Aristotle — On the Soul

1. Book 1
2. Book 2
3. Book 3

Book 1

We regard knowledge as a good and precious thing, but we esteem one sort of knowledge more highly than another either because of the required for its discovery, or because it is concerned with better and more admirable objects: for both these reasons we should rightly assign the investigation of the soul to the first rank. Further, it is supposed that a knowledge of the soul has an important bearing on all truth, and parI ticularly on that of the natural world. For the soul is, as it were, the genetic principle in living things. Our' aim is to investigate and ascertain the essential nature of the soul, and, secondly, to discover those properties which attach to it as accidents. Certain of the latter are supposed to be conditions peculiar to the soul's own nature, and others are thought to be effects produced in living beings by the soul's agency. Now, it is altogether the most difficult problem to arrive at any fixed belief touching the soul. From the fact that the problem is one which is common to other subjects — I mean the problem of finding the essence and real definition of a thing — it might perhaps appear to some that there is a single scientific method which applies to everything whose essence we wish to discover, as deductive proof applies to accidental properties."We shall, therefore, be obliged to make inquiry into this question of scientific method. But if there is no single and general method which applies to the ultimate nature of things, our investigation becomes in that case all the more difficult. And even if the question of method were cleared up, whether its form be that of deductive proof, or analysis, or some other procedure, there still remains a question of great difficulty and uncertainty, viz. from what principles are | we to start our inquiry? For different principles are ■ employed in different subjects, as e.g. in and in plane surfaces. The first necessity, perhaps, is to determine under what genus soul is to be classified and what its nature is — I mean by this the question whether it is an individual I thing and self-subsisting entity, or whether it is a quality or a quantity or classifiable in one of the other categories already enumerated, and further, whether it is a / potentiality or rather an actuality.

For this makes no) slight difference. We must also inquire whether the soul is divisible or whether it is without parts; whether it is an entirety of one sort or not. And if it is not of one sort, we must further ask whether the differences are specific or generic. For nowadays the men who discuss and investigate the soul appear to direct their inquiries merely to the human soul. We must take pains to see whether there is a single definition that applies to the soul, just as e.g. there is a single definition that applies to animal, or whether a different definition is required for each kind of soul, just as a different definition is required for horse, dog, man, god, and we must further inquire) whether the common notion animal' either is nothing' fat all or else comes into existence only after the individual,— a question that might equally well be raised regarding any other general notion. If, however, there are not several souls, but only parts of a single soul, then the further question arises whether we should examine the soul as a whole before we examine the parts. It is also hard to determine which of these parts is in its nature dift'erent from the other and whether we should first investigate the part or the part's function, e.g. whether we should first investigate the process of thought or the faculty of thought, sense-perception or the organ of sense-perception; the same question applies to other cases. Now, supposing that the functions take precedence of the faculties in the order of investigation, a further question might arise here as to whether the complements of the faculties should be investigated before the faculties themselves, e.g. whether the investigation of the sensible object should precede the investigation of the sense-organ, and the object of thought precede the faculty of thought. Not only does the knowledge of the essential nature of a thing seem to be helpful towards' the understanding of the accidental nature and properties of substances, just as in mathematics the knowledge of the essential nature of straight or curved or of a line or surface is helpful in understanding how many right angles are contained in the angles of a triangle, but conversely, the knowledge of accidental properties contributes largely to the understanding of what a thing essentially is.

For when we are able to give an account of the accidental properties of things, as we see them, — either of all these properties or of most of them. — then we are best able to speak also of their essential nature. For the essential nature is the true startingpoint in all deductive proof. And so in the case of definitions where not only no knowledge of the accidental properties is furnished, but where it is not easy even to conjecture what these properties are, it is evident that all such definitions are framed after the fashion of dialectics and are void. A further difficulty presents itself regarding the affections of the soul, viz. whether all these affections are common to the soul and to the body which contains it, or whether there is a something that is the exclusive property of the soul. And it is necessary, though not easy, to solve this difficulty. In most cases the soul apparently neither acts nor is acted upon independently of the body, e.g. in the feelings of anger, courage, desire, or in a word in sense-perception. Thought, however, appears to be a function which more than any other is the exclusive property of the soul. But if thought is a sort of representation in terms of a sense-image, or is impossible without this, then even thought could not exist independently of the body. If, then, there were any function or affection of the soul that were peculiar to it, it would be possible for the soul to exist separate and apart from the If, however, there is nothing which is its exclusive property, it cannot exist apart, but the case is similar to that of a straight line, which, as straight, has many properties, e.g. contact with a bronze globe at a given point, although the quality'straight/ apart from some body, does not touch the globe. For it has no abstract existence, as it is always conjoined with some body. The same thing seems to hold good of the properties of the soul: courage, gentleness, fear, pity, audacity, also joy, love, hate; they are all associated with the body.

For along with these psychical conditions the body is also somewhat affected. A proof of this is the fact that sometimes when great and palpable misfortunes have befallen a man, he is not at all excited or moved to fear; on the other hand, one is sometimes aroused by slight and insignificant mishaps, and then the body swells in rage and is in the same condition as when a man is stirred in anger. But this statement receives still more support from the fact that when nothing has happened which could awaken fear, men exhibit those emotions which characterize a man in fright. And if this is true, it is evident that the emotions are ideas which find expression in the body. So that we have, for example, such definitions as the following:" Anger is a kind of movement of such and such a body, or part, or faculty, under this or that stimulus and due to this or that motive." It is for this reason that the study of the soul belongs to the province of the natural philosopher, either the soul in its entirety or such part of it as has to do with the body. i6 But the naturalist and the speculative philosopher would frame their definitions severally from different standpoints. For example, in reply to the question" What is anger?" the speculative philosopher says it is the desire of retaliation or something of that sort, the naturalist says it is the seething of the pericordial blood or heat; the one has furnished in his answer the matter, the other the form or reason, of the thing. For the notion is the form of a thing, and it is necessary that this notion be embodied in a particular matter, if it is to exist. For instance, the notion of a house is that of a shelter, to protect us against injury from wind and rain and heat; the natural philosopher, however, will call it stones and bricks and wood, while the other grasps the notion embodied in these things and for which they exist. Which of these, now, is the real physical philosopher? Is it the one who busies himself with the matter, but is ignorant of the notion? or is it the inquirer who is occupied with the notion alone? I answer, it is rather the man who combines both of these characters.

But what is the genius of each of these two men? Surely there is nobody who concerns himself merely with the properties of matter that are inseparable and merely as inseparable; but the physical philosopher has to do with all the functions and qualities of body and matter which are of such and such a kind. Such properties as are not subject-matter for the natural philosopher, are dealt with by someone else, in certain instances by a professor of one of the arts, perhaps, as e.g. by a builder or by a physician. But in the case of properties which are inseparable, although they attach to no particular body and may be abstractly regarded, with these the mathematician is concerned; and in so far as the qualities are regarded as abstract or transcendent entities, the metaphysician is concerned with them. But we must now return to the point from which our discussion digressed. We were saying that the properties of the soul do not exist apart from the physical matter of living things, in which such qualities as courage and fear are expressed, and are not to be regarded as a line or surface. In our inquiry into the soul it is necessary for us, as we proceed, to raise such questions as demand answers; we must collect the opinions of those who have had anything to say touching the soul's nature, in order that we may accept their true statements and be on our guard against their errors. The initial step in our inquiry will be to set forth those attributes which are currently supposed to inhere in the soul's nature. Animate nature is thought to be different from the inanimate mainly in two particulars, viz. in movement and senseJ perception. And these, I may say, are the two traditional characteristics of the soul which we have received from earlier writers. Some of these writers, indeed, affirm that motion is the first and foremost characteristic of the soul, and in the belief that what is itself unmoved cannot impart motion to anything else, they suppose that the soul is a moving entity. This is the reason why Democritus declares the soul to be a sort of fire or warm element.

He asserts that, although atomic structures are infinite in variety, both fire and soul are composed of spherical atoms, similar to the particles, as we call them, seen in the air when sunbeams stream through a doorway, and these atoms, as collective seed-particles, he calls the elements of the universe. Leucippus also holds a similar view. It is the spherical atoms, he says, that constitute the soul, because such forms can most easily penetrate through everything, and, being themselves in motion, can move everything else, the theory of these philosophers being that the is the principle which imparts motion to animals. It is for this reason too that they regard respiration as the function that fixes life's limit. They think that the surrounding air presses together and expels the atomic bodies, which, because they are themselves never at rest, impart motion to animals, but that relief comes through respiration, because similar particles thereby enter into the body from without. These latter, by restraining the contracting and condensing element, prevent the spherical atoms which are already in animals from being entirely expelled. So long as they can do this, life continues. The theory which has been handed down from the ly,thagoreans appears to have the same import. For some members of this school maintain that the sun-motes in the air are the soul; others declare that the soul is the principle which sets these in motion. They refer to these particles in their theory, because the particles appear to be in constant motion, even when there is a complete calm. The philosophers who regard the soul as a self-moved principle come to the same conclusion. For they all seem to regard motion as the most characteristic attribute of the soul, and while everything else is moved by the soul, the soul is self-moved. They came to this conclusion because they observed that nothing sets anything else in motion without being itself in motion. In a similar spirit Anaxagoras also declares the soul to be the principle of motion, and this view is held by such others, if there are any, as assert that Reason sets the All in Anaxagoras does not, however, quite agree with Democritus. For Democritus absolutely identifies soul with reason, and considers truth to be that which appears to the senses.

Consequently, Homer is right in singing of Hector that he lay" thinking awry." Democritus does not employ reason as a specific faculty for the apprehension of truth, but asserts that soul and reason are identical. Anaxagoras, however, is less clear on this point. For although he says in many passages that reason is the cause of the beautiful and the true, in other passages he says that reason is the same as the soul, for it is found in all animals, great and small, high and low. Eeason, however, in the sense of intelligence, is not found equally in all animals, nor even in all men. Such philosophers as fix their attention on movement as the main fact in animate creation conceive of the soul as the most mobile principle. On the other hand, such philosophers as emphasize the knowledge and perception of reality, define the soul as the principle of things, some holding there are several such principles, others that this psychical principle is the only one. Empedocles, for instance, regards the soul as composed of all the elements, and he asserts that each of these elements is a soul. He says:" Earth we apprehend by earth, water by water, And air divine by air, destructive fire by fire, And love we know by love, sad hate by hate." In this way, too, Plato in his constructs n the soul out of the elements; for we know like by like, and things are composed of elemental principles. A similar theory is given in his Discourses on where he defines an animal, regarded absolutely, as a structure derived from the idea of unity and the primary elements length, breadth, and thickness; other things are similarly fashioned. Again, in a different way, Plato defines reason as unity, and science as two;. for the latter moves towards unity in a single course. He also defines opinion as the number of a plane surface and sense-perception as the number of a solid. Numbers were declared to be the actual forms and first principles of things and to be composed of the elements. But things are discerned partly by reason, partly by science, partly by opinion, and partly by sense-perception. Numbers, however, are the forms of things.

Since the soul was regarded by these Platonists as at once / the principle of motion and the principle of knowledge, some of them included both these ideas in their definition, and explained the soul as a self-moving These philosophers differ, however, in regard to the kind and number of their principles. The most far-reaching difference is that between the philosophers who regard the elements as corporeal and those who regard them as incorporeal. There are others who define fl the elements as a composite of corporeal and incorporeal. They differ also in regard to the number of the elements, some believing there is one only, and others that there are several, and their definitions of the soul vary with their theories of the elements. Amongst the primal elements they classified, not unreasonably, the principle of inherent movement. And so some philosophers held the soul to be fire; for fire is the finest and most nearly incorporeal of all the elements, and furthermore, it most readily receives and imparts motion. Democritus has explained in a very neat way the cause of these phenomena. Soul and reason, he says, are identical, and belong to the primary and indivisible bodies, and are, furthermore, the principle of motion by virtue of their particles and atomic forms. Amongst these atomic forms, he regards the spherical as the most easily moved, and says that reason and fire are of this sort. Anaxagoras, on the other hand, appears to say that the soul and reason are different, as we remarked above, and yet he employs them as essentially one, except that he regards reason as more than anything else the initial principle of the world. At any rate he asserts that reason is the only entity which is absolute, unniixed, and pure. But he ascribes both attributes of knowledge and motion to the same principle, affirming that reason sets the universe in motion. Thales also, according to the traditional stories' of him, appears to have conceived of the soul as a sort of kinetic principle, if it be true that he said the loadstone has a soul because it moves iron. Diogenes, however, and certain others say that the soul is air, in the belief that it is the finest element and the ultimate principle. It is for this reason, also, that the soul knows and produces motion.

