the study of nature, the soul being virtually the principle of all animal life. Our aim is to discover and ascertain the nature and: essence of soul and, in the next place, all the accidents belonging to it; of which some are thought to be attributes peculiar to the soul itself, while others, it is held, belong to the animal also, but owe their existence to the soul. But everywhere and in every way it is extremely difficult to arrive at any trustworthy conclusion on the subject. It is the same here as in many other enquiries. What we have to investigate is the essential nature of things and the What. It might therefore be thought that there is a single procedure applicable to all the objects whose essential nature we wish to discover, as demonstration is applicable to the properties which go along with them: in that case we should have to enquire what this procedure is. If, however, there is no single procedure common to all sciences for defining the What, our task becomes still more difficult, as it will then be necessary to settle in each particular case the method to be pursued. Further, even if it be evident that it consists in demonstration of some sort or division or some other procedure, there

is still room for much perplexity and error, when we ask from what premisses our enquiry should start, for there are different premisses for different sciences; for the science of numbers, for example, and plane geometry.

The first thing necessary is no doubt to determine under which of the summa genera soul comes and what it is; I mean, whether it is a particular thing, i.e. substance, or is quality or is quantity, or falls under any other of the categories already determined. We must further ask whether it is amongst things potentially existent or is rather a sort of actuality, the distinction being all-important. Again, we must consider whether it is divisible or indivisible; whether, again, all and every soul is homogeneous or not; and, if not, whether the difference between the various souls is a difference of species or a difference of genus: for at present discussions and investigations about soul would appear to be restricted to the human soul. We must take care not to overlook the question whether there is a single definition of soul answering to a single definition of animal; or whether there is a different definition for each separate soul, as for horse and dog, man and god: animal, as the universal, being regarded either as non-existent or, if existent, as logically posterior. This is a question which might equally be raised in regard to any other common predicate. Further, on the assumption that there are not several souls, but merely several different parts in the same soul, it is a question whether we should begin by investigating soul as a whole or its several parts. And here again it is difficult to determine which of these parts are really distinct from one another and whether the several parts, or their functions, should be investigated first. Thus, e.g. should the process of thinking come first or the mind that thinks, the process of sensation or the sensitive faculty? And so everywhere else. But, if the functions should come first, again will arise the question whether we should first investigate the correlative objects. Shall we take, eg., the sensible object before the faculty of sense and the intelligible object before the intellect ?

It would seem that not only is the knowledge of a thing's essential nature useful for discovering the causes of its attributes, as, ¢.g., in mathematics the knowledge of what

' is meant by the terms straight or curved, line or surface, aids us in discovering to how many right angles the angles of a triangle are equal: but also, conversely, a knowledge of the attributes is a considerable aid to the knowledge of what a thing is.

For when we are able to give an account of all, or at any rate most, of the attributes as they are presented to us, then we shall be in a position to define most exactly the essential nature of the thing. In fact, the starting point of every demonstration is a definition of what something is. Hence the definitions which lead to no information about attributes and do not facilitate even conjecture respecting them have clearly been framed for dialectic and are void of content, one and all.

A further difficulty arises as to whether all attributes of the soul are also shared by that which contains the soul or whether any of them are peculiar to the soul itself: a question which it is indispensable, and yet by no means easy, to decide. It would appear that in most cases soul neither acts nor is acted upon apart from the body: as, e.g., in anger, confidence, desire and sensation in general. Thought, if anything, would seem to be peculiar to the soul. Yet, if thought is a sort of imagination, or not independent of imagination, it will follow that even thought cannot be independent of the body. If, then, there be any of the functions or affections of the soul peculiar to it, it will be possible for the soul to be separated from the body: if, on the other hand, there is nothing of the sort peculiar to it, the soul will not be capable of separate existence. As with the straight line, so with it. The line, qua straight, has many properties; for instance, it touches the brazen sphere at a point; but it by no means follows that it will so touch it if separated. In fact it is inseparable, since it is always conjoined with body of some sort. So, too, the attributes of the soul appear to be all conjoined with body: such attributes, viz., as anger, mildness, fear, pity, courage; also joy, love and hate; all of which are attended by some particular affection of the body. This indeed is shown by the fact that sometimes violent and palpable incentives occur without producing in us exasperation or fear, while at other times we are moved by slight and scarcely perceptible causes, when the blood is up and the bodily condition that of anger. Still more is this evident from the fact that sometimes even without the occurrence of anything terrible men exhibit all the symptoms of terror. If this be so, the attributes are evidently forms or notions realised in matter.

Hence they must be defined accordingly: anger, for instance, as a certain movement in a body of a given kind, or some part or faculty of it, produced by such and such a cause and for such and such an end. These facts at once bring the investigation of soul, whether in its entirety or in the particular aspect described, within the province of the natural philosopher. But every such attribute would be differently defined by the physicist and the dialectician or philosopher. Anger, for instance, would be defined by the dialectician as desire for retaliation or the like, by the physicist as a ferment of the blood or heat² which is about the heart: the one of them gives the matter, the other the form or notion. For the notion is the form of the thing, but this notion, if it is to be, must be realised in matter of a particular kind; just as in the case of a house. The notion or definition of a house would be as follows: a shelter to protect us from harm by wind or rain or scorching heat; while another will describe it as stones, bricks and timber; and again another as the form realised in these materials and subserving given ends. Which then of these is the true physicist? Is it he who confines himself to the matter, while ignoring the form? Or he who treats of the form exclusively? I answer, it is rather he who in his definition takes account of both. What then of each of the other two? Or shall we rather say that there is no one who deals with properties which are not separable nor yet treated as separable, but the physicist deals with all the active properties or passive affections belonging to body of a given sort and the corresponding matter? All attributes not regarded as so belonging he leaves to someone else: who in certain cases is an expert, a carpenter, for instance, or a physician. The attributes which, though inseparable, are not regarded as properties of body of a given sort, but are reached by abstraction, fall within the province of the mathematician: while attributes which are regarded as having separate existence fall to the first philosopher or metaphysician. But to return to the point of digression. We were saying that the attributes of the soul are as such,—I mean, as anger and fear, inseparable from the physical matter of the animals to which they belong, and not, like line and surface, separable in thought.

In our enquiry concerning soul it is necessary to state the problems which must be solved as we proceed, and at the same time to collect the views of our predecessors who had anything to say on the subject, in order that we may adopt what is right in their conclusions and guard against their mistakes. Our enquiry will begin by presenting what are commonly held to be in a special degree the natural attributes of soul. Now there are two points especially wherein that which is animate is held to differ from the inanimate, namely, motion and the act of sensation: and these are approximately the two characteristics of soul handed down to us by our predecessors. There are some who maintain that soul is preeminently and primarily the cause of movement. But they imagined that that which is not itself in motion cannot move anything else, and thus they regarded the soul as a thing which is in motion. Hence Democritus affirms the soul to be a sort of fire or heat. For the"shapes" or atoms are infinite and those which are spherical he declares to be fire and soul: they may be compared with the so-called motes in the air, which are seen in the sunbeams that enter through our windows. The aggregate of such seeds, he tells us, forms the constituent elements of the whole of nature (and herein he agrees with Leucippus), while those of them which are spherical form the soul, because such figures most easily find their way through everything and, beings themselves in motion, set other things in motion. The atomists assume that it is the soul which imparts motion to animals. It is for this reason that they make life depend upon respiration. For, when the surrounding air presses upon bodies and tends to extrude those atomic shapes which, because they are never at rest themselves, impart motion to animals, then they are reinforced from outside by the entry of other like atoms in respiration, which in fact, by helping to check compression and solidification, prevent the escape of the atoms already contained in the animals; and life, so they hold, continues so long as there is strength to do this. The doctrine of the Pythagoreans seems also to contain the same thought. Some of them identified soul with the motes in the air, others with that which sets these motes