On the one hand, it knows by virtue of the fact that it is primary and other things are derivatives from it. On the other hand, it is the principle of motion by virtue of its being the first element. Heraclitus, also, says the soul is the first principle, since it is fiery vapor from which everything else is derived. It is also the most incorporeal of all the elements and is in constant flux. We apprehend that which is moved by what is in motion, and he believed, as did most others, that the real world is in motion. too, appears to have held views of the soul very similar to these. For he says the soul is immortal because it is like the Immortals, and this property of immortality belongs to it by virtue of its perpetual motion. Now, all divine things are in / perpetual motion, — moon, sun, stars, and all the heavens. Certain cruder thinkers, like Hippo, asserted that the soul is water. They appear to have based their belief on the nature of animal seed, which in all cases is moist. Hippo confutes those who say the soul is blood by the argument that the seed is not blood, and seed is the elemental soul. Others, like regard the blood as the soul, on the supposition that the most characteristic attribute of the soul is sense-perception, and sense-perception is due to the blood. So all the elements, with the exception of earth, have received a vote. No one has represented earth as the principle of soul, unless it were certain philosophers who regarded the soul as composed of all the elements, or as identical with them all. They all define the soul, one may say, in terms of three things: motion, sensation, and incor-l poreality, and each of these is referred back to ultimate elements. Therefore, with one those who define the soul in terms of knowledge, make it an element or a derivative of the elements. For they say that we know like by like, and inasmuch as it is the soul that knows all things, it must consist of all the elements. Those who maintain there is only one cause and one element, regard the soul as a unit, like fire or air. On the other hand, the philosophers who maintain that there are several elements, make the soul a plurality.

Anaxagoras alone declares that the soul is affected by nothing and has nothing in common with anything else. But, if this is its nature, he did not explain, nor is it evident from his writings, how the soul is to acquire knowledge and virtue. The philosophers who include contraries amongst their first regard the soul as composed of contraries. On the other hand, those who include in their principles only particular contraries, such as heat and cold or similar opposites, likewise regard the soul as one of these. And so there are some who take into consideration the derivation of the words, certain of them claiming that the soul is heat because the verb' to live' is derived from others claiming the soul is cold, because the name'soul' is derived from respiration and refrigeration. These, then, are the traditional views of the soul, and these are the grounds on which they have been advanced. We must now proceed at once to the investigation of motion. For the view that the soul is a self-moying entity, and capable of imparting motion, may not only be a false theory of its essence, but it may even be an impossibility for motion to inhere in it at all. We have already that what imparts motion is not of neces- /sity itself in motion. Everything that is moved is moved / in one of two ways: it is moved either by some other inasmuch as motion is employed in two senses, let us investigate the soul, and ask whether it is selfmoved or participates in movement. Movementsare of four kinds: movement in place, qualitative change, decay, and growth. The soul's movement, then, must be one, or several, or all of these. If it is not moved accidentally, its motion must be a natural attribute. If this is true, then space must be an attribute, for all of the aforesaid movements are spatial. If, then, the essential nature of the soul is self-movement, its movement will not be accidental,'as in the case of the movement of a white object or of an object three cubits long. For what moves is body, of which these are only predicates. Space, therefore, does not belong to them. But space is an attribute of the soul, if the soul by its own nature participates in motion.

Again, if the soul is moved by virtue of its own nature, it can also be moved by external force. And if it can be moved by external force, it can also be moved by virtue of its own nature. The same conditions hold in regard to rest; for in the state into which an object is moved by nature, in this state it also rests by nature. Likewise when an object is moved by external force into a certain state, it also rests in this state by force. It is not easy to give even a conjectural explanation of the character of forced states of motion and rest in the soul. Again, if the soul's movement be upward, its composition will be fire, and if downwards it will be earth, for these are the movements which are characteristic of these elements. The same reasoning holds good of the intermediate elements. Again, since the soul evidently sets the body in motion, it is reasonable that it also experiences those movements which it imparts. If this is true, it is also true conversely that the motion which the body < experiences is experienced by the soul. Now, the body is moved in space. The soul should therefore change place as the body does, and either the entire soul, or certain of its parts, should change position. If this is possible, then it would also be possible for the soul to enter again into the body after it had once passed out. From this would follow the impossible conclusion that animals once dead can rise again. In regard to movement in the sense of accident, the soul could be set in movement by some external body, for an animal might e.g. be pushed by external force. One must not, however, suppose that a thing which in its essential nature is self-moved, is moved by anything else save in an accidental sense; just as the absolute or final good cannot be the relative or secondary good. If the soul is moved at all, one would say that its motion is caused by the objects of sense more than by anything else.

However, if the soul moves itself, it must itself experience motion, so that on the supposition that every movement is the displacement of the object in motion, in so far as it is moved, the soul must suffer displacement out of its essential nature, provided its self-motion is not merely it is to its essential nature that motion belongs. There are also some who, like Democritus, and in a spirit similar to that of the comedian Philippus, say that the soul moves the (in which the soul resides), just as it moves itself. For Philippus tells us that Daedalus made his wooden statue of Aphrodite capable of movement by pouring quicksilver into it. And Democritus says much the same thing when he tells us that the spherical atoms, which are never at rest, move the whole body by their pull and push. But the question we have to ask is whether these same particles produce rest also. It is difficult or quite impossible to say how they are to do this. In a word, it is not in this way that. the soul seems to set the body in motion, but rather by some act of volition or thought. Similarly the explains on natural principles the soul's movement of the body: because it is selfmoved, it also moves the body with which it is intimately bound up. The Timaeus regards the soul as composed of the elements, and as divided into parts corresponding to harmonic numbers, in order that it may have an innate perception of harmony and possess in its entirety harmonic movements. Timaeus thus bent the straight line into a circle, which later he divided into two circles joined at two points, and further subdivided the original circles into seven others, on the supposition that the heavenly orbits correspond to the movements of the souly Against this view one may say, in the first place, that it is incorrect to speak of the soul as a, magnitude; by the soul of the universe he evidently means some such thing as what we call reason. At any rate it cannot, of course, be the sensitive or the appetitive soul, for their motion is not But reason is one and continuous, as is also the process of thought.

Now the process of thought consists of thoughts, and these in their succession form a numerical unity, though not a unity in the sense of magnitude. Neither is reason, therefore, continuous in this sense, but it is either indivisible or not continuous in the sense of magnitude. For how, indeed, is it to think, if it is magnitude? Does it think in its entirety or by means of some one of its parts? If it thinks by means of one of its parts, it must be either as a magnitude or as a point, if one can properly speak of a point being a part. Now, if it be as a point and the points are infinite in number, it is evident that it will never reach a conclusion; if, on the other hand, it be as a magnitude, it will think the same thing many times or an infinite number of times. But the fact seems to be that a thing is capable of being thought once for all. If, however, it is enough that the soul should have contact in any of its parts, why need it move in a circle or have any magnitude at all? But if thought requires contact in a complete circle, what is the significance of contact in any part? Again, how is the i8 soul to think the divisible by means of the indivisible, or that which has no parts by means of that which has parts? Eeason, however, must be a circle of this sort. For thought is the movement of reason just as revolution is the movement of a circle. If, then, thought is a revolving movement, reason must be a circle of which thought is the revolving movement. And, more than this, reason must always think something, if circular motion is perpetual. Now, this cannot be true, for the thoughts which issue in conduct have certain limitations (they are all determined by an end), and speculative | thoughts are determined by logical processes. Every logical process is either definition or demonstration. Demonstrations proceed from a premise and have some form of termination in a syllogism or conclusion.

And supposing they do not issue in a conclusion, still they do not turn back to the premise or starting-point, but continually take a new middle and extreme term, and so proceed in a straight line, whereas circular motion turns back to the starting-point. All definitions, too, are determinate. Further, if rotation completes itself several times, one will necessarily think the same thought several times. Again, thought seems more like rest and attention than like and the same thing applies to the syllogism. More than this, whatever is difficult or contrary to nature cannot be pleasurable. Now, if motion is not an essential property of the soul, the soul must move contrary to its nature. And it must be painful for it to be united with the body from which it cannot free itself, and such a union is even to be avoided, if it be true that the reason is better off when separated from the body — a view commonly held and concurred in by many persons. The cause, also, of the circular movement of the heavens is not clearly known. Circular movement is certainly not due to the essential nature of the soul, which moves in this way only accidentally, nor is it due to the body, for the motion of the latter is due to the soul. On the other hand, this motion is not ascribed to the soul because of its being a better form of motion, and yet it is just for this reason that God must have endowed the soul with circular movement, firstly, because itself in any body. This cannot be true, for every body appears to have a distinct form and character. Their doctrine is very much like saying that the art clothes itself in flutes, whereas an art employs its own instrument, just as a soul employs its own body. There is another theory of the soul handed down from our predecessors, which to the minds of many persons is no less convincing than the theories already described. Account has been taken of it even in our popular treatises. This theory regards the soul as a sort of Harmony, say its advocates, is a mixture and combination of opposites. The body, too, is composed of opposites.

Although it is true that harmony is a sort of relation in mixed parts or a combination of parts, we maintain that it is impossible for the soul fto be either of these. Again, although motion is not an attribute of harmony, yet almost all of the philosophers who hold the theory of harmony, I may say, ascribe motion to the soul. Another objection is that it is more fitting to apply the term harmony to conditions of health or to bodily qualities in general than to the soul. This becomes most evident when one attempts to describe the effects and functions of the soul in terms A HARMONY of harmony; for it is difficult to find any correspondence between them. Now, if we have two sorts of harmony in mind when we use this term, viz. harmony in the primary sense, which means such composition of magnitudes in objects possessing motion and position that they fuse together and admit nothing further that is homogeneous, and in the secondary sense, a ratio in mixed elements, — we still object that in neither sense does harmony apply to the soul. The composition of the parts of the body can be readily examined. There are manifold combinations of the parts, which may be effected in many ways. Of what parts, then, is reason a combination and how is the combination effected? And I raise the same question regarding the sensitive and appetitive soul. It is equally absurd to regard the soul as a ratio of mixture. The mixture of the elements, in the formation of flesh and bone, is not in the same ratio. If all the parts of the body are com-) posed of mixed elements, and the ratio of this mixture constitutes harmony and soul, we have the absurd result; that we possess many souls distributed through the entire body. One might demand from Empedocles an answer to this question, for he says that every one of these mixed elements is determined by a given Now the problem arises whether the soul is this ratio or is something else begotten in the members. Again, is Love the cause of any chance mixture or only of a mixture in which a fixed ratio is observed? And is Love this ratio or something transcending the ratio and different from it? This theory, then, involves such difficulties as the foregoing.

If the soul is different from the mixture or combination, why in the world is it that the soul is annihilated at the same moment as the existence of the flesh and the other parts of the living being? Furthermore, if each part does not have a soul, on the ground that the soul is not the ratio of mixture, what is it that is destroyed when the soul leaves the body? It is therefore clear from the fore going that one cannot regard the soul as a harmony/ or its motion as circular. It is, however, possible for it to be moved accidentally and to move itself, as e.g. that in which it is may be moved, and this in turn may be moved by the soul. But spatial movement is otherwise impossible for the soul. One might with better reason raise objections against the movement of the soul, by regarding the following facts. We speak of the soul as feeling pleasure, pain, courage, fear, and anger, and as perceiving and thinking. Now all these processes are apparently movements, and on this ground one might suppose that the soul is moved. This, however, is not necessarily so. For even if the feeling of pleasure or pain and the process of thinking be movements in the highest sense of the term, and each of these be a movement, it is possible that the movement is produced by the soul just as the feeling of anger or fear is effected by a given movement of the heart and thinking by a movement either of this or of some other sort. Further, some of these movements are local, others are processes of change, but of what particular sort or how effected must be considered elsewhere. However, to speak of the soul as feeling anger is like speaking of the soul as weaving, or building a house. It is better not to speak of the soul as feeling pity, or as learning or thinking, but rather of man doing this through the soul. We must not suppose, however, that this is so because there is movement in the soul, but that movement sometimes proceeds to the soul and sometimes it, as e.g. in sensation movement proceeds from outside objects, in recollection the movement is from the soul to excitations or fixed impressions lingering in the senseorgans.

Now, reason appears to be an entity which is implanted in the soul and is incapable of being destroyed; for if it were perishable it would be destroyed by the decay of old age more than by anything else. As a matter of fact, the case is the same as that of the sense-organs; for if the old man could have the eye of a young man he would see as well as the latter. Old' / age, then, does not come because the soul has some change, but the change is in the soul's organ, the body, as is the case in drunkenness and disease. Thought and contemplation are, it is true, weakened when some other internal organ is destroyed, but the principle itself is unaffected. The processes of discursive thought and the feeling of love or hate are not affections of the but of that which has reason in it, in so far as it has it. Therefore, when this organism is destroyed there is no longer either memory or love. For these are not affections of the reason, but of that union j of soul and body which has perished. Eeason, on the other hand, is something of a divine nature, and is' These processes are not aflfections of the eternal and separable Active Reason, but only of the body in so far as it possesses psychical life. unafifected by these changes. From these facts, therefore, it is clear that the soul is not in motion; but if it is not in motion at all, it is clear that it is not self-moved. By far the most unreasonable of the above-mentioned theories is the one which describes the soul as a selfmoving involving, as it does, impossibilities. In the first place, it involves impossibilities regarding its movement and especially regarding the notion of number. fl For how are we to conceive of a monad, a thing which is without parts and without differences, as in motion, and by what impulse and in what manner? If it imparts motion and is moved, it necessarily contains differences. Again, since it is said that a line in motion generates a plane and a point generates a line, then the movements of monads will be lines, for a point is a monad which has position. And the number of the soul is, of course, somewhere, and has position.

Again, if from a number one subtracts a number or a unit, the remainder will be a different number. But plants and many animals, when cut in two, live and appear to retain the same specific soul. It would also appear that there is no difference in speaking of monads and of small bodies. For if the atoms of Democritus are regarded as points, and quantity alone remains, there will still be in this quantitative element, as in everything continuous, a moving and a moved factor. And this consequence is due not to any difference inside, but merely to the fact that the elements are quantitative. There must, therefore, be something which sets the monads in motion. But if the soul is the cause of animal movement, it will also be the cause of movement in the number; the soul is therefore not at once the moving and the moved principle, but the moving principle alone. How then is it possible for the soul to be moved? There must be some difference between it and other monads. But what difference can there be in monadic points, excepting a difference in position? Therefore, even if the monads and points in bodies differ from each other, the monads will, nevertheless, be in the same space as the points. Eor the monad will occupy the space of a point. Now what is to prevent an infinite number from occupying the same space, if two can occupy the same space? This supposition, however, is absurd; for where the space occupied by bodies is indivisible, the bodies themselves are indivisible. But if the points in bodies are the number of the soul, or if the soul is the number generated out of corporeal points, why is it that not all bodies have a soul? For, presumably, there are points, — even an infinite number of points, — in all bodies.

Again, how is it possible for souls to be separated and disintegrated from if it be true that lines cannot be divided up into The peculiar absurdity of the number-theory consists, as we said above, on the one hand in the fact that those who advance it maintain the same position as the supporters of the theory that the soul is a subtle body; on the other hand, in their explaining the movement of the body by means of the soul after the manner of Democritus. For if there is a soul in every body capable of sensation, there must be, on the supposition that the soul is body, necessarily two bodies in the same space. Again, those who maintain the numerical of the soul become involved in the absurdity either that there are many points in a single point, or that every body has a soul, unless they make a distinction between physical and psychical points. The consequence is that the animal is moved by number, in the same way in which we said Democritus explained its For what is the difference whether we speak of the movement of small spherical bodies or of large monads or of monads at all? For in either case the animal movement must be due to the motion of the monads. The above objections and many similar ones may be raised against the third class of philosophers who combine motion and number in their theory. This is not merely an impossible definition of the soul; it is even an impossible attribute. This becomes evident if one tries to explain in terms of this the feelings and functions of the soul, such as deductions, sense-perceptions, pleasure and pain, and similar processes. It is not easy, as we said in terms of such a theory, to form even a conjecture of the nature of these functions. Of the three traditional explanations of the soul, there is one which describes the / soul as the most mobile element because of its selfmovement; there is another which describes it as the most subtle or incorporeal element. The difficulties and contradictions involved in these two have been pretty fully explained. There remains for us the consideration of the theory of its composition from the elements. The soul is composed of the elements, certain philosophers say, in order that it may perceive and know all reality.

But there are many difficulties which make this theory impossible. Its advocates assume that like is known by like, thus making the soul and its object in a sense identical. But the soul knows not merely these elements; it knows a great number, one would better say an infinite number, of other things, derivatives of the elements. Let it be granted that the soul knows and perceives the elements in every real thing; by what means is it to know or perceive the concrete object, e.g. what is God, or man, or flesh, or bone, or any other similar composite thing? For the elements are not combined in any haphazard way to form things, but in a fixed ratio and composition, as Empedocles himself says in regard to bone"Earth, the lovely, in her smelting pots, broad moulded. Obtained from sparkling Nestis two parts of the eight; Four from Vulcan's fire: so were white bones begotten." There is, therefore, no advantage in having the elements in the soul unless the ratios and combinations are also to be found in it. Each element will know its similar counterpart, but it will not know bone or man unless these also are to be found in it. One need scarcely say that this is impossible. For who could be in doubt whether a stone or man were to be found in the soul? The same holds true of the good and the notgood, and equally of other instances. Again, inasmuch as the term Being' is employed in several meanings (it denotes e.g. the individual concrete thing, or quantity, or quality, or some other particular category), the question arises whether the soul is composed of all these categories. It is supposed that there are no elements which are common to all the categories. Is the soul, then, lo composed only of the elements which fall under the category of substance? If so, how does it cognize the other elements? Are we to say that there are elements and specific principles which belong to every category of existence, and that the soul is composed of these? The soul will then be a quantity, a quality, and a substance. Now, it is impossible to form a substance or anything but a quantity out of elements of quantity. These and similar objections may be urged against the theory that u the soul is composed of all the elements.

Again, it is absurd to say that like is unaffected by like, and yet maintain that like perceives like, and that we know like by like. At the same time these writers regard perception, as well as thinking and knowing, as a sort of affection and movement. The theory, as states it, that things are severally cognized by means of somatic elements and that like elements are cognized by like, is open to many objections and difficulties, as is proven by what we have just said. For it is plain that such elements in animal bodies as are composed merely of gross matter, like bones, sinews, and hair, do not perceiveX anything, not even objects like themselves. According to the theory, however, they ought to perceive the like. Further, more ignorance than knowledge will attach to every element; for it will know only one particular thing, while it will be ignorant of much, for its ignorance will extend to everything else. And Empedocles is in the dilemma of making God the most unintelligent of beings; for he alone is ignorant of one of the elements, viz.. Strife, while mortals know them all, because they are formed from them all. There is, further, this generaj question to be raised: Why is it that all entities do not possess a soul, since everything is either an element or a derivative of one or several or all of the elements, and must, therefore, know one thing or certain things or all things? One might raise the further query: What is it that unifies these elements into objects? The elements are like a corporeal substrate, while it is the unifying | principle, whatever that may be, that is the main thing. But there can be no superior principle to dominate the soul. This impossibility applies most of all to reason. For reason is, with good cause, called nature's first-born ruler, although these philosophers regard the elements as the primary realities. All the philosophers who maintain the doctrine that the soul is composed of the elements because it knows and perceives realities, and those who describe it as the most mobile entity, fall into the error of not referring to the soul in its entirety. For not every sentient creature is capable of Certain aninlals are observed to be stationary in place.

And yet this seems to be the only form of movement that could be meant when one says' the soul moves the animal.' A similar objection may also be urged against those who describe the soul and the sentient principle as composed of the elements, viz., that plants evidently live without participation in movement or sensation, while many animals are not endowed with thought. But even if one were to make a concession and regard reason as a part of the soul, in a sense similar to that in which the perceptive faculties are parts of the soul, still even then one would not be taking every form of soul into consideration, nor the whole of any particular soul. And this is just what happens in the account of the soul given us in the Orphic verses, as we call For there we are told that the soul enters from the universe into individuals as they breathe, and that it is carried by the air. But this is impossible in the case of plants and also in the case of certain animals; because not all of" them breathe — a fact which the supporters of this view soul is homogeneous with its parts, if it be true that animals become endowed with soul by taking into themselves something from their environment. If, however, the diffused air is homogeneous, and the soul consists of heterogeneous parts, it is evident that some of its parts and not others will be contained in the air. The consequence is that the soul must either consist of like parts or not be found in every element of the universe. From the aforesaid it is evident that knowledge does not belong to the soul in virtue of its composition out of, the elements, neither is it right or true to say that it J is moved. But inasmuch as cognition, sense-perception, and opinion, as well as appetite, volition, and desire in general are functions of the soul, and inasmuch as locomotion in animals is effected by the soul, and it is also by virtue of the soul that animals grow, reach their prime, and decay, the question arises whether each of these functions is to be ascribed to the entire soul.

In other 4ii|/> words, is it by means of the entire soul that we think, perceive, and are moved, and perform and undergo every other process, or do we perform each different function by means of a different part? Again, we may ask whether the principle of life is found in each one of these parts or in several or in all of them. Or is something other than the soul the cause of life? It is true that some writers maintain the divisibility of the soul and that one part exercises thought and another part exercises desire. If the soul is really divided in its nature, what is it that holds it together? It is certainly not the body; for, on the contrary, one supposes that the soul holds the body together. At any rate, when the soul departs the body is dissolved and disintegrated. If, therefore, it is something other than the body that makes the soul an unit this would assuredly be the soul itself, and we shall be obliged to inquire again whether that unifying principle is itself an unit or is composed of several partsi If it is an unit, why should we not say at once that the soul is an unit? But if it is divisible, reason will again ask what that principle is which holds it together, and so the process will go on ad infinitum. In regard to the parts of the soul, one might inquire concerning the power which each of them has in the body. For if it is the soul as a whole that binds the entire body together, it would be fair to suppose that each part of the soul is the binding principle for some part of the body. This, however, appears to be impossible. It is hard even to fancy what sort of part the reason will bind or in what way. It is observed also that plants and certain insects, when divided, continue to live, because the sections possess souls, which are specifically, although not numerically, the same. Each part retains the power of sensation and locomotion for some time, and there is nothing strange in the fact that it does not continue to live, because it has no organ for the maintenance of its nature.

Nevertheless the parts of the soul are all found in every one of these bodily divisions, and they are of like kind with each other and with the entire soul; of like kind with each other because they are mutually inseparable; of like kind with the entire soul because it is divided into these as parts. Again, the fundamental principle of life in plants appears to be a kind of soul, and this is the only principle which animals and plants have in common. The principle of life can exist apart from sensation, but no sentient thing can exist without life.

Book 2

Let the foregoing suffice as a discussion of the traditional theories of the soul; and now let us resume our subject from the start, and attempt to determine the nature of the soul and its most general definition. One class of realities we call substance.' This'substance' may be regarded on the one hand as matter, which in itself is no definite thing; on the other hand,_as_form and idea, in terms of which definite individuality is ascribed to a thing. A third meaning of substance is the of matter and form. Matter is potentiality; form is actuality or The latter may be looked at' SUBSTANCE' in two ways, either as complete realization, — comparable with perfected knowledge, or as realization in process, — comparable with the activity of contemplation. The notion of substance appears to be most generally employed in the sense of body, and particularly of physical body; for this is the source of all other bodies. Some physical bodies have, and others have not, life. we under-, stand an inherent principle of nutrition, growth, and' decay. So that every natural body endowed with life would be substance, and substance in this composite sense. The body, therefore, would not be soul, since body is of such nature that life is an attribute of it. For body is not predicated of something else, but is rather itself substrate and matter. The soul must, then, be in this sense: it is the form of a natural body endowed with the capacity of life. In this meaning i substance is the completed realization. Soul, therefore,' will be the completed realization of a body such as) described. Complete realization is employed in two In the one sense it is comparable with perfected knowledge; in another, it is comparable with the active process of contemplation. It is evident that we mean by it here that realization which corresponds to perfected knowledge. Now, both waking and sleeping are included in the soul's existence: waking corresponds to active contemplation; sleep to attained and inactive knowledge. In a given case science is earlier in 6jthan observation. Sul, then, is the entelechy of a natural body endowed with the capacity of life. IX. Such a body one would describe as organic.

The parts of plants are also organs, although quite simple in character, e.g. the leaf is the covering of the pericarp, and the pericarp is covering of the fruit; the roots are analogous to mouths, both being channels of nutrition. If then we were obliged to give a general description applicable to all soul or life, we should say that it is the first entelechy of a natural organic body. It is therefore unnecessary to ask whether body and soul are one, as one should not ask whether the wax and the figure are one, or, in general, whether the matter of a particular thing and the thing composed of it are one. For although unity and being are predicated in several senses, their proper sense is that of perfect realization. We have now given a general definition of the soul, g We have defined it as an entity which realizes an idea. J It is the essential notion which we ascribe to a body of a given kind. As an illustration, suppose that an instrument, e.g. an axe, were a natural body. Here the notion of axe constitutes its essential nature or reality, and this would be its soul. Were this taken away it would no longer be an axe, except in the sense of a homonym. It is in reality, however, merely an axe, and of a body of this sort soul is not the notional tirst iu the sense of being nearest to mere potentiality, and in the order of development stands next above body. It is also first in being a prerequisite to all further development. The'first entelechy of a body' is, consequently, tbe first manifestation of life which an organism displays. It corresponds to dormant knowledge or merely possessed science, which is potentiality (Si/j/a/xts, compared with the active employment of science, and as potentiality, it is prior to the latter. I essence and the idea, but soul applies only to a natural body of a given kind, viz. a body whose principle of I movement and rest is in The principle expressed here should be observed in its application to particular parts of the body. For if the eye were an animal, vision would be its soul, i.e. vision is the notional essence of the eye.