in motion: and as to these motes it has been stated that they are seen to be in incessant motion, even though there be a perfect calm. The view of others who describe the soul as that which moves itself tends in the same direction. For it would seem that all these thinkers regard motion as the most distinctive characteristic of the soul. Everything else, they think, is moved by the soul, but the soul is moved by itself: and this because they never see anything cause motion without itself being in motion. Similarly the soul is said to be the moving principle by Anaxagoras and all others who have held that mind sets the universe in motion; but not altogether in the same sense as by Democritus. The latter, indeed, absolutely identified soul and mind, holding that the presentation to the senses is the truth: hence, he observed, Homer had well sung of Hector in his swoon that he lay "with other thoughts." Democritus, then, does not use the term mind to denote a faculty conversant with truth, but regards mind as identical with soul. Anaxagoras, however, is less exact in his use of the terms. In many places he speaks of mind as the cause of goodness and order, but elsewhere he identifies it with the soul: as where he attributes it to all animals, both great and small, high and low. As a matter of fact, however, mind in the sense of intelligence would not seem to be present in all animals alike, nor even in all men.

Those, then, who have directed their attention to the motion of the animate being, conceived the soul as that which is cognitive, most capable of causing motion: while those who laid stress on its knowledge and perception of all that exists identified the soul with the ultimate principles, whether they recognised a plurality of these or only one. Thus Empedocles compounded soul out of all the elements, while at the same time regarding each one of them as a soul. His words are "With earth we see earth, with water water, with air bright air, but ravaging fire by fire, love by love, and strife by

gruesome strife." In the same manner Plato in the Timaeus constructs the soul out of the elements. Like, he there maintains, is known by like, and the things we know are composed of the ultimate principles. In like manner it was explained in the lectures on philosophy, that the self-animal or universe is made up of the idea of One, and of the idea-numbers Two, or primary length, Three, primary breadth, and Four, primary depth, and similarly with all the rest of the ideas. And again this has been put in another way as follows: reason is the One, knowledge is the Two, because it proceeds by a single road to one conclusion, opinion is the number of a surface, Three, and sensation the number of a solid, Four. In fact, according to them the numbers, though they are the ideas themselves, or the ultimate principles, are nevertheless derived from elements. And things are judged, some by reason, others by knowledge, others again by opinion and others by sensation: while these idea-numbers are forms of things. And since the soul was held to be thus cognitive as well as capable of causing motion, some thinkers have combined the two and defined the soul as a self-moving number.

But there are differences of opinion as to the nature and number of the ultimate principles, especially between those who make the principles corporeal and those who make them incorporeal; and again between both of these and others who combine the two and take their principles from both. But, further, they differ also as to their ro number: some assuming a single principle, some a plurality. And, when they come to give an account of the soul, they do so in strict accordance with their several views. For they have assumed, not unnaturally, that the soul is that primary cause which in its own nature is capable of producing motion. And this is why some identified soul with fire, this being the element which is made up of the finest particles and is most nearly incorporeal, while further it is preeminently an element which both moves and sets other things in motion. Democritus has expressed more neatly the reason for each of these facts. Soul he regards as identical with mind, and this he makes to consist of the primary indivisible bodies and considers it to be a cause of motion from the fineness of its particles and their shape. Now the shape which is most susceptible of

motion is the spherical; and of atoms of this shape mind, like fire, consists. Anaxagoras, while apparently understanding by mind something different from soul, as we remarked above, really treats both as a single nature, except that it is preeminently mind which he takes as his first principle; he says at any rate that mind alone of things that exist is simple, unmixed, pure. But he refers both knowledge and motion to the same principle, when he says that mind sets the universe in motion. Thales, too, apparently, judging from the anecdotes related of him, conceived soul as a cause of motion, if it be true that he affirmed the loadstone to possess soul, because it attracts iron. Diogenes, however, as also some others, identified soul with air. Air, they thought, is made up of the finest particles and is the first principle: and this explains the fact that the soul knows and is a cause of motion, knowing by virtue of being the primary element from which all else is derived, and causing motion by the extreme fineness of its parts. Heraclitus takes soul for his first principle, as he identifies it with the vapour from which he derives all other things, and further says that it is the least corporeal of things and in ceaseless flux; and that it is by something in motion that what is in motion is known; for he, like most philosophers, conceived all that exists to be in motion. Alcmaeon, too, seems to have had a similar conception. or soul, he maintains, is immortal because it is like the beings which are immortal; and it has this attribute in virtue of being ever in motion: for he attributes continuous and unending motion to everything which is divine, moon, sun, stars and the whole heaven. Among cruder thinkers there have been some, like Hippon, who have even asserted the soul to be water. The reason for this view seems to have been the fact that in all animals the seed is moist: in fact, Hippon refutes those who make the soul to be blood by pointing out that the seed is not blood, and that this seed is the rudimentary soul. Others, again, like Critias, maintain the soul to be blood, holding that it is sentience which is most distinctive of soul and that this is due to the nature of blood. Thus each of the four elements except earth has found its supporter. Earth, however,

has not been put forward by anyone, except by those who have explained the soul to be derived from, or identical with, all the elements.

Thus practically all define the soul by three characteristics, motion, perception and incorporeality; and each of these characteristics is referred to the ultimate principles. Hence all who define soul by its capacity for knowledge either make it an element or derive it from the elements, being on this point, with one exception, in general agreement. Like, they tell us, is known by like; and therefore, since the soul knows all things, they say it consists of all the ultimate principles. Thus those thinkers who admit only one cause and one element, as fire or air, assume the soul also to be one element; while those who admit a plurality of principles assume plurality also in the soul. Anaxagoras alone says that mind cannot be acted upon and has nothing in common with any other thing. How, if such be its nature, it will know anything and how its knowledge is to be explained, he has omitted to state; nor do his utterances afford a clue. All those who introduce pairs of opposites among their principles make the soul also to consist of opposites; while those who take one or other of the two opposites, either hot or cold or something else of the sort, reduce the soul also to one or other of these elements. Hence, too, they etymologise according to their theories; some identify soul with heat, deriving ζῆν from ζεῖν, and contend that this identity accounts for the word for life; others say that what is cold is called soul from the respiratory process and consequent"cooling down," deriving ψυχή from ψύχειν. Such, then, are the views regarding soul which have come down to us and the grounds on which they are held.

We have to consider in the first place the subject of motion. For, unless I am mistaken, the definition of soul as the self-moving, or as that which is capable of self-motion, misrepresents its essential nature: nay, more; it is quite impossible for soul to have the attribute of motion at all. To begin with, it has been already stated that a thing may cause motion without necessarily being moved itself. A thing is always moved in one of two ways; that is, either indirectly,

through something else, or directly, of and through itself. We say things are moved through something else when they are in something else that is moved: as, for instance, sailors on board a ship: for they do not move in the same sense as the ship, for the ship moves of itself, they because they are in something else which is moved. This is evident if we consider the members of the body: for the motion proper to the feet and so to men also is walking, but it is not attributable to our sailors in the case supposed. There being thus two senses in which the term "to be moved" is used, we are now enquiring whether it is of and through itself that the soul is moved and partakes of motion.