The eye, however, is the matter of vision, and if the vision be wanting the eye is no longer an eye, save in the meaning of a homonym, as a stone eye or a painted eye. What applies here to a particular member, must also apply to the entire living body; for as the particular sensation is related to the particular organ of sense, so is the whole of sensation related to the entire sensitive organism, in so far as it has sensation.'Potentiality of life' does not refer to a thing which has become dispossessed of soul, but to that which possesses it. Seed and fruit are potentially living bodies. not but that there are certain other parts where nothing forbids their possible separation, because they are not realizations of any bodily And yet it is uncertain whether the soul as realization of the body is separable from it in a sense analogous to the separability of sailor and boat. Let this suffice as a definition and outline sketch of the soul. Inasmuch as the certain and the conceptually more knowable is derived from what is but sensibly more apparent, we must resume the investigation of the; soul from this standpoint. For it is necessary that the definition show not merely what a thing is, as most definitions do, but it must also contain and exhibit the cause of its being what it is. In reality, the terms of definitions are ordinarily stated in the form of conclusions. What, e.g. is the definition of squaring? The reply is that squaring is the conversion of a figure of unequal sides into a right-angled equilateral figure equal to the former. Such a definition is the expression of a conclusion. But to define squaring as the discovery of a mean proportional line is to define the thing in terms of its Eesuming our inquiry, we say, therefore, that the animate is distinguished from the inanimate by the principle of life. But inasmuch as life is predicated in several senses, e.g. in the sense of reason, sensation, local movement and rest, and furthermore movement in the sense of nutrition, decay, and growth if any one of these is discerned in a thing we say that it has life.

All plants, therefore, are supposed to have life; for evidently they have within them a potency and principle whereby they experience growth and decay in opposite processes. For their growth is not merely upwards or downwards, but in both these directions alike and in every point where nutrition takes place, and they continue to live as long as they are capable of nutrition. Now this faculty of nutrition is separable, from the other forms of life, but the other forms cannot] exist in perishable creatures apart from this principle of nutrition. This is made clear in the instance of plants; for they have no other capacity of soul (or life) (J than this nutritive one. Owing to this fundamental principle of nourishment, therefore, life is found in all animated living things, but the primary mark which distinguishes an animal from other forms of life is the possession of sensation. For even those creatures which are incapable of locomotion or change of place, but which possess sensation, are called animals and are not merely said to live. Touch is the primary form of sensation and is found in all animals. But as the nutritive faculty is separable from touch and sensation in general, so touch can exist apart from the other forms of sensation. By the nutritive power we understand that part of the soul in which plants share; and by the sensation of touch we mean that capacity which all animals possess. We shall later on give the explanation of these phenomena. For the present let it suffice that the soul is the causal principle of the aforesaid phenomena, and is defined in terms of them, mean, in terms of nutrition,' i sensation, reason, motion. To the question whether each of these forms of life is a soul or a part of the soul; and, if a part, whether in the sense that the part is only notionally separable or really separable in space, — the reply is in some respects easy and in others difficult. For in the case of plants, some of them appear to live when they are divided up and the parts are separated from each other, indicating that there is in each of these plants in actuality an unitary soul, but in potentiality several souls.

And we observe the same thing taking place in different varieties of soul, as e.g. in the case of insects which have been dismembered. Here each part is capable of sensation and locomotion, but if it is capable of sensation it is also capable of imagination and impulse. For where there is sensation, there is also pleasure and pain, and where there is pleasure and pain there is necessarily also desire. Now in regard to reason'iq and the speculative faculty, we have as yet no certain. evidence, but it seems to be a generically distinct type of' - — soul and it alone is capable of existing in a state of separation from the body, as the eternal is separable from the The remaining parts of the soul, however, n are from the foregoing considerations evidently not separable, as some But that they are notionally separable, is clear; for if perceiving is distinct from opining, the faculty of sensation or perception is distinct from that whereby we opine, and each of these is in turn distinct from the faculties above mentioned. Furthermore, all of these are found in some animals, while only certain of them are found in others, and in still others only a single one (and this is the cause of distinctions amongst animals). The reason for this must be investigated hereafter. A parallel instance is found in regard to sensation; some animals possess all the faculties of sense, others only certain of them, and still others only the single most fundamental one, viz. touch. The principle by which we live and have sensation, then, is employed in a twofold sense. Similarly, we employ the principle by which we know in a twofold sense, viz. science and the knowing mind (for we say we know by means of each of these), and in a like manner the principle by virtue of which we are healthy is in one sense health itself, and in another sense a part of the body or the whole of it. In these cases knowledge and health constitute the form, notion, idea, and, as it were, the realization of a potential subject, — the one of a knowing subject and the other of a healthy one, (realization is supposed to attach to that which has power to effect changes and is found in a passive and recipient subject).

The soul is that principle by which] in an ultimate sense we live and feel and think; so that it is a sort of idea and form, not matter and substrate. Now, substance is employed, as we have said, in a threefold meaning, viz. as form, as matter, and as a composite of these two. Amongst these meanings of substance matter signifies potentiality; form signifies actuality or, complete realization. Inasmuch as it is the composite which is the animate creature, body cannot be regarded as the complete realization of the soul, but the soul is the realization of a given body. The conjecture, therefore, i6 appears well founded that the soul does not exist apart from a body nor is it a particular body. The soul is not itself body, but it is a certain aspect of body, and is consequently found in a body, and furthermore in a body of such and such a kind. It is not to be regarded as it was amongst our predecessors who thought that it is introduced into body without prior determination of the particular sort of body, although no casual subject appears capable of undergoing any casual or haphazard This same result is also reached by an analysis of the notion itself; for complete realization in every instance is naturally found in a definite potentiality and in an appropriate matter. From this it is evident that the | soul is a kind of realization and expressed idea of a' determinate potentiality. In some creatures, as we have said, all of the above mentioned psychic powers are found, in others certain of them, and in still others only one. By powers we mean here the power of nutrition, of appetite, of sensation, of movement in space, and of rational thought. In plants, only the nutritive power is found; in other creatures the power of sensation is added. If sensation is added, impulse or appetite is also implied. For appetite includes desire and impulse and wish. All animals have at least one sense — touch; and to whatever creature sensation is given, to it are also given pleasure and pain, and objects appear to be pleasant or painful. Creatures which distinguish these, possess also desire; for desire is an impulse towards what is pleasant.

Further, animals possess a sense for food, and this is the sense of touch; for all animals are nourished by means J of the dry and moist, the warm and cold, and it is touch which apprehends these. It is only incidentally that animals discern food through other sensible qualities; neither sound nor colour nor smell contributes at all to food. Flavour, however, is one of the haptic Hunger and thirst are desires; hunger is a desire of the dry and warm; thirst a desire of the cool and moist, and flavour is a sort of seasoning in these objects. We must explain these subjects minutely hereafter; for the present let the statement suffice, that amongst animals where we find touch we find appetite also. The subject of imagination in animals is uncertain and must be investigated later. In addition to these attributes we find amongst some animals the power of local movement and in others we find the power of understanding and reason, as in man and in other creatures that are, if there be such, similar or superior to man. It is evident that a single definition can be applied to soul in the same way as a single definition can be applied to figure. As in the latter case, there is no figure beyond that of the triangle and its derivations, so in the former case there is no soul beyond those enumerated. A common definition might also be applied to figures which would fit them all and be peculiar to no particular figure. The same holds good in the case of the above mentioned types of soul. It is, therefore, both in these instances and in others, to search for a common definition which shall not apply to any individual real thing nor to any peculiar and irreducible species, thereby neglecting the particular meaning in the general. The facts touching the soul are parallel to this case of figure; for both in figures and in animate] creatures, the prior always exists potentially in the later,) e.g. the triangle is contained potentially in the square andf the nutritive power in that of sensation. We must, fore, investigate the nature of the soul in particular thingsy e.g. in a plant, a man, or a lower animal. And we must <! consider the cause of their order of succession.

The sensitive soul, for example, presupposes the nutritive, but in the case of plants the nutritive exists apart from the sensitive. Again, the sense of touch is presupposed by all the other senses, but touch exists apart from them and does not presuppose them. Many animals have no sense of sight, hearing, or smell. Some that are capable of sensation have also power of local movement, others have not; finally the smallest number possess the power of reason and understanding. Mortal creatures who possess the power of reason, possess all the other psychic faculties, but those which have each of these others do not all have the power of reason, and certain of them do not even possess imagination,'-'' while still others live by this alone. At another time we shall give an account of the speculative reason. It is evident, however, that this account touching each particular form of soul is also the most fitting description of the soul in general. If one intends to make an investigation of the faculties of the soul, it is necessary first to inquire into their several natures, and then by the same method to inquire further into other related problems. If, then, one is obliged to describe the nature of each several faculty, e.g. the nature of the faculty of reason, of sense-perception, or of nutrition, one must first be able to say what thinking and sense-perception mean. For the activities and processes are notionally prior to the faculties to which they belong. If this is true, we must further observe the objects of the activities before the activities themselves, and we should for the same reason first determine our position regarding these objects, e.g, regarding food, the sensible, and the intelligible. First, then, we must speak of food and generation. For the nutritive power is found in all living things, and is the primary and most universal faculty of soul, by virtue of which all creatures possess life. Its functions are to procreate, and to assimilate food.

In all animals that are perfect and not abnormal, or that are not spontaneously generated, it is the most natural function to beget another being similar to itself, an animal to beget another animal, a plant another plant, in order that they attain, as far as possible, the immortal and for this is what every creature aims at, and this is the final cause of every creature's natural life. We understand by final cause two things?l the purpose aimed at, and the person who is served by I the r Since it is impossible for an individual to partake of the immortal and divine in its own continuous life, because no perishable creature continues self-identical and numerically one, it partakes therefore of the immortal in that way in which it is able to share it, one thing in a higher degree and another in a lower; it does not itself abide, but only a similar self abides; in its continuity iF) is not numerically, but only specifically, one. The soul is the cause and principle of a living These terms are used in several senses. Corresponding to these differences, the soul is referred to as cause in three distinct meanings; for it is cause in the sense of the source of movement, of final cause, and as the real substance of animate That it is a cause in the sense of real substance is evident, for real substance is in every case the cause of being, and the being of animals is their life, and soul is the cause and principle of life. Furthermore, it is the complete realization that gives us the real significance of a potential being. Soul is also evidently cause in the sense of final cause. Jor nature, like reason, acts with purpose, and this purpose is its end. In animals the soul is, by virtue of its nature, a principle similar to this. For the soul uses all natural bodies as its instruments, the bodies of animals and the bodies of plants alike, which exist for the soul as their end. End is used in two senses: the purpose, and the person or thing which the purpose serves. Soul also means the primary source of local movement. This power of local movement is not possessed by all living creatures. Transformation and growth are also due to the soul.

For sense-perception is supposed to be a kind of transformation, and nothing is capable of sense-perception unless it has a soul. The case is similar with growth and decay. For nothing grows or decays by natural processes unless it admit of nutrition, and nothing is capable of nutrition unless it has a soul. Empedocles ascribes downward growth to plants where they are rooted, because the earth naturally tends downward, and upward growth, because fire tends in that direction, and in these respects is not right. For Empedocles does not employ the terms up' and' down' correctly.' Up' and down' are not the same for all things nor in all parts of the universe, for roots are to plants what the head is to animals,! if one is to describe organs as identical or different in terms of their functions. In addition, what principle is it that n holds together these two elements of fire and earth, tending, as they do, in opposite directions? For they will scatter asunder, if there be no hindering principle. And if there is such a principle, it is the soul and the cause of growth and nourishment. Some regard fire as the real cause of nutrition and growth. For this seems to be the only body or element that feeds and increases itself. One might, therefore, conjecture that this is the element that causes growth and nutrition in animals and plants. In a certain sense, it is true, fire is a cause, but not the absolute cause, of growth; this is ratherj the soul. For the growth of fire is indeterminate so long as there is material to burn; on the other hand, in all bodies developed in nature there is a limit and significance to size and growth. These attributes ([of limit significance]) belong to soul, not to fire, to reason rather than to matter. Since the same power of the soul is both nutritive and generative, we must first investigate nutrition; for it is by this function of nutrition that the faculty in question is distinguished from other faculties. Nutrition is supx5 posed to take place by the law of opposites, although not every opposite is nourished by every other, but such opposites only as derive both their origin and their growth from each Many things are derived from one another, but they are not all quantitative changes, as e.g. healthy from sickly.

Nutrition is not applied to these cases in the same sense, for while water is nutriment for fire, fire does not nourish water. The opposites of food and nourishment appear to apply particularly to simple bodies. There is, however, a difficulty here. For there are some who maintain that like is nourished by like, as like is also increased by like, while others, as we said, affirm the converse of this, viz., that opposites are nourished by opposites, on the ground that like is incapable of being affected by like. Food, however, undergoes transformation and is digested, and transformation is in every case toward the opposite or the intermediate. Further, food is affected by the body which assimilates it; the latter, however, is not affected by the food, just as the builder is not affected by his d material, although the material undergoes change through him. The builder merely passes from a state of inactivity into one of activity. The question whether nourishment is to be understood to apply to the final condition in which it is taken up by the body, or to its original condition, creates a difficulty. If both are meant, only in the one case the food is indigested and in the other digested, it would be possible to speak of nourishment conformably to both of the above theories; for in so far as it is indigested, we should have opposite nourished by opposite; in so far as it is digested, we should have like nourished by like; so that in a certain sense, it is evident they are both right and both wrong. Since nothing is nourished which does not share life, the object of nutrition would be an animate body as animate; so that food is determined by its relation to an animate object and is not accidental. There is a difference between the nourishment and the principle of growth; in so far as the animate thing is quantitative, the notion of growth applies; in so far as it is a particular substance, the notion of nourishment. For food preserves a being as a substantial thing, and it continues to exist so long as it is nourished. Nourishment is productive of generation, not the generation of the nourished thing, but of a being similar to it. For the former exists already as a reality, and nothing generates, but merely preserves, itself.

So then, such a principle of the soul as we have described is a power capable of preserving that in which this principle is found, in so far as it is found; nourishment equips it for action. When, therefore, it is deprived of nourishment, it can no longer exist. Since there are three distinct things here: the object nourished, the means of nourishment, and the power that causes nutrition, we shall say that it is the elemental soul that causes nutrition, the object nourished is the body which possesses this soul, and the means of nourishment is the food. And since it is fair to give everything a name in terms of its end, and since here the end of the soul is to generate a creature like to itself, the elemental soul might be called generative of that which is like to itself The means of nourishment is used in two senses, as is also the means of steering a ship; for one may refer to the hand, or to the rudder, the one being both actively moving and moved; the other only passively moved. All nutriment must be capable of being digested; heat is the element which accomplishes digestion. Everything animate, therefore, possesses heat. We have explained now, in outline, what nutriment is. The subject must be more minutely treated later on in its proper Now that we have arrived at the foregoing conclusions, let us discuss in general the entire question of senseperception. It consists, as we have said, in being moved and affected; for it is supposed to be a sort of internal transformation. Some maintain that like is affected by like. In what sense this is possible and in what sense impossible, I have explained in a general treatise On Activity and Passivity A difficulty is raised by the question why it is that perceptions do not arise from the senses themselves, and why it is that without external stimuli they produce no sensation, although fire and earth, and the other elements of which we have senseperception, are, either in their essential nature or in their attributes, found in the senses. It is, therefore, that the organ of sense-perception is not a thing in actuality but only in potentiality. It is consequently analogous to the combustible which does not itself ignite without something to set it ablaze.

Otherwise it would have burned itself and had no need of an active fire. Inasmuch as we say that perceiving used in two meanings (e.g. we call the capacity to hear and see, hearing and sight, although they may chance to be dormant, and we apply the same terms where the senses are actively exercised), so senseperception also would be used in two senses, the one potential and the other actual. First of all let us understand that the terms affection, motion, and activity, are used in the same meaning. For motion is a sort of activity, although incomplete, as we have said elsewhere/ Everything is affected and set in motion by an active agent and by something that exists in activity. Therefore in one sense a thing is affected by like, in another by unlike, as we have said; for it is the unlike that is affected, but after being affected it is like. We must, further, make a distinction touching potentiality and actuality, for we are now using these terms in a general sense. There is a sense in which we speak of a thing as knowing, as when we call man knowing, because man belongs to the class of creatures that know and are endowed with knowledge. There is another sense in which we speak of a man as possessing the particular knowledge of grammar. In each of these cases a man possesses knowledge potentially, but not in the same sense; the former is knowing as belonging to a certain genus and as having a native endowment; the latter is knowing in the sense of being able to exercise his knowledge at will, when nothing external prevents. In a still different sense there is the man who is actually exercising his knowledge, and is in a condition of complete realization, having in the strict sense knowledge of a particular thing, as e.g. A. The first two know in a potential sense; the one of them, however, knows when he is transformed through a discipline of knowledge, and has passed repeatedly out of an opposite condition; the other knows in the sense of possessing arithmetical or grammatical science and their passing from non-actual to actual knowledge is different.

Again, neither is the term passivity' used in an absolute meaning: in one meaning it is destruction by an opposite principle; in another meaning, it is the preservation of the potentially existent by means of the actual and similar, just as potentiality is related to actuality. That which possesses potential knowledge, for instance, comes to the actual use of it — a transition that we must either not call transformation (for the added element belongs to its own nature and tends to its own realization), or else we must call it a special kind of transformation. It is, therefore, incorrect to speak of thinking as a transformation when one thinks, just as the builder is not transformed when he is building a house. That which conduces to actualization out of a potential State in the matter of reasoning and thinking is not fairlycalled teaching, but must be given another name. Again, that which passes out of a potential state by learning or by acquiring knowledge at the hands of what actually knows and can teach, must either not be said to be affected as a passive subject, or we must admit two meanings of transformation, the one a change into a negative condition, and the other into a positive condition and the thing's natural The first in the sentient subject is wrought n by the generating parent, but after birth the creature comes into the possession of sense-perception as a species of knowledge. Active sensation is used in a way similar to active thinking. There is, however, this difference, that the objects which produce sensation are external,, e.g. the visible and the audible, and similarly other) sensible qualities. The reason for this is that active sense-perception refers to particular things, while scientific knowledge refers to the universal. These universals, how- / ever, are, in a certain sense, in the mind itself. Therei-' tore it is in one's power to think when one wills, but to experience sense-perception is not thus in one's power t for a sensible object must first be present. This also holds good of those sciences which deal with sensible realities, and for the same reason, viz. because these sensible realities belong to the world of particular and external phenomena. To go into the details of these questions would be more suitable at another time.

For the present so much may be regarded as fixed, viz. that the term potential' is not used in any absolute sense, but in one case its meaning is similar to our saying that a boy has in him the potentiality of a general, and in another case to our saying that a man in his prime has that potentiality — a distinction which also applies to the capacity for senseperception. Inasmuch as this distinction has no particular'8rt name in our language, although we have remarked that the things are different and how they differ, we must simply employ the terms affection and transformation as applicable here. That which is capable of sense-perception is, as we have said, potentially what the sensible is actually. It is, therefore, affected at a moment when it is unlike, but when it has been affected it becomes like and is as its In discussing any form of sense-perception we must begin with the sensible object. The object of sense' is used in three meanings, two of which touch the essential nature of sensation and one its accidents. Of the two first-named, one applies specially to each particular sense, the other is common to them all. By' object of sense' I mean a sense-quality _which cannot_be_apprehended by a sense different from that to which it belongs, and concerning which that sense cannot be deceived, e.g. colour is the peculiar object of vision,.souml of hearing, flavour of taste. however, discriminates several sense-qualities. The other particular senses, on the contrary, distinguish only their peculiar objects, and the senses are not deceived in the fact that a quality is colour or sound, although they may be deceived as to what or where the coloured or sonorous object may be. Such qualities are called the peculiar objects of particular senses, whereas common objects Touch distinguishes the properties of body as body, more specifically the qualities hard and soft, moist and dry, hot and cold, smooth and rough. Moreover, taste is, according to Aristotle, a kind of haptic function. motion, rest, number, form, magnitude. Properties _of the latter kind are not the peculiar objects of any but are common to them alL Motion is apprehended by touch and by sight. A thing is an object of sense accidentally, e.g. when a white object proves to be the son of Diares.

The latter is perceived accidentally, for the person whom one perceives is an accident of the white object. Therefore, the sense as such is not affected by the sensible object ([as a person]). To the objects of sense, strictly regarded, belong such properties as are peculiarly and properly sense-qualities, and it is with these that the essential nature of each sense is naturally concerned. The object of vision is the visible. The visible is colour and something whose notion is expressible, but for which there is no single definite What I mean will be best explained as we proceed. The visible, then, is colour, and this is diffused upon that which is in itself and by visible' in itself,' I do not mean notionally visible, but something which has in itself the cause of the visible. All colour has the power to move the actually diaphanous and herein consists its nature. Therefore colour is not visible without light, but every particular colour is seen in the light. For this reason we must first explain what light is. Light is something diaphanous. By diaphanous I mean that which is visible, though not in itself and absolutely, but only by means of an agent, namely colour. Of such nature is air and water and many other bodies. Water and air are not diaphanous as water and air, but because there is in both these elements the same property that is found in the eternal empyrean. The activity of this diaphanous, as such, is light. But where the diaphanous exists only potentially, there is darkness. Light is the colour, as it were, of the diaphanous, when the diaphanous is made really so by fire or by some such agent as the supernal body, for in the supernal body there is something which is identical with fire. The nature of the diaphanous, therefore, and of light has been explained. Light is, namely, neither fire nor in a word any body nor the efflux of any (for this would then also be a body), but it is the presence of fire or some such agent in a diaphanous medium. For two bodies cannot occupy the same place at the same time. Light appears to be the opposite of darkness.

Darkness is the privation of a condition of the diaphanous, the presence of which condition is light. is wrong, as is every one else who has held a like theory, in thinking that light moves itself and at some time or other projected itself into the interval between the earth and the surrounding space, without our being conscious of it. For this is contrary to plain reason and to observed facts. In a small space, the fact might escape us, but in an interval that extends from east to west, to claim that the fact escapes our notice is asking too much. It is the colourless that is receptive of colour, and the nonsonorous that is capable of sound. Colourless are the diaphanous and the invisible, or that which is scarcely visible, as for example, the dark. Of such nature is the diaphanous, but only when it is so potentially and not actually. For the same medium is sometimes dark and sometimes light. Not all objects are visible in the light, but only the peculiar colour of each object. For certain objects are not visible in the light, but stimulate sensation in the as e.g. those fiery, shining phenomena that have no class-designation such as mushrooms, horn, and the heads, scales, and eyes of fish, while the peculiar colour of none of these objects is seen. The explanation of their visibility is subject for a different treatise than the present. So much is now clear: it is colour that is visible in light. Therefore without light colour is not visible. For it is the essence of colour to set the actually diaphanous in motion, and the diaphanous in actuality is light. Clear evidence of this is the fact that if one places a coloured object on the eye, it is not seen. On the contrary, it is the diaphanous, as e.g. the air, which is stimulated by colour, and the sense organ is stimulated by this contiguous medium. Democritus is wrong, then, in supposing that if the medium were a vacuum our vision would be accurate, even to the seeing of an ant in the sky. This is impossible, for vision takes place from the fact that the percipient organ undergoes n an effect, and this effect cannot be produced directly by the visible colour.

So that there remains only the supposition that it is produced by a medium, and consequently there must be a medium. And were a vacuum produced, there would not only be no accurate vision, but no vision at The reason why colour is visible only in the light has been explained. Fire, however, is visible in both light and darkness, and necessarily so, for it is by the agency of fire that the diaphanous becomes diaphanous. The same statement applies also to sound and smell. For nothing when placed in actual contact with the senseorgan produces the sensation of sound or smell, but by means of odour and sound a medium is set in motion and through this the sense organ in each case is affected. But if one should place a sonorous or odorous object on the sense organ itself, no sensation would be produced. In the case of touch and taste, similar conditions hold good, although not apparently. The reason for this will be evident later. The medium for sound is the atmosphere; the medium for smell has no name. It i& an element that is common to air and water, and as the diaphanous is related to colour, so there is a something in water and air similarly related to an odorous body. For aquatic animals appear to be capable of the Let us now first of all discuss the subject of sound and hearing. Sound is twofold. It is one thing in actuality,, j and another in potentiality. Some things, we say, are incapable of sound, such as a sponge or wool, others are resonant, such as bronze and bodies that are hard and smooth, because they can emit sound; that is, they have the power to create an actual sound through mediation between the resonant object and the hearing. The actual sound is always produced by something in reference to something and in a A blow is the producing cause. It is, therefore, impossible for an object, taken alone, to produce a sound, for the striking agent and the struck object are different. Thus the sonorous body produces sound by its relation to another body. A blow is impossible without movement, and, as we have said, sound does not result from a blow upon any haphazard object. Wool, e.g. when struck produces no sound, but bronze and whatever is hard and smooth do.