Of motion there are four species, change of place or locomotion, change of quality or alteration, diminution and augmentation. It is, then, with one or more or all of these species that the soul will move. If it is not indirectly or per accidens that it moves, motion will be a natural attribute of soul; and, if this be so, it will also have position in space, since all the aforesaid species of motion are in space. But, if it be the essential nature of soul to move itself, motion will not be an accidental attribute of soul, as it is of whiteness or the length of three cubits; for these are also moved, but per accidens, viz. by the motion of the body to which these attributes belong. This, too, is why these attributes have no place belonging to them; but the soul will have a place, if indeed motion is its natural attribute.

Further, if it moves naturally, then it will also move under constraint; and, if under constraint, then also naturally. So likewise with rest. For, as it remains at rest naturally in any state into which it moves naturally, so similarly it remains at rest by constraint in any state into which it moves by constraint. But what is meant by constrained motions or states of rest of the soul it is not easy to explain, even though we give free play to fancy. Again, if its motion tends upward, it will be fire; if downward, earth; these being the motions proper to these natural bodies. And the same argument applies to directions of motion which are intermediate.

Again, since it appears that the soul sets the body in motion, it may reasonably be supposed to impart to it the motions which it has itself: and, if so, then conversely it is true to say that the motion which the soul has itself is the motion which the body

has. Now the motion of the body is motion in space: therefore the motion of the soul is also motion in space, whether the whole soul so move, or only the parts, the whole remaining at rest. But, if this is admissible, the soul might also conceivably quit the body and re-enter; and this would involve the consequence that dead animals may rise again.

To return now to motion per accidens, soul might certainly thus be moved by something external as well:—for the animal might be thrust by force. But a thing which has self-motion as part of its essential nature cannot be moved from without except incidentally; any more than that which is good in itself can be means to an end, or that which is good for its own sake can be so for the sake of something else. But, supposing the soul to be moved at all, one would say that sensible things would be the most likely to move it.

Again, even if soul does move itself, this is equivalent to saying that it is moved; and, all motion being defined as displacement of the thing moved, it will follow that the soul will be displaced from its own essential nature, if it be true that its self-movement is not an accident, but that motion belongs to the essence of soul in and of itself. Some say that the soul in fact moves the body, in which it is, in the same way in which it moves itself. So, for example, Democritus; and herein he resembled Philippus, the comic poet, who tells us that Daedalus endowed the wooden Aphrodite with motion, simply by pouring in quicksilver: this is very similar to what Democritus says. For according to him the spherical atoms, which from their nature can never remain still, being moved, tend to draw the whole body after them and thus set it in motion. But do these same atoms, we shall ask in our turn, produce rest, as well as motion? How this should be, it is difficult, if not impossible, to say. And, speaking generally, it is not in this way that the soul would seem to move the animal, but by means of purpose of some sort, that is, thought.

In the same way the Platonic Timaeus explains on physical grounds that the soul sets the body in motion, for by its own motion it sets the body also in motion, because it is closely interwoven with it. For when it had been made out of

the elements and divided in harmonical ratios in order that it might have a native perception of proportion and that the universe might move in harmonic revolutions, he, the creator, proceeded to bend the straight line into a circle; and then to split the one circle into two, intersecting at two points; and one of the two circles he split into seven, the revolutions of heaven being regarded as the motions of the soul. In the first place, it is not right to call the soul a magnitude. For by the soul of the universe Timaeus clearly intends something of the same sort as what is known as mind: he can hardly mean that it is like the sensitive or appetitive soul, whose movements are not circular. But the thinking mind is one and continuous in the same sense as the process of thinking. Now thinking consists of thoughts. But the unity of these thoughts is a unity of succession, the unity of a number, and not the unity of a magnitude. This being so, neither is mind continuous in this latter sense, but either it is without parts or else it is continuous in a different sense from an extended magnitude. For how can it possibly think if it be a magnitude? Will it think with some one or other of its parts: such parts being taken either in the sense of magnitudes or in the sense of points, if a point can be called a part? If it be with parts in the sense of points, and there is an. infinity of these, clearly mind will never reach the end of them; while, if they be taken in the sense of magnitudes, mind will have the same thoughts times without end. But experience shows that we can think a thought once and no more. Again, if it be enough for the soul to apprehend with one or other of its parts, what need is there for it to be moving in a circle or to have magnitude at all? But, if it is necessary to thought that the mind should bring the whole circle into contact, what does the contact of the several parts mean? Again, how will it think that which is divisible by means of that which is without parts, or that which is without parts by means of that which is divisible? It must be mind which is meant by the circle in question. For when mind moves it thinks; when a circle moves it revolves. If, then, thought is a revolution, the circle which has such a revolution must

be mind. But then it will go on thinking of something for ever, for this is required by the eternity of the revolution. To practical thinking there are limits, for it always implies an external end; while speculative thinking is determined in the same way as the logical explanations which express it. Now every explanation consists either in definition or in demonstration. But demonstrations have a premiss for starting-point and reach a kind of goal in the inference or conclusion; while, even if they never reach a conclusion, at all events they do not revert to the starting-point, but with the aid of a succession of middle terms and extremes advance in a straight line. But circular movement returns to the point from which it started. Definitions, too, are all determinate. Besides, if the same revolution recurs again and again, the mind will be obliged to think the same thing again and again. Further, it is a sort of rest or coming to a halt, and not motion, which thinking resembles: and we may say the same of the syllogism. Nor, again, will that which does not move easily, but under constraint, even realise happiness. If the motion of soul be not its essence, it will be an unnatural motion. And the entanglement of the mind in the body without the possibility of release is painful; nay, it is to be avoided, if indeed it is really better for mind to be independent of body, a view commonly expressed and widely accepted. Also it is not clear why the heaven revolves in a circle; seeing that circular motion is neither implied by the essence of soul (that form of movement being indeed merely accidental to it), nor due to the body: on the contrary it is rather the soul which causes the motion of the body. Besides, we are not even told that it is better so: yet surely the reason why God made the soul revolve in a circle ought to have been that movement was better for it than rest, and this form of movement better than any other.

But such an enquiry as this belongs more appropriately to a different subject: so let us dismiss it for the present. We may, however, note here another absurdity which is involved in this as in most other theories concerning the soul. They attach the soul to, and enclose it in, body, without further determining why this happens and what is the condition of the body. And yet some such explanation would seem to be required, as it is owing to their relationship that the

one acts, the other is acted upon, that the one is moved, and the other causes it to move; and between two things taken at random no such mutual relations exist. The supporters of such theories merely undertake to explain the nature of the soul. Of the body which is to receive it they have nothing more to say: just as if it were possible for any soul taken at random, according to the Pythagorean stories, to pass into any body. This is absurd, for each body appears to have a distinctive form or shape of its own. It is just like talking of a transmigration of carpentry into flutes: for the craft must employ the right tools and the soul the right body.

There is yet another opinion concerning soul which has come down to us, commending itself to many minds as readily as any that is put forward, although it has been severely criticised even The theory in the popular discussions of the present day. The soul is asserted to be a kind of harmony, for harmony is on this view a blending or combining of opposites, and the components of the body are opposites. And yet this harmony must mean either a certain proportion in the components or else the combining of them; and the soul cannot possibly be either of these. Furthermore, to cause motion is no attribute of a harmony: yet this function more than any other is all but universally assigned to soul. Again, it is more in harmony with the facts to apply the term harmony to health or bodily excellence generally than to soul, as is very clearly seen when we try to assign to a harmony of whatever kind the affections or functions of the soul: it is difficult to harmonise them.

Further, if we use the word harmony with a twofold application; first, and in its most natural sense, of those magnitudes which have motion and position, to denote the combining meanings of them into a whole, when they are so closely fitted together that they do not admit between them anything of the same kind; and then in a secondary sense to denote the proportion subsisting between the components of a mixture: in neither sense is it reasonable to call soul a harmony. The view which regards it as a combining of the parts of the body is singularly

open to criticism. For there are many combinings of the parts, and they combine in many ways. What part, then, is that whose combining with the rest we must assume to be the intellect, and in what way does it combine? Or again, what of the sensitive and appetitive faculties? But it is equally absurd to regard the soul as the proportion determining the mixture. For the elements are not mixed in the same proportion in flesh as in bone. Thus it will follow that there are many souls, and that, too, all over the body, if we assume that all members consist of the elements variously commingled and that the proportion determining the mixture is a harmony, that is, soul. This is a question we might ask Empedocles; who says that each of the parts is determined by a certain proportion. Is the soul, then, this proportion, or is it rather developed in the frame as something distinct? And, further, is it a mixture at random or a mixture in the right proportion which he ascribes to Love: and, if the latter, is Love the proportion itself or something other than the proportion and distinct from it? Such, then, are the difficulties involved in this view. On the other hand, if soul is something distinct from the mixture, how comes it that it is destroyed simultaneously with the disappearance of the quiddity of the flesh and of the other parts of the animal? And, further,. assuming that each of the separate parts has not a soul of its own, unless the soul be the proportion of their admixture, what is it that perishes when the soul quits the body?

From what has been said it is clear that the soul cannot be a harmony and cannot revolve in a circle. But incidentally it can, as we have seen, move and set itself in motion: for instance, the body in which it is may move, and be set in motion by the soul: otherwise it cannot possibly move from place to place. The question whether the soul is moved would more naturally arise in view of such facts as the following. The soul is said to feel pain and joy, confidence and fear, and again to be angry, to perceive and to think; and all these states are held to be movements: which might lead one to infer that soul itself is moved. But this is no necessary inference. For suppose it ever so true that to feel pain

or joy and to think are movements, that to experience each of these is to be moved and that the movement is due to the soul: suppose that to be angry, for instance, or to be afraid means a particular movement of the heart, and that to think means a movement of this or of some other part, some of these movements being movements of locomotion, others of qualitative change (of what sort and how produced does not concern us here): yet, even then, to speak of the soul as feeling anger is as if one should say that the soul weaves or builds. Doubtless it would be better not to say that the soul pities or learns or thinks, but that the man does so with the soul: and this, too, not in the sense that the motion occurs in the soul, but in the sense that motion sometimes reaches to, sometimes starts from, the soul. Thus, sensation originates in particular objects, while recollection, starting from the soul, is directed towards the movements or traces of movements in the Intellect: Sense-organs. But intellect would seem to be developed as a self-existing substance and to be imperishable. perishable. For, if anything could destroy it, it would be the feebleness of age. But, as things are, no doubt what occurs is the same as in the case of the sense-organs. If an aged man could procure an eye of the right sort, he would see just as well as a young man. Hence old age must be due to an affection or state not of the soul as such, but of that in which the soul resides, just as is the case in intoxication and disease. In like manner, then, thought and the exercise of knowledge are enfeebled through the loss of something else within, but are in themselves impassive. But reasoning, love and hatred are not attributes of the thinking faculty but of its individual possessor, in so far as he possesses it. Hence when this possessor perishes, there is neither memory nor love: for these never did belong to the thinking faculty, but to the composite whole which has perished, while the intellect is doubtless a thing more divine and is impassive.

From the foregoing it is clear that the soul is incapable of motion; and, if it is not moved at all, clearly it does not move itself. Now of all the views that have been put forward by far the most irrational is that which makes the soul a self-moving number. Its supporters are involved in

many impossibilities, not only in those which arise from attributing motion to the soul, but also in others of a special character due to calling it a number. For how are we to conceive of a unit, a thing which is without parts or differences, as in motion? By what would it be moved, and in what way? For if it is capable of imparting motion as well as of being moved, it must admit differences. Further, since they say that a line by its motion generates a surface and that a point by its motion generates a line, the movements of the units will also be lines, for a point is a unit having position. But the number of the soul must, from the nature of the case, be somewhere and have position. Again, if you subtract a number or unit from a number, a different number remains: whereas plants and many animals continue to live when divided and seem to have specifically the same soul in each segment. Besides, it would seem to make no difference whether we Say units or tiny particles. For if the little round atoms of Democritus be converted into points and only their sum-total be retained, in such sum-total there will still be a part which moves and a part which is moved, just as there is in that which is extended. The truth of this statement does not depend upon the size of the atoms, whether great or small, but upon the fact that there is a sum-total or quantity of them. Hence there must be something to set the units in motion. But if in the animal the part which causes motion is the soul, then it is so likewise in the number: so that it will not be both that which causes motion and that which is moved which is the soul, but that which causes motion only. How then can this cause of motion be a unit? For if it were so there must be some difference between it and the other units. But what is there to differentiate points which are units, except position? If, then, the units, that is the points, in the body are distinct from the units of soul, the units of soul will be in the same place as the points, for each unit will occupy the space of a point. And yet if two things can be in the same place, why not an infinite number? When the place which things occupy is indivisible, the things themselves are also indivisible. If, on the other hand, the number of the soul consists of the ar points in the body, or if the soul is the number of such points, why are not all bodies possessed of soul? For in all bodies there

would seem to be points: nay, an infinity of points. And, further, how can the points be separated and set free from the bodies to which they belong; unless, indeed, we are prepared to resolve lines into points?

It comes to this, then, as we have said, first, that this view coincides with that which makes of the soul a body composed of fine particles; next, that its agreement with Democritus as to the manner in which he makes the body to be moved by the soul gives it an especial absurdity of its own. If the soul resides in the whole sentient body, on the assumption that the soul is a sort of body it necessarily follows that two bodies occupy the same space. Those who call the soul a number have to assume many points in the one point, or else that everything corporeal has a soul; unless the number that comes to exist in the body is a different number, quite distinct from the sum of the points already present in the body. Hence it follows that the animal is moved by the number in the same way precisely as we said Democritus moved it. For what difference does it make whether we speak of small round atoms or large units, or indeed of units in spatial motion at all? Either way it is necessary to make the motion of the animal depend on the motion of these atoms or units. Such, then, are some of the difficulties confronting those who join motion and number: and there are many others, since it is impossible that the conjunction of motion with number should form even an attribute, much less the definition, of soul. This will be evident if we try to deduce from this definition the affections and functions of the soul; its reasonings, perceptions, pleasures, pains, and so forth. For, as we said above, from the account given it is difficult even to divine what these functions are.