Bronze is resonant because it is smooth. Hollow bodies, by reverberation, produce many reports after the first one, because the air, when it is once set in motion, can find no egress. Furthermore, audition takes place in air and water, but to a less degree in the latter. But neither air nor water is the main thing in the case of sound. The percussion of solid bodies against each other and against the air must take place, and this takes place when the smitten air resists and is not dissipated. Therefore if it is struck quickly and violently it produces sound, for the motion of the striking agent must anticipate the dispersion of the air, as if one were to strike a pile or rapidly shifting chain of sand. An echo is produced when from the air which is made unitary by means of the vessel that confines it and keeps it from dispersion, an oncoming mass of air is driven back again, like a rebounding An echo is for the same conditions hold good of both sound and light. Light is constantly reflected (otherwise light would not be found everywhere, but there would be darkness outside the region illuminated by the sun), but the reflection is not similar to that which is caused by water or bronze or any other polished solid, where a shadow is cast whereby the light-area is delimited. A void is correctly regarded as a chief factor in hearing. Now, the air appears to be a void, and this, when it is moved as a single and continuous element, is what produces hearing. But, because of the swift dissipation of the air, no sound arises unless the object struck be smooth. In this case, however, the air by reason of o' the even surface, is made one throughout, for the surface of a smooth body is one throughout. A body is sonorous when it is capable of setting in motion up to the organ of hearing the single and continuous air. Hearing is naturally related to the air, and owing to the fact that sound is in the air, the inner air is set in motion by the moving outside air. Therefore, an animal does not hear in all parts of its body, neither does the air penetrate everywhere.

And the psychical organ that is to be stimulated does not contain air in all its parts. The air in and for itself is, by reason of its facile dispersion, non-sonorous. But when it is restrained from dispersion, its motion produces sound. The air within the ears is so deeply immured as to be in itself immovable, in order that it may detect all distinctions in communicated motions. For these reasons we hear in water, because the water has no access to the congenital air, nor does it penetrate even into the ear because of the latter's convolutions. When, however, this does happen, hearing ceases. Neither do we hear when the membrane is diseased, just as the eye has no vision when its cornea is diseased. A test as to whether hearing is intact or not is found in the ears' continually resounding like a horn. The air in the ear has its own peculiar motion, although sound is foreign to this internal air and is not one of its properties. It is for this reason that we speak of hearing by means of a void and resonant organ, because we hear by means of something which contains confined air. The question arises whether it is the striking agent or the object struck that produces sound. Or is it both of these, but each in a different sense? Sound is a sort of motion of an object which is capable of being moved in the same way as the particles that rebound from smooth surfaces when one strikes them. Not every object, as has been said, produces sound when struck or when striking another object, as e.g. in the case of one sharp point striking another. On the contrary, the object that is struck must be smooth, so that the air may be thrown off and agitated in a mass. Distinctions in resonant bodies are discernible in the actual sound they produce. As without light no colours are visible, so without sound the acute and grave are not discernible. These terms are employed metaphorically and are drawn from the tactual sense. The acute stimulates sensation quickly and strongly, and the grave slowly and in a small degree.

It is not the however, that is quick nor the grave that is slow, but merely the motion of the one is called quick by reason of its swift action on the sense, and the other is called slow by reason of its tardy action. The analogy appears to apply to acute and dull in the sense of touch. The acute e.g. pricks and the blunt pushes, as it were, because the motion of the one is quick and of the other slow, so that the effect of the one takes place swiftly and of the other tardily. Let so much suffice for the discussion of sound. Voice is the sound produced by a living being. No inanimate thing has voice, unless one speaks metaphorically, as e.g. the flute, lyre, and other inanimate instruments are said to have a certain range, melody, and expression, properties which are possessed also by the voice. Many animals are without voice, as the bloodless animals, and, amongst the sanguineous, fishes. This has its good reason, seeing that sound is a movement of the air. Fishes that are said to have voice, such as those in the produce a sound by means of their gills or some such organ. Voice is the sound made by a living creature, and made not by any accidental organ. But since nothing emits sound unless there is a striking agent, a thing struck, and a medium, viz. air, it would be reasonable to suppose that only those animals that breathe air possess voice. Now nature employs respiration for two purposes, just as she employs the tongue both for the function of taste and of speech, of which functions taste is necessary (and therefore is found in all animals generally), whereas the communication of thought is given for the ends of higher living. So it is with respiration, which performs a function in reference to the internal warmth, and as such is necessary for living (the reason will be explained elsewhere), and another function in reference to speech, where it subserves the ends of higher living. The windpipe is the' organ of respiration, and this organ in turn subserves another, the lungs, and it is in virtue of the latter that land animals have more heat than others. The pericardiac region first of all needs and, therefore, it is essential that the air be inspired inwards.

And so it is the percussion of the inspired air, directed by the soul in those inward parts, against the windpipe, i8 as it is called, that constitutes voice. Not every sound of an animal is voice, as we have said (for it is possible to make noises with the tongue or such as people make in coughing), but the impact of the air must be animate and combined with some idea in order to be called voice. For voice is significant sound and not merely the sound of respired air, as is the case in coughing. On the contrary, the animal by means of this respired air produces an impact of the air already in the windpipe against the trachea itself. This is proven by the impossibility of vocal utterance when we neither inhale nor exhale but simply hold our breath, because in holding the breath we thereby disturb this vocal process. Also, we see from this why it is that the fishes have no voice, being, as they are, without a windpipe. They lack this organ, because they are incapable of inhaling or exhaling air. The explanation of this is matter for a different treatise. Smell and its object are less easy to define than the foregoing senses, for the nature of smell is not so clear to us as is that of sound and colour. The reason for this is the fact that this sense with us is inaccurate and less perfect than in many animals. Man has a poor sense of smell, and smells no odorous object without painful or pleasant association, because the sense-organ does not sharply discriminate qualities. It is probable that the hard-eyed animals discriminate colours in the same way, and that distinctions in colour are not clear to them except as they have the feeling of fear or not. So it is with smell in the human race. Smell has apparently some analogy to taste, and the species of flavours correspond to those of odours; but our sense of taste is more accurate because it is a sort of touch, and the sense of touch is the most accurately developed of all the senses in man. In the case of the other senses, man is inferior to many animals, but in discriminations of touch he is far superior to the others. For this reason man is the most intelligent animal.

A proof of this is the fact that within the human race the good or bad native endowii.,. Such animals have no eyelids, as e.g. crabs. ment of individuals depends upon this sense organ, and no other. Men who have hard flesh are poorly endowed intellectually, men who have soft flesh are As one flavour is sweet, another bitter, so it is with smells. Although in some cases smell and flavour correspond to each other, — I mean, for example, where we have a sweet smell and a sweet flavour, — in other cases they are contraries. In like manner we refer the qualities of pungent, harsh, piquant, and oily to smells as well as to flavours, but, as we have said, owing to the fact that smells are not so clearly discriminated as flavours, these terms are borrowed from taste on account of similarity in the sense objects. For the smell of saffron and honey is sweet, and the smell of thyme and similar herbs is pungent. The same holds good of other qualities. Further, just as hearing and each particular sense distinguishes its own object, in the one case the audible and inaudible, in another case the visible and invisible, so also smell distinguishes the odorous and inodorous. And the inodorous is so called, in one case, from the fact that it is totally incapable of yielding smell; in another case because the smell is faint or indefinite. Similarly one employs the term insipid. Smell is transmitted through a medium, such as air or water. For aquatic animals appear to smell; so, too, sanguineous and bloodless animals, and the birds of the air, have this sense. Some of the latter are endowed with the power of scent and mark their prey from afar. It seems doubtful, therefore, whether the process of smell in all these animals is alike. Man smells while inhaling, but without inhaling and while exhaling or holding his breath, he does not smell, whether the object be remote or near, not even if it be placed in the nose itself. That an object when placed upon the sense-organ itself is not perceived, is a fact common to all the animals. But not to perceive odours without inhaling is peculiar to man, as may be proven by experiment.

Were it not so, the bloodless animals, inasmuch as they have no respiration, would have to possess a sense beyond those already named. But this is impossible, if it is true that they perceive smells, for the perception of the odorous, whether pleasant or unpleasant, is the sense of smell. Furthermore, as these animals appear to be destroyed by strong fumes, just as man e.g. is destroyed by pitch, sulphur, and similar fumes, they must have the sense of smell, although they do not respire. The organ of smell in man appears to differ from that in the other animals, just as his eyes differ from those of the hard-eyed animals. For the eyes in man have a protection and, as it were, a sheath in the eyelids, and without moving or opening these he does not see. Whereas the hardeyed animals have no such protection, but see at once whatever comes into the field of vision. So also the organ of smell in some animals is uncovered, as the eye is; while in others that respire, it has a covering, which opens in inspiration and by the dilation of veins and pores. For this reason the animals that breathe do not smell in water. For in order to smell they must inhale, and in water this is impossible. Smell is a property of the dry, as flavour is of the moist, and the organ of smell is potentially analogous to its object. The sapid is a tactual property, and this explains the fact that it is not perceived through the medium of any foreign For neither is the tactual so perceived. The body in which flavour, i.e. the gustable, is found consists in something moist as its matter, and this moist element is something tangible. Consequently, if we were in the water and something sweet were thrown into it, we should perceive it. The sensation, however, would not have been produced in us through a medium, but by the mingling of the sweet with the moist, as is the case with a beverage. Colour, on the other hand, is not perceived by means of its being mingled with anything, nor by means of emanations. There is in the case of taste no medium; in other respects, however, as colour is to the visible, so is taste to the sapid.

Nothing can stimulate the sensation of flavour apart from the moist, but an object must possess moisture either actually or potentially, as does salt. For salt is easily soluble, and melts on the tongue. As sight is discriminative of the visible and invisible (for darkness is the invisible, and on this, too, sight exercises judgment), further of the extremely dazzling (for this is also invisible, but in a different sense from darkness), so, too, hearing is discriminative of sound and silence, of which the one is audible and the other inaudible, and of the crashing sound, as sight is discriminative of dazzling brightness (for as a tiny sound is inaudible, in a certain sense a great and crashing sound is also inaudible). The term invisible is used, on the one hand, in an absolute sense, and means the same as the term impossible does in other cases; on the other hand, it is used in the sense of what is naturally meant to be seen, but is not seen, or only imperfectly seen, just as one applies the terms footless and seedless to animals and fruits that are imperfect. So also is taste discriminative of the gustable and non-gustable; the latter is that which has an insignificant or indistinct flavour, or a flavour that is subversive of taste. The potable and non-potable seem to be the final principles of taste; taste implies both of them. The one is, however, indistinct or destructive of taste, while the other is natural to the sense. The potable is common to the senses of touch and taste. Since the sapid is moist, it is necessary that the sense-organ be neither actually moist nor incapable of becoming moist. For taste is affected by the sapid object as sapid. Consequently it is necessary for the organ of taste to be capable of becoming moist, without injury and without becoming intrinsically A proof is the fact that the tongue, when it is very moist or very dry, is incapable of perceiving the sapid. For in this case there arises merely a tactual impression of the simple liquid, just as when one first tastes a strong flavour and then essays another, or as everything seems bitter to an invalid because his tongue is full of this bitter moisture.

The varieties of flavours, as in the case of colours, are partly simple opposites such as sweet and bitter, partly the affiliated qualities oily and salty, and the intermediate qualities of pungent, harsh, astringent, and acid. For these seem to include approximately all the distinctions in So then the sapid sense is potentially of the same character as the sapid object which actually produces the sensation of taste. The same kind of reasoning applies to the tangible and the sense of touch. If touch is not a single sense but several, then tangible objects must also be manifold. There is some doubt whether touch is manifold or unitary, and it is uncertain what the sense-organ is which apprehends the tangible. Is it the flesh in man, and in other animals something analogous to flesh, or is the flesh only the medium, while the primary organ is something different and internal? Every sense appears to apprehend only one contrary, e.g. sight senses black and white; hearing, acute and grave; taste, bitter and sweet. In touch, however, are found many opposites: hot and cold, moist and dry, hard and soft, and other similar opposites. There appears, however, to be a solution for this difficulty in the fact that several opposites apply to the other senses also, as e.g. in sound there are not only the properties acute and grave, but also large and small, and smooth and hard, and similar qualities are applied to the voice. Similarly, different distinctions are applied to colour. But what forms the single substrate for touch, as sound does for hearing, is not clear. Another question is whether the sense-organ is internal or not, or whether the flesh immediately senses touchqualities. The fact that sensation is simultaneous with contact is no proof here. For as a matter of fact, if one should prepare a membrane, as it were, and draw it over the flesh, one would still have the sensation of touch at the moment of contact, and yet it is plain that the senseorgan is not in the membrane. Even were it grown together with the flesh, the sensation would only the more quickly penetrate it. Consequently this part of the body seems to be related to us as the air would be, were it grown to us round about.