Three modes of defining the soul have come down to us: some defined it as that which, in virtue of its self-motion, is most capable of causing motion; others as the body which consists of the finest particles, or which is more nearly incorporeal than anything else. And we have pretty fully explained what difficulties and inconsistencies these views present. It remains to consider what is meant by saying that the soul is composed of the

elements. Soul, we are told, is composed of the elements in order that it may perceive and know each several thing. But this theory necessarily involves many impossibilities. For it is assumed that like is known by like; which implies that soul is identical with the things that it knows. These elements, however, are not all that exists: there are a great, or perhaps we should say rather, an infinite number of other things as well, namely, those which are compounded of the elements. Granted, then, that it is possible for the soul to know and to perceive the constituent elements of all these composite things, with what will it know or perceive the compound itself? I mean, what God or man is; what flesh or bone is: and so likewise with regard to any other composite thing. For it is not elements taken anyhow which constitute this or that thing, but only those which are united in a given proportion or combination, as Empedocles says of bone:—

"Then did the bounteous earth in broad-bosomed crucibles win out of eight parts two from the sheen of moisture and four from the fire-god; and the bones came into being all white."

It is therefore of no use for the elements to be in the soul, unless it also contains their proportions and the mode of combining them. For each element will know its like, but there will be nothing to know bone or man, unless these also are to be present in the soul: which, I need hardly say, is impossible. Who would ask if stone or man resides in the soul? And similarly with that which is good and that which is not good: and so for all the rest.

Being, again, is a term which has various meanings, signifying sometimes the particular thing, sometimes quantity or quality or any other of the categories which have been already determined. Is the soul to be derived from all of these, or not? It cannot be: the general opinion is that there are no elements common to all the categories. Does the soul, then, consist of those elements alone which are the elements of substances? How then does it know each of the other categories? Or will they say that each summum genus has special elements and principles of its own, and that the soul is composed of these? Then soul will be at once quantity, quality and substance. But it is impossible from the elements of

quantity to derive substance or anything but quantity. These, then, and others like them are the difficulties which confront those who derive soul from all the elements. There is a further inconsistency in maintaining that like is unaffected by like and yet at the same time that like perceives like and knows like by like. But they assume that perceiving is a sort of being acted upon or moved. And the same holds of thinking and knowing.

Of the many problems and difficulties involved in holding with Empedocles that each thing is known through corporeal elements and by reference to its like [what has just been said ts evidence].— For, it would seem, whatever within the bodies of animals consists entirely of earth, such as bones, sinews, hair, perceives nothing at all, and consequently cannot perceive its like; as in consistency it should. Moreover, each one of the elemental principles will have a far larger share of ignorance than of intelligence; there being many things of which it will be ignorant and only one which it will know: in fact, it will be ignorant of all besides that one. It follows, for Empedocles at any rate, that God is quite the most unintelligent of beings. There is one of the elements, viz. Strife, which he, and he alone, will not know, while mortal things, being composed of all the elements, will know them all. And in general, seeing that everything is either an element or derived from one or more or all elements, why should not all things that exist have soul? For they must certainly know one thing or some things or all. It might further be asked what it is that gives them unity. For the elements, at all events, correspond to matter. That other principle, whatever it be, which holds them together, is supreme. Yet it is impossible that anything should be superior to the soul and overrule it; and still more impossible that anything should overrule intelligence. This, it may reasonably be held, has a natural priority and authority. Yet we are told that the elements are prior to all other things that exist.

And it is characteristic, alike of those who derive the soul from the elements on the ground of perception and knowledge, and of those who define it as the thing most capable of causing motion,

that their assertions do not apply to soul in every form. For not all sentient beings can cause motion; some animals are seen to be stationary in one place. And yet it is at all events a received view that this, namely, change of place, is the one form of motion which the soul imparts to the animal. Similarly with those who derive intelligence and the faculty of sense from the elements. For plants are found to live without any share in locomotion or sensation, and many animals to be destitute of thought. If we waive this point and assume intellect to be a part of the soul, and the faculty of sense likewise, even then their statements would not apply generally to all soul, nor to the whole of any one soul. The account given in the so-called Orphic poems is open to the same strictures. For the soul, it is there asserted, enters from the universe in the process of respiration, being borne upon the winds. Now it is impossible that this should be so with plants or even with some animals, seeing that they do not all respire: a point which the upholders of this theory have overlooked. And if the soul is to be constructed out of the elements, there is no need to employ them all, the one of a pair of contraries being sufficient to discern both itself and its opposite. For by that which is straight we discern both the straight and the crooked, the carpenter's rule being the test of both. On the other hand that which is crooked is not a test of itself or of that which is straight.

There are some, too, who say that soul is interfused throughout the universe: which is perhaps why Thales supposed all things to be full of gods. But this view presents some difficulties. For why should the soul not produce an animal, when present in air or fire, and yet do so when present in the compounds of these elements: and that, too, though in the former case it is believed to be purer? One might also enquire why the soul present in air is purer and more immortal than soul in animals. Whichever of the two suppositions open to us we adopt is absurd and irrational. To speak of fire or air as an animal is very irrational; and on the other hand

not to call them animals, if they contain soul, is absurd. But it would seem that the reason why they suppose soul to be in these elements is that the whole is homogeneous with its parts. So that they cannot help regarding universal soul as also homogeneous with the parts of it in animals, since it is through something of the surrounding element being cut off and enclosed in animals that the animals become endowed with soul. But if the air when split up remains homogeneous, and yet soul is divisible into non-homogeneous parts, it is clear that, although one part of soul may be present in the air, there is another part which is not. Either, then, soul must be homogeneous, or else it cannot be present in every part of the universe.

From what has been said it is evident that it is not because the soul is compounded of the elements that knowledge belongs to it, nor is it correct or true to say that the soul is moved. Knowledge, however, is an attribute of the soul, and so are perception, opinion, desire, wish and appetency generally; animal locomotion also is produced by the soul; and likewise growth, maturity and decay. Shall we then say that each of these belongs to the whole soul, that we think, that is, and perceive and are moved and in each of the other operations act and are acted upon with the whole soul, or that the different operations are to be assigned to different parts? And what of life itself? Does it reside in any single one or more or all of these parts? Or has it a cause entirely distinct? Now some say that the soul is divisible and that one part of it thinks, another desires. What is it then which holds the soul together, if naturally divisible? Assuredly it is not the body: on the contrary, the soul seems rather to hold the body together; at all events, when it has departed, the body disperses in air and rots away. If, then, the unity of soul is due to some other thing, that other thing would be, properly speaking, soul. We shall need, then, to repeat the enquiry respecting it also, whether it is one or manifold. For, if it has unity, why not attribute unity to the soul itself at the outset? If, however, it be divisible, then again reason will go on to ask what it is that holds together, and so the enquiry will go on to infinity. It might also be asked what power each of the parts of the soul

exercises in the body. For, if the entire soul holds together the whole body, then each of its parts ought properly to hold together some part of the body. But this seems impossible. For it is difficult even to conjecture what part the intellect will hold together or how it can hold any part together. It is found that plants, and among animals certain insects or annelida, live when divided, which implies that the soul in their segments is specifically, though not numerically, the same. At any rate, each of the two segments retains sentience and the power of locomotion for some time: that they do not continue to do so is not surprising, as they lack the organs requisite to maintain their nature. But none the less all the parts of the soul are contained in each of the two segments, and the two halves of the soul are homogeneous alike with one another and with the whole; a fact which implies that, while the parts of the soul are inseparable from one another, the soul as a Whole is divisible. It would seem that the vital principle in plants. jin plants also is a sort of soul. For this principle is the only one common to plants and animals; and, while it can be separated from the sensitive principle, no being which has sensation is without it.