For we should then have to perceive sound, colour, and smell in each instance by means of a single sense-organ, and sight, hearing, and smelling would in that case have become a single sense. However, as a matter of fact, since the media through which sense-movements are transmitted are different, the sense-organs themselves are different. In the case of touch this is not clear; for it is not possible that a living body should consist of air or water; it must be a solid body. It remains that it is a body composed of earth and those two former elements, air and water, in such way as it is intended flesh and what is analogous thereto should be. Consequently, the body ([i.e. the flesh]) must be the natural medium for the sense of touch, by which the several sensations are mediated. That they are several is evident from the character of touch on the surface of the tongue. For the tongue, as a single organ, discerns all tactual and sapid qualities. Further, if the rest of our flesh were to discern sapid qualities, touch and taste would be regarded as one and the same sense. But as a matter of fact they are regarded as two, because they are not convertible. Since body has depth, i.e. the third dimension, wherever there is an intermediate body between two other bodies the question might be raised whether it is possible for these two bodies to be in contact with each other. Now, neither the moist nor the fluid is incorporeal, but each must necessarily be water or contain water. But objects which are in contact with each other in the water, inasmuch as their extremities are not dry, must have water between them, in which their outer circumferences are submerged. Now, if this is true, it is impossible for two objects in water to be in contact with each other. The same holds good of the air (for air is conditioned in the same way towards the objects in it as water is towards objects in water, only in the former case the conditions are more elusive for us ([who live in an atmospheric medium]), just as aquatic animals fail to observe that the fluid is in immediate contact with the fluid.

A further question then arises, whether the same process of sensation applies to all senses alike, or whether in different senses the process is different, just as touch or taste was seen to function by means of immediate contact, while the other senses function from a distance. This last distinction is not real, but both the hard and soft we perceive through media, as we do also the sonorous, the visible, and the odorous; in the one case we have objects at a distance, in the other, close at hand. This is the reason why the medium eludes our observation. For we do sense everything through a medium, but in the case of things close at hand, the BK.. existence of the medium escapes us. And yet, as we said above, were we to perceive all tangible qualities through the medium of a membrane without knowing that a medium intervened, we should then be in the same condition as we now are in the media of air and water. For we appear now to be in contact with things themselves, and not to apprehend them through a medium. The tangible, however, differs from the visible and audible in that we perceive the latter by the medium producing a certain effect on us, while qualities of touch we do not perceive by means of the medium but simultaneously with it, as a man who is struck through his shield. For the struck shield does not strike him, but rather shield and man are simultaneously struck. In a word, flesh and the tongue seem to be related to the sense-organ as air and water are severally related to sight, hearing, and smell. For were the sense-organ itself brought into contact with the object, sensation would not result either in the one case or the other, just as little as vision would result were one to lay a white object on the surface of the eye. By which it is evident that the organ of touch must be for in this way it would be parallel with the other senses. When objects are placed upon the sense-organ, sensation does not result; on the other hand, when placed upon the flesh, sensation does result. Flesh must, therefore, be merely the medium of touch. The distinctions of body as body are tactual.

By distinctions I mean such as characterize the elements — viz. warm and cold, dry and moist, concerning which we have spoken in an earlier treatise On the elements The senseorgan which perceives these distinctions is touch, and the part in which the sense of touch, as we call it, is primarily found is potentially what tangible objects are actually. For sensation means being affected in a certain way; so that whatever makes another thing to be in reality like itself does so by virtue of that thing's having this nature in potentiality. Therefore we do not perceive hot and cold, hard and soft, in objects that have these qualities in like degree as ourselves, but we perceive the excesses, as if sense were a sort of mean between opposed sensible objects. And hence it discriminates sensible objects. The mean is capable of judgment, for it becomes in reference to each of the extremes another extreme. And as that which is to perceive white or black must not itself be actually white or black, but both of these potentially (and the same holds good of other instances), so also in the case of touch, it must not be either hot or cold in itself. Furthermore, as sight was said to discriminate in a sense both the visible and invisible, and the other senses in like manner their opposites, so also touch discriminates the tangible and intangible. And by intangible I mean those things where tactual discriminations are quite indistinct, as e.g. in the case of air, and those excesses of touch that are destructive of the sense. Each of the senses has now been treated in outline. In reference to sensation in general we must understand that a sense is capable of receiving into itself sensible j forms without their matter, just as wax receives into itself the mark of a ring without its iron or, gold; — it receives into itself a gold or bronze pression, but not as gold or bronze. In like manner also sense is impressed by every object that possesses colour or flavour or sound, not in so far as each of these objects bears a given name, but in so far as it has such and such a quality and expresses an idea. The organ of sense is fundamentally that in which this power of being impressed exists.

It has therefore an identity with the object that makes the impression, but in its mode of expression it is different. Otherwise that which perceives would be a sort of magnitude; whereas the mode of expression of the perceptive faculty and of sensation is not magnitude, but only a certain relation and potentiality of magnitude. From this it is clear why excesses in sensible objects destroy the sense-organs. For if the stimulus be stronger than the organ, then the relation between them is destroyed, just as harmony and tone are destroyed when the strings are struck too C/Zy violently. Why is it, then, that plants have no sensation, having as they do a certain psychical endowment, and being affected by tangible qualities, for they experience e.g. cold and heat? The reason is that they have no mean in their nature, nor such a principle as is capable of receiving into itself the forms of sensible objects; on the contrary they are affected materially. One might raise! the question whether a thing which cannot smell can be affected by odour, or that which cannot see can be affected by colour, and so on. Supposing that the object of smell is odour, odour produces the sensation of smell, if it produces anything at all; so that nothing which is | incapable of smelling can be affected by odour. The same reasoning applies to the other senses. Neither can) sentient beings be affected further than they are in each j case sentient. This is also evident from the following: neither light nor darkness, sound nor smell, acts upon bodies, but the media in which these qualities exist may act upon bodies, e.g. it is the air which is combined with thunder that rives the tree. Tangible qualities, however, and flavours operate directly. If this were not so, how could inanimate bodies be affected and changed? Do the other qualities then act directly also? Or is it rather true that not every body is capable of being affected by smell and sound, and those which are so affected are indefinite and unstable, as e.g. the air? For air emits odour as if it were affected by something. What is smelling, then, beyond this being affected by something? Smelling surely means also perceiving, whereas the air by being affected is only made the ready object of perception.

Book 3

That there is no additional sense beyond the five we have enumerated (I mean sight, hearing, smell, taste, and touch), one may believe from the following considerations. Granted that we really have perception of everything for which touch is the appropriate sense (for all the qualities of the tangible as such are apprehended by touch), it is necessary that if any sensation is lacking, some organ must also be lacking in us. Whatever we perceive by contact is perceived by the sense of touch, with which we are endowed. On the other hand, whatever we perceive through media and not by direct contact, is perceived by simple elements, such as air and water. The conditions here are such that if several sensible objects which differ from each other generically are perceived by a single medium, then anyone who has a sense-organ analogous to this medium must be capable of perceiving these several sense-objects. For example, if the sense-organ is composed of air and the air is the medium of both sound and colour, the organ would perceive both these sense-qualities. If, on the other hand, several elements are mediators of the same sense-qualities, as e.g. colour is mediated both by air and water (for both are diaphanous), then the orgari which contains one of these elements alone will perceive that which is mediated by both of them. The sense-organs are composed exclusively of these two simple elements, air and water (for the pupil of the eye is composed of water, the hearing of air, smell of one or the other of these). Fire, however, belongs to no organ or it is common to them all (for nothing is sentient without heat). Earth belongs either to no organ or it is chiefly and in a special manner combined with touch. Nothing would remain, therefore, excepting air and water, to constitute a sense-organ. Some animals have, in actual fact, these orgahs as described. Animals which are perfect and not defective have all these senses. For even the mole, as one may observe, has eyes underneath its skin.

Consequently, unless there are bodies other than those known to us, or qualities other than those which belong to earthly bodies, we may conclude there is no sense lacking in Neither is it possible that there should be any peculiar organ for the perception of common properties such as we perceive by means of the individual' senses, e.g. common properties like motion, rest, form, magnitude, number, unity. For all these properties we perceive by means of motion, e.g. magnitude is perceived by motion. So also is form, for form is a sort of magnitude, and rest we perceive from the absence of motion. We perceive numbers by the negation of continuity and by the special senses, for each sensation is experienced as a unit. So, then, it is clearly impossible that any particular sense should apply to these common properties, such as motion. For this would be like one now perceiving the sweet by means of sight. This is s because we happen to have senses for both qualities (i.e. for the sweet and for colour]), whereby when the given qualities coincide in one object, we recognize the object as Otherwise we do not perceive the sweet, excepting in the sense of accident, as e.g. when we recognize the son of Cleon not because he is Cleon's son, but because he is a fair object, which for the son of Cleon is an accident. We have indeed a'common sense' for the perception of common qualities. I do not mean accidentally. It is therefore not a particular sense, for in that case we should perceive in no other way than as just now described in the illustration of Cleon. A sense, however, perceives accidentally the qualities that are peculiar to a different sense, not in their own nature but because of the unity of these qualities, as when two sense-qualities apply to the same object, e,g. in the case of bile that it is both bitter and yellow. Now, it is not the function of either particular sense to say that both these qualities inhere in one thing and it is owing to this fact that error arises, when in the case of a yellow substance one opines it to be bile. One might ask why we are endowed with several senses and not with one only.

Is it not that facts of sequence and coincidence, such as motion, magnitude, and number, might the less escape us? For if we possessed sight only, and this were limited to the perception of whiteness, then all other distinctions would the more easily escape our knowledge, and because colour and magnitude are always coincident, they would appear to be identical. In point of fact, however, since these common qualities are found in different sense-objects, it is evident that the several qualities themselves are different. i(. But inasmuch as we perceive that we see and hear, we must have this consciousness of vision either by the instrument of sight or by some other The same faculty will then apply both to sight and to colour, the object of sight. In this case, either we shall have two senses for the same thing, or a sense will be conscious of itself. Further, if there is another sense for the perception of sight, either we shall have an infinite regressus, or a given sense must finally be cognizant of itself, in which case one would better admit this in the instance of the original sense itself, i.e. sight. Here, however, is a difiiculty. For, if sensation by means of sight is vision, and colour or that which possesses colour is what we see, then the seeing faculty itself must first of all have colour in order to be seen. It is plain, therefore, that sensation by means of sight is not employed in a single meaning. For even when we do not see, it is by means of sight that we judge both of darkness and light, although not in the same way. Furthermore, the seeing subject is in a certain sense saturated with colour, since each sentient organ receives into itself the sensible object without its matter. This explains the fact that when objects sense have been removed, the sensations and images sti persist in the sense-organ. The actualization of the object of sense and of the sense itself is one and the same process; they are not, however, identical with each other in their essential I mean, for instance, actual sound and actual hearing are not the same. For it is possible for one who has hearing not to hear, and for a sonorous body not to emit sound at every instant.

When, however, that which has the potentiality of hearing and that which has the potentiality of sounding, actually hear! and actually emit sound, at that moment the realized hearing and the realized sound are simultaneously complete, and one would call them respectively the sensation of hearing and the act of sounding. If, then, movement, activity, and passivity are implied itf the produced object, it must be that actual sound and hearing exist in a potential state. For creative and motive activity is given in antecedent It is, therefore, not necessary for the moving principle to be itself in actual motion. For as action and passion find their expression in the object acted upon and not in the producing agent, so too the actualization of the sensible object and the sense-organ is expressed in the latter. The actualization of a sonorous body is sound or sounding; the actualization of the hearing organ is audition or hearing. For hearing is twofold and sound is twofold, and the same statement applies to other senses and sense-objects, j In some instances the two have a distinct name, as e.g. hearing and sounding; in other instances one of the two is nameless. For the actualization of sight is called seeing, but the actualization of colour has no name; the actualization of the organ of taste is called tasting, while the actualization of flavour is nameless. Inasmuch as the actualization of the sense-object and the sense-organ is one and the same process, although the two things differ in their essential nature, it is necessary that hearing and sound, in this sense, should be both either destroyed together or preserved together; and the same applies to flavour and taste, and to the other sensecorrelates. This necessity does not, however, apply to the sense-correlates in their potential signification. On the contrary, the old naturalists were wrong here, supposing, as they did, that neither white nor black has existence apart from sight, nor flavour apart from In one way they were right and in another wrong. For lo owing to the fact that sense and sense-object have a twofold signification, namely that of potentiality and that of actuality, their dictum was applicable to the one meaning, but not to the other. They applied it, however, to things absolutely which are not predicated absolutely.