So much for the theories of soul handed down by our predecessors. Let us, then, make a fresh start and try to determine what soul is and what will be its most comprehensive definition. Now there is one class of existent things which we call substance, including under the term, firstly, matter, which in itself is not this or that; secondly, shape or form, in virtue of which the term this or that is at once applied; thirdly, the whole made up of matter and form. Matter is identical with potentiality, form with actuality. And there are two meanings of actuality: knowledge illustrates the one, exercise of knowledge the other. Now bodies above all things are held to be substances, particularly such bodies as are the work of nature; for to these all the rest owe their origin. Of natural bodies some possess life and some do not: where by life we mean the power of self-nourishment and of independent growth and decay. Consequently every natural body possessed of life must be substance, and substance of the composite order. And since in fact we have here body with a certain attribute, namely, the possession of life, the body will not be the soul: for the body is not an attribute of a subject, it stands rather for a subject of attributes, that is, matter. It must follow, then, that soul is substance in the sense that it is the form of a natural body having in it the capacity of life. Such substance is actuality. The soul,

therefore, is the actuality of the body above described. But the term "actuality" is used in two senses; in the one it answers to knowledge, in the other to the exercise of knowledge. Clearly in this case it is analogous to knowledge: for sleep, as well as waking, implies the presence of soul; and, whilst waking is analogous to the exercise of knowledge, sleep is analogous to the possession of knowledge without its exercise; and in the same individual the possession of knowledge comes in order of time before its exercise. Hence soul is the first actuality of a natural body having in it the capacity of life. And a body which is possessed of organs answers to this description.—We may note that the parts of plants, as well as those of animals, are organs, though of a very simple sort: for instance, a leaf is the sheath of the pod and the pod of the fruit. The roots, again, are analogous to the mouths of animals, both serving to take in nourishment. If, then, we have to make a general statement touching soul in all its forms, the soul will be the first actuality of a natural body furnished with organs. Hence there is no need to enquire whether soul and body are one, any more than whether the wax and the imprint are one; or, in general, whether the matter of a thing is the same with that of which it is the matter. For, of all the various meanings borne by the terms unity and being, actuality is the meaning which belongs to them by the fullest right.

It has now been stated in general terms what soul is, namely, substance as notion or form. And this is the quiddity of such and such a body. Suppose, for example, that any instrument, say, an axe, were a natural body, its actuality would be its substance, would in fact be its soul. If this were taken away, it would cease, except in an equivocal sense, to be an axe. But the axe is after all an axe. For it is not of a body of this kind that the soul is the quiddity, that is, the notion or form, but of a natural body of a particular sort, having in itself the origination of motion and rest.

Further, we must view our statement in the light of the parts of the body. For, if the eye were an animal, eyesight would be its soul, this being the substance as notion or form of the eye. The eye is the matter of eyesight, and in default of eyesight it is no longer an eye, except equivocally,

like an eye in stone or in a picture. What has been said of the part must be understood to apply to the whole living body; for, as the sensation of a part of the body is to that part, so is sensation as -a whole to the whole sentient body as such. By that which has in it the capacity of life is meant not the body which has lost its soul, but that which possesses it. Now the seed in animals, like the fruit in plants, is that which is potentially such and such a body. As, then, the cutting of the axe or the seeing of the eye is full actuality, so, too, is the waking state; while the soul is actuality in the same sense as eyesight and the capacity of the instrument. The body, on the other hand, is simply that which is potentially existent. But, just as in the one case the eye means the pupil in conjunction with the eyesight, so in the other soul and body together constitute the animal.

Now it needs no proof that the soul—or if it is divisible into parts, certain of its parts—cannot be separated from the body, for there are cases where the actuality belongs to the parts themselves. There is, however, no reason why some parts should not be separated, if they are not the actualities of any body whatever. Again, it is not clear whether the soul may not be the actuality of the body as the sailor is of the ship. This, then, may suffice for an outline or provisional sketch of soul.

But, as it is from the things which are naturally obscure, though more easily recognised by us, that we proceed to what is clear and, in the order of thought, more knowable, we must employ this method in trying to give a fresh account of soul. For it is not enough that the defining statement should set forth the fact, as most definitions do; it should also contain and present the cause: whereas in practice what is stated in the definition is usually no more than a conclusion. For example, what is quadrature? The construction of an equilateral rectangle equal in area to a given oblong. But such a definition expresses merely the conclusion. Whereas, if you say that quadrature is the discovery of a mean proportional, then you state the reason.

We take, then, as our starting-point for discussion that it is life which distinguishes the animate from the inanimate. But the term life is used in various senses; and, if life is present in but a

single one of these senses, we speak of a thing as living. Thus there is intellect, sensation, motion from place to place, the motion concerned with nutrition and, further, decay and growth. Hence it is that all plants are supposed to have life. For apparently they have within themselves a faculty and principle whereby they grow and decay in opposite directions. For plants do not grow upwards without growing downwards; they grow in both directions equally, in fact in all directions, as many as are constantly nourished and therefore continue to live, so long as they are capable of absorbing nutriment. This form of life can be separated from the others, though in mortal creatures the others cannot be separated from it. In the case of plants the fact is manifest: for they have no other faculty of soul at all.

It is, then, in virtue of this principle that all living things live, Sensation Wether animals or plants. But it is sensation primarily which constitutes the animal. For, provided they have sensation, even those creatures which are devoid of movement and do not change their place are called animals and are not merely said to be alive. Now the primary sense in all animals is touch. But, as the nutritive faculty may exist without touch or any form of sensation, so also touch may exist apart from the other senses. By nutritive faculty we mean the part of the soul in which even plants share. Animals, however, are found universally to have the sense of touch: why this is so in each of the two cases will be stated hereafter.

For the present it may suffice to say that the soul is the origin of the functions above enumerated and is determined by them, namely, by capacities of nutrition, sensation, thought, and by motion. But whether each one of these is a soul or part connection of a soul and, if a part, whether it is only logically functions. distinct or separable in space also is a question, the answer to which is in some cases not hard to see: other cases present difficulties. For, just as in the case of plants some of them are found to live when divided and separated from each other (which implies that the soul in each plant, though actually one, is potentially several souls), so, too, when insects or annelida are cut up, we see the same thing happen with other varieties of soul: I mean, each of the segments has sensation and moves from place

to place, and, if it has sensation, it has also imagination and appetency. For, where there is sensation, there is also pleasure and pain: and, where these are, desire also must of necessity be present. But as regards intellect and the speculative faculty the case is not yet clear. It would seem, however, to be a distinct species of soul, and it alone is capable of separation from the body, as that which is eternal from that which is perishable. The remaining parts of the soul are, as the foregoing consideration shows, not separable in the way that some allege them to be: at the same time it is clear that they are logically distinct. For the faculties of sensation and of opinion taken in the abstract are distinct, since to have sensation and to Opine are distinct. And so it is likewise with each of the other faculties above mentioned. Again, while some animals possess all these functions, others have only some of them, others only one. It is this which will differentiate animal from animal. The reason why this is so must be investigated hereafter. The case is similar with the several senses: some animals have all of them, others some of them, others again only one, the most indispensable, that is, touch.

Now"that by which we live and have sensation" is a phrase with two meanings, answering to the two meanings of "that by which we know" (the latter phrase means, firstly, knowledge and, secondly, soul, by either of which we say we know). Similarly that by which we have health means either health itself or a certain part, if not the whole, of the body. Now of these knowledge and health are the shape and in some sort form, the notion and virtual activity, of that which is capable of receiving in the one case knowledge, in the other health: that is to say, it is in that which is acted upon or conditioned that the activity of the causal agencies would seem to take effect. Now the soul is that whereby primarily we live, perceive, and have understanding: therefore it will be a species of

notion or form, not matter or substratum. Of the three meanings of substance mentioned above, form, matter and the whole made up of these two, matter is potentiality and form is actuality. And, since the whole made up of the two is endowed with soul, the body is not the actuality of soul, but soul the actuality of a particular body. Hence those are right who regard the soul as not independent of body and yet at the same time as not itself a species of body. It is not body, but something belonging to body, and therefore resides in body and, what is more, in such and such a body. Our predecessors were wrong in endeavouring to fit the soul into a body without further determination of the nature and qualities of that body: although we do not even find that of any two things taken at random the one will admit the other. And this result is what we might expect. For the actuality of each thing comes naturally to be developed in the potentiality of each thing: in other words, in the appropriate matter. From these considerations, then, it is manifest that soul is a certain actuality, a notion or form, of that which has the capacity to be endowed with soul.

Of the powers of soul above mentioned, namely, those of nutrition, appetency, sensation, locomotion and understanding, some living things, as we remarked, possess all, others some, others again only one. Plants possess the nutritive faculty only: other things along with this have Appetency sensation; and, if sensation, then also appetency: where under appetency we include desire, anger and wish. But:" all animals have at least one sense, touch: and, where sensation is found, there is pleasure and pain, and that which causes pleasure and pain; and, where these are, there also is desire, desire being appetite for what is pleasurable. Again, they have a sensation concerned with nutriment, touch being such a sense. For it is by what is dry and moist, hot and cold, that all living things are nourished (and these qualities are perceived by touch, whereas the other sensibles are not, except incidentally): for sound, colour and odour contribute nothing to nutriment, while flavour

is one of the tangible objects. Hunger again, and thirst are forms of desire, the one for what is hot or dry, the other for what is cold or moist. Flavour is, as it were, the seasoning of these. We will deal with these in detail hereafter: at present let it suffice to say that all animals which have the sense of touch are also endowed with appetency. Whether they have imagination is not clear: this, too, must be considered later. Some have in addition the power of locomotion. Others—that is to say, man and any other species like man or, possibly, superior to him—have also the thinking faculty and intellect.

From this it is clear that there is one definition of soul exactly as there is one definition of figure: for there is in the of soul, os one case no figure excepting triangle, quadrilateral and the rest,.nor is there in the other any species of soul apart from those above mentioned. Again, a definition might be constructed which should apply to all figures, but not specially to any species of figure. And similarly with the species of soul above enumerated. Hence it would be absurd here as elsewhere to seek a general definition which will not be properly a definition of anything in existence and will not be applicable to the particular irreducible species before us, to the neglect of the definition which is so applicable.

The types of soul resemble the series of figures. For, alike in figures and in things animate, the earlier form exists potentially in the later, as, for instance, the triangle potentially in the quadrilateral, and the nutritive faculty in that which has sensation. So that we must examine in each case separately, what is the soul of plant, of man or of beast. Why they are related in this order of succession remains to be considered. There is no sensitive faculty apart from the nutritive: and yet the latter exists without the former in plants. Again, none of the other senses is found apart from touch; while touch is found apart from the others, many animals having neither sight nor hearing nor sense of smell. Also of those which possess sensation, some can move from place to place, others cannot.

Lastly and most rarely, they have the reasoning faculty and thought. For those perishable creatures which possess reason are endowed with all the other species of soul, but not all those which possess each of the other faculties have reason. Indeed, some of them have not even imagination, while others live by imagination alone. As for the speculative intellect, it calls for a separate discussion. Meanwhile it is clear that an account of the several faculties is at the same time the most appropriate account of soul.

The enquirer who approaches this subject must ascertain what each of these faculties is before he proceeds to investigate procedure. the questions next in order and so forth. But if we are asked to state what each of these is; that is to say, what the cognitive, sensitive and nutritive faculties respectively are, we must begin by stating what the act of thinking is and what the act of sensation is. For activities and functions are logically prior to faculties. But, if so, and if a study of the correlative objects should have preceded, these objects will for the same reason have to be defined first: I mean, nutriment and the sensible and intelligible. Consequently we have first to treat of nutriment and of generation.

The nutritive soul belongs to other living things as well as man, being the first and most widely distributed faculty, in virtue of which all things possess life. Its functions are reproduction and assimilation of nutriment. For it is the most natural function in all living things, if perfect and not defective or spontaneously generated, to reproduce their species; animal producing animal and plant plant, in order that they may, so far as they can, share in the eternal and the divine. For it is that which all things yearn after, and that is the final cause of all their natural activity. Here final cause is an ambiguous term, which denotes either the purpose for which, or the person for whom, a thing is done. Since, then, individual things are incapable of sharing continuously in the eternal and the divine, because nothing in the world of perishables can abide numerically one and the same, they partake in the eternal and

divine, each in the only way it can, some more, some less. That is to say, each persists, though not in itself, yet in a representative which is specifically, not numerically, one with it.

Now the soul is cause and origin of the living body. But cause and origin are terms used in various senses: accordingly soul is cause in the three senses of the word cause already determined. For the soul is the cause of animate bodies as being in itself the origin of motion, as final cause and as substance. Clearly it is so as substance, substance being the cause of all existence. And for living things existence means life, and it is the soul which is the cause and origin of life. Furthermore, actuality is the notion or form of that which has potential existence. Manifestly, too, the soul is final cause. For nature, like intelligence, acts for a purpose, and this purpose is for it an end. Such an end the soul is in animals, and this in the order of nature, for all the natural bodies are instruments of soul: and this is as true of the bodies of plants as of those of animals, shewing that all are means to the soul as end; where end has two senses, the purpose for which and the person for whom. Moreover, the soul is also the origin of motion from place to place, but not all living things have this power of locomotion. Qualitative change, also, and growth are due to soul. For sensation is supposed to bea sort of qualitative change, and nothing devoid of soul has sensation. The same holds of growth and decay. For nothing undergoes natural decay or growth except it be nourished, and nothing is nourished unless it shares in life.

Empedocles is mistaken in adding that in plants, in so far as they strike their roots downwards, growth takes place because the earth in them has a natural tendency in this direction and that, when they shoot upwards, it is because the fire in them has a similar tendency upwards. He is wrong in his view of up and down. For up and down are not the same for all individuals as for the universe. On the contrary, the roots of plants correspond to the heads of animals, if we are to

make identity and diversity of organs depend upon their functions. Besides, what is it that holds together the fire and the earth, tending, as they do, in opposite directions? For they will be rent asunder, unless there is something to prevent it: while, if there is, it is this which is the soul and the cause of growth and nourishment.

Some hold the nature of fire to be singly and solely the cause of nourishment and growth. For it would seem that fire is the only body or element which of itself is nourished and grows. Hence fire might be supposed to be the operative cause, both in plants and animals. Whereas, though it is in a sense a joint cause, it is not a cause absolutely: it is rather the soul which is so. For fire goes on growing to infinity, as long as there is fuel to be consumed, but in natural wholes there is always a limit or proportion which determines growth and size. But this belongs to the soul and not to fire, to form rather than' to matter.

The nutritive faculty of the soul being the same as the reproductive, it is necessary first to give a definition of nutriment. For it is by the nutritive function that this faculty is separated off from the others. The common view is that contrary is nutriment to contrary; though not in every case, but wherever each of two contraries is not only generated by, but derives growth from, the other. For many things are derived from one another, but not all of them are quantities: thus the sick man becomes well. But it is found that even the contraries supposed to derive growth from each other are not fed by one another in the same way: while water serves to feed fire, fire is not nutriment to water. It would seem, then, that it is in the simple bodies above all that of two contraries one is nutriment and the other is nourished. Yet here is a difficulty. It is said by the one side that like is nourished by, as well as derives its growth from, like; while the others, again, as we explained, hold that contrary is nourished by contrary, on the ground that like cannot be affected by like, while food undergoes change and is digested. Now change is always in the direction of the opposite, or of the intermediate state. Further, nutriment is acted upon by that which it nourishes, and not the latter by the former: just as

the carpenter is not affected by his material, but on the contrary the material by the carpenter. The carpenter merely passes to activity from inaction. But it makes a difference whether by nutriment we mean the final, or the primary, form of what is added. If both are nutriment, the one as undigested, the other as digested, it will be possible to use the term nutriment in conformity with both theories. For, in so far as it is undigested, contrary is nourished by contrary: and, in so far as it is digested, like by like. So that clearly both sides are in a manner partly right and partly wrong. But, since nothing is nourished unless it possesses life, that which is nourished must be the animate body as such: so that nutriment also is relative to the animate being which it nourishes: and this not incidentally merely.

There is, however, a difference between nutritivity and conducivity to growth. In so far as the animate thing is quantitative, what is taken promotes growth; in so far as it is a definite individual, what is taken nourishes. For the animate thing preserves its substance or essential nature and exists as long as it is nourished: and it causes the production, not of that which is nourished, but of another individual like it. Its essential nature already exists, and nothing generates itself, it only maintains its existence. Hence the above described principle of the soul is the power to preserve in existence that which possesses it in so far as it is a definite individual, while nutrition prepares it for activity. Therefore it cannot live when deprived of nutriment. There are, then, these three things, that which is nourished, that with which it is nourished, and that which nourishes it. The last of the three is the primary soul, that which is nourished is the body which contains the soul, that wherewith it is nourished is nutriment. As, however, it is right to name all things from the end they subserve, and the end here is reproduction of the species, the primary soul is that which is capable of reproducing the species. That with which the living thing is nourished may be understood in two senses, just as that with which one steers may mean the hand or the rudder; the former, the hand, both causing motion and being moved, the latter, the rudder, being simply moved. Now it is necessary that all food should be capable of digestion, and digestion is promoted by heat; this explains why every animate thing has warmth. This, then, is an outline of what nutriment is. It must be more clearly defined hereafter in the discussion devoted specially to it.

Now that these points have been determined, let us proceed to a general discussion of all sensation. As above remarked, sensation consists in being moved and acted upon, for it is held to be a species of qualitative change. Some add that like is in fact acted upon by like. How far this is possible or impossible we have explained in the general discussion of action and passivity. The question arises why there is no sensation of the senses themselves: that is, why they produce no sensation apart from external sensibles, though the senses contain fire, earth and the other elements, which are the objects of sensation either in themselves or through their attributes. Evidently it Sensation follows that the faculty of sensible perception exists not in activity, but only in potentiality. Hence it must be here as with the fuel which does not burn of and in itself without something to make it burn; otherwise it would kindle itself and would have no need of the fire which is actually existent. Now to have sensation has two meanings: we use the terms hearing and seeing "of that which has the capacity to hear and see, even though it be at the time asleep, just as we do of that which already actually hears and sees. And therefore sensation, too, will have two meanings: it may mean either potential or actual sensation. Similarly with having sensation, whether potential or actual.

Let us then first proceed on the assumption that to be acted Agent ana Upon or moved is identical with active operation. For movement is in fact active operation of some sort, though incomplete, as we have elsewhere explained. But in every case things are acted upon and moved by an agent in actual operation. It follows that in one sense what is acted upon is acted upon by what is like it, in another sense by what is unlike it, as we have explained. That is to say, while being acted upon it is unlike, after it has been acted upon it is like the agent.

We must also draw a distinction in regard to the terms potentiality and actuality: at present we are using them without qualification. For instance, we may use the term wise, firstly, in the sense in which we might speak of man as wise, because man is one of the genus of beings which are wise and have wisdom; secondly, in the sense in which we at once call the man wise who has learnt, say, grammar. Now of these two men each possesses the capacity, but in a different sense: the one because the genus to which he belongs, that is to say, his matter, is potentially wise; the other because he is capable, if he chose, of applying the wisdom he has acquired, provided there is nothing external to hinder. Whereas he who is at the moment exercising his wisdom is in actuality and is wise in the proper sense of the term: for example, he knows the A before him. Thus the first two are both potentially wise: the first becomes wise actually after he has undergone qualitative change through instruction and often after transition from the reverse condition; while in the latter case it is by another kind of transition that the man passes from the mere possession, without the use, of sensation or grammar to the use of it.

To suffer or be acted upon, too, is a term of more than one meaning. Sometimes it means a sort of destruction by the contrary, sometimes it is rather a preservation of what is potentially existent by what is actually existent and like it, so far as likeness holds of potentiality when compared with actuality. For it is by exercise of knowledge that the possessor of knowledge becomes such in actuality: and this either is no qualitative change (for the thing develops into its own nature and actuality), or else is qualitative change of a different sort. Hence it is not right to say that that which thinks undergoes change when it thinks, any more than that the builder undergoes change when he builds. That, then, which works the change from potential existence to actuality in a thinking and intelligent being should properly receive a different name and not be called instruction: while that which learns and is brought from potential to actual knowledge by that which is in actuality and capable of instructing should either not be said to suffer or be acted upon at

all, or else two modes of change should be assumed, one to the negative states and the other to the normal habits and the true nature.

In the sensitive subject the first change is due to the parent: once generated it possesses sensation exactly in the same sense as we possess knowledge. And to have actual sensation corresponds to exercise of knowledge. There is this difference, however, that in the one case the causes of the activity are external: as, for instance, the objects of sight, hearing and the other senses. The reason is that actual sensation is always of particulars, while knowledge is of universals: and these universals are, in a manner, in the soul itself. Hence it is in our power to think whenever we please, but sensation is not in our power: for the presence of the sensible object is necessary. It is much the same with the sciences which deal with sensible objects; and for the same reason, namely, that sensibles are particulars and are external.

But we shall have a further opportunity of making this clear hereafter. For the present let us be content to have established that of the two meanings of potentiality, the one according to which a child might be called potentially a general, and the other according to which a man of full age might be so called, it is the latter which applies to the faculty of sense-perception. But as this distinction has no word to mark it, although the fact and the nature of the distinction have been established, we are compelled to use the terms to suffer or be acted upon and to be qualitatively changed as if they were the proper terms. Now, as has been explained, the sensitive faculty is potentially such as the sensible object is in actuality. While it is being acted upon, it is not yet similar, but, when once it has been acted upon, it is assimilated and has the same character as the sensible object.