If harmony is voice of a certain kind, and if voice and hearing are in a sense one and the same, and in another sense not one and the same, and if, further, harmony is a relation of parts, hearing must likewise be a relation of parts. It is for this reason (i.e. because sensation is a kind of proportion]) that every excessive stimulus, whether acute or grave, disturbs hearing. In like manner the sense of taste is disturbed by excessive d flavours, the sense of sight by extremely glaring or extremely faint colours, smell by excessive odours, whether cloying or acrid. Consequently, qualities are agreeable when, pure and unmixed, they are reduced to proportion, as e.g. the pungent, sweet, or saline, or in the domain of touch, the warm and cool. It is then that properties are pleasant. In general, the mixed, rather than the acute or grave alone, is harmony. And sensation is proportion. Excessive stimuli either produce; pain or pervert the organ. Every sense is directed to its own peculiar senseobject; it is given in the sense-organ as such, and it distinguishes the different qualities in its appointed sense-object, as e.g. white and black in the case of sight, sweet and bitter in the case of taste. And the same can be said of other senses. Now inasmuch as we necessarily distinguish an object by contact. Neither is it possible by means of the distinct senses to judge that sweet is different from white, but it is necessary that both these qualities be cognized by some one faculty; otherwise it would be like my perceiving one thing and you another, and so proving that they are different. i6 single faculty must, therefore, say that they are different. For the sweet is actually different from the white. One and the same faculty, then, must affirm this. And as this faculty affirms, so do thought and perception agree. It is clear that we cannot judge of distinct qualities by different senses, and we can conclude from this that we cannot judge of them at distinct intervals of time. For it is one and the same principle in us which says that the good is different from the bad. Further, it says that they are different and distinct at the moment when this affirmation is made.

And when is not used here in an accidental sense, by which I mean: when does not apply merely to the time of the affirmation, e.g. I say now that it is different, but it applies also to the thing affirmed, I say that it is different now, i.e. the time applies to the assertion and thing coincidently. So the two elements here are inseparable, and are given in an indivisible moment of time. It is impossible for the same thing or an indivisible entity to undergo opposite processes simultaneously and in an indivisible moment of time. For if sweetness stimulates sensation or thought in one way, then bitter stimulates it in an opposite way and whiteness in some other way. Is, then, the judging something at once numerically indivisible and inseparable, yet separable in the mode of its existence? There is a sense, then, in which as divisible it perceives the divisible, and a sense in which as indivisible it perceives the indivisible. For in its significant being it is divisible, but spatially and numerically it is indivisible. Or is this not possible? Potentially, indeed, one and the same indivisible thing may contain opposite properties, but not in actuality; in its realized self it is separate, and it is impossible for a thing to be at the same moment both black and white. So that it is not possible for even the forms of experience to undergo these opposites, if sensation) and thought be such Kather the case here is similar to what some call a point, which is divisible or indivisible, as one regards it in its single or dual In so far as it is indivisible, the judging principle is oiie and coincident with perception; in so far as it is divisible,' it is not one, for it employs twice and simultaneously the same mark. In so far as it employs a terminal mark as two, it distinguishes two things, and these are separable for it as a separable In so far as it regards the point as one, it judges singly and coincidently with perception. In this way, then, let us state our definition of the principle by virtue of which we say that animals are sentient beings.

Inasmuch as the soul is defined mainly by means of two attributes, namely by locomotion on the one hand and by thought, judgment, and sensation on the other, it is supposed that thought and reflexion are a kind of sensation (for in both instances the soul discriminates and cognizes some reality), and even the old writers tell us that reflexion and sensation are identical, as e.g. Empedocles, who said:" Wisdom groweth in man in the face of a present object"; and in another verse:" Hence is given unto them the power of reflecting ever and anon on diverse things"; and the words of Homer have the same meaning:" Such is the mind." For all of these ancient writers regard thought as something somatic, like sensation, and believe that both in sensation and thought like is apprehended by like, as we said in the beginning of this They should at the same time have spoken of error, for to animals this is more natural than truth, and their souls pass most of their existence in error. According to this theory, as some hold, either all phenomena must be true or else error consists in the contact of the unlike, for this is the opinion that is opposed to the cognition of like by like. Further, in this case error and knowledge of opposites seem to be identical. That sensation and reflexion, therefore, are not identical is evident. For all animals share in the one, but few only in the other. Neither is in which right and wrong are determined, i.e. right in the sense of practical judgment, scientific knowledge, and true opinion, and wrong in the sense of the opposite of these, — thought in this signification is not identical with sensation. For sensation when applied to its own peculiar objects is always true, and! is inherent in all animals; but it is possible for discursive) thought to be false, and it is found in no animal which! is not also endowed with reason. Imagination, too, is; different from sensation and discursive thought. At the same time, it is true that imagination is impossible without sensation, and conceptual thought, in turn, is impossible without imagination. That'fthought)and conception, however, are not one and the same is evident.

For I' tion is under our control, and can be stimulated when wish (for it is possible to call up before our eyes an imaginary object, as one employs images in the art of mnemonics). Conception, on the other hand, is not under our control. For it must be either false or true. Furthermore, when we conceive that something is terrible or fearful, we have at once a corresponding, feeling, and the same may be said of what inspires courage. But in the case of imagination we are in the same condition as if we were to place a terrible or a courage-inspiring object before us in a picture. In conception itself there are distinct forms, such as knowledge, opinion, reflexion, and their opposites, concerning whose different meanings we shall speak later. Since thinking differs from sense-perception, and in g one signification appears to be imagination and in another signification conception, we must proceed to the treatment of the latter, after we have defined imagination. If imagination means the power whereby what we call a phantasm is awakened in us, and if our use of language here is not merely metaphorical, then imagination is one of those faculties or mental forces in us by virtue of which we judge and are capable of truth and error. And these faculties include sensation, opinion, scientific knowledge, and reasoning. IThat imagination is not to be confounded with sense-perception is plain from the following lo considerations. Sensation is either a mere power or a distinct act, like sight and seeing, but imagination is present when neither of these conditions is realized, viz. in the phantasms of dreams. Again, sensation is always present, but this is not true of imagination. If in reality it were identical with sensation, then all animals would have imagination. This does not seem to be the fact, as we find in the case of the ant, the bee, and the worm. Again, sensations are always true, while imaginations are u for the most part false. In the next place, we do not say when we are accurately observing a sense-object, that we imagine it to be a man.

We say this rather when we do not clearly perceive [and when the perception may be true or false], and as we said above, we see imaginary pictures even when our eyes are closed. But neither is imagination one of those faculties whose deliverances are always true, as e.g. scientific knowledge and reason. For imagination can also be false. It remains to be considered whether it is opinion, for opinion can be either true or false. Opinion, however, is followed by belief (for no man can have an opinion and not believe what he opines), and none of the lower animals possesses belief, although imagination is found in many of them. [Again, every opinion is followed by belief, as belief is followed by persuasion, and persuasion by reason. Now, some of the lower animals have imagination, but none of them have reason.] It is plain, then, that imagination is not opinion combined with sensation, nor mediated by sensation, nor a complex of opinion and sensation, and, for the same reason, it is clear that opinion has for its object nothing else than what sensation has for its object. I niean e.g. that imagination is the complex of an opinion of whiteness and a sensation of whiteness, and not the complex of an opinion of goodness and a sensation of whiteness. To imagine, therefore, is to opine what, strictly regarded, is a sense-object. Again, there arefalse appearances when we have correct conceptions, e.g. in the case of the sun which appears to be a foot in diameter, whereas we believe it to be larger than the inhabited earth. The consequence is that we must either have thrown aside our true opinion which we held, without the thing having changed and without any forgetfulness or change of conviction on our part; or if one still holds it, it is necessary that the same opinion be both true and false. But an opinion has become false in a i6 case where an object, without our knowing it, has changed. Imagination, then, is not one of these faculties nor a derivative of them.

Since one thing when moved can communicate motion to another, and since imagination is held to be a form of motion which does not come into existence without sense-perception, but only in sentient creatures or in reference to objects to which sensation applies, and since motion is produced by the action of sense-perception, and this motion must be equal to the strength of the sensation, one can affirm that the motion of imagination! would never be possible without sensation nor could itj take place in non-sentient creatures. Further, the one who experiences it can act and be acted upon in many ways, and one's experiences may be true or false. This truth or falsehood is due to the following causes. Senseperception is true when it concerns its own peculiar objects; at any rate, there is involved in this case, the least possible amount of error. In the second place, sense-v perception may concern the accidental, and here error; begins to be possible. One is not mistaken in saying that a thing is white, but if one says the white object is this or that particular thing, error arises. In the third place, error applies to common properties and concomitants of the accidental, in which peculiar properties are involved. I mean e,g, motion and magnitude, which are accidental > properties of sensible objects, and concerning which we are especially liable to error in sense-perception. The motion set up by the activity of sensation will differ in terms of the three following forms of sense-perception. The first movement is when the sense-perception continues present, and this is true; the other two may be false whether the object is present or withdrawn, but are especially liable to error when the sense-object is removed. If imagination contains nothing but the elements named and is what we have described it to be, it would be a movement stimulated by actualized sense-perception. Since sight is our principal sense, imagination has derived its name from light, because sight is impossible without light. Because images persist and resemble sense-perceptions, animals regulate their actions to a large degree by imagination, some of them because they are incapable of reason, as the lower brutes, others because reason is sometimes veiled by passion, disease, or sleep, as is the case amongst men.

Concerning imagination, what its nature is and what end it subserves, let the foregoing suffice.: () opinion is accompanied by belief, which is not true of imagination; () we may have a correct opinion about a thing, but our imagination about the same thing may be quite at variance with the opinion (). Further, it is not a combination of opinion and sensation as held by Plato, because opinion and imagination may contradict, and consequently, in this case, must exclude, each other. When the image is recognized as that of an object perceived in the past, with a consciousness of time, the imagination is then termed memory (fiurifxr)) and the image is /jLinjfidvevfxa. If the reproduction of the image is conscious and deliberate, the act is recollection <ns). Inasmuch as the latter act requires reflection, only man is endowed with it, although memory is shared by the brutes (De mem. fi). The imagination in its reproductive function is the source of memorj' recollection, and the association of ideas; in its productive or constructive function, it is the origin of fancies and distorted pictures in j dreams, fever, and melancholia. Without it language would be im-/ possible (), and it gives clearness to conceptual thought by clothing this in the schemata of sense (;;). Regarding that part of the soul by virtue of which one knows and reflects, whether it be a distinct part or whether it be distinct only notionally and not really, we X have now to consider what its differential mark is, and by what process thinking is exercised. If thinking is like sense-perception, it would be either a kind of impression made by the object of cognition or some analogous process. It must, then, be impassive and yet receptive of the and in its nature potentially like to the i object of thought without being this object; and as the sense-organ is related to the object of sense, in a similar way thought must be related to the object of thought. > Reason must, therefore, be unmixed, as Anaxagoras says, since it thinks everything, in order that it may rule, i.e. in order that it may It is the nature of thought to preclude and restrain the element that is foreign and adjacently seen. Its nature is, therefore, exclusively potentiality.

What we call reason in the soul (by reason I mean the instrument by which the soul thinks and forms V' conceptions) is, prior to the exercise of thought, no reality at all. It is, therefore, wrong to suppose that reason itself is mixed with the body. For in that case it would have certain qualitative distinctions such as warm or cold, or it would be a sort of instrument, like a sense-organ. But in point of fact it is nothing of the kind. Certain have happily called the soul the place of ideas, only this description does not apply to the soul as a whole, but merely to the power of thought, and it applies to ideas only in the sense of potentiality, and not of It is evident from the sense-organ and from the nature of sensation, that the term impassivity is employed in a different meaning in sensation and in thinking. For sense-perception cannot take place when the sensestimulus is excessive, as one does not hear sound in the midst of loud noises, neither can one see nor smell in the midst of excessively bright colours and strong odours. On the other hand, when the mind thinks a very profound' thought, it thinks not in a lesser but in a deeper degree minor details. For the power of sensation is not/' independent of the body, while the mind is separable.J When reason becomes its several objects in the sense in which an actually learned man is said to be learned (and this takes place when he can exercise knowledge through his own agency), even then reason is in a certain sense potential, although this potentiality differs from that which preceded learning and discovery. In the latter case, potentiality signifies the capacity of thinking itself There is a difference between concrete magnitude and the ultimate nature of magnitude, between water and the ultimate nature of water (the same distinction can be applied to other instances, though not to all, for in some cases they are identical). Concrete flesh and the ultimate nature of flesh one judges either by a different and distinct faculty or by the same faculty under differing conditions. Flesh is not separate from matter, but like a snub-nose, it is a particular thing in a given something.

By means of a sense-organ one) discriminates heat and cold and those qualities of which flesh is a sort of register. On the other hand, reason judges of the essential nature of flesh either by a dififerent and distinct faculty, or in the way in which a bent line is related to itself when We refer the straight line as we do the snub-nose to abstract for they are both associated with the continuous. But the essential notion of a thing, if straightness and the straight line are different (and they are two things), is apprehended by a different power. The mind, then, judges in the two cases by means of a different power or by means of a power differently lo conditioned. In a word, therefore, as there are things abstracted from matter, so there are things that concern the reason. If the mind is simple and impassive, and has nothing in common with anything else, as Anaxsays, and if thinking means to be somehow II impressed, one might ask, How will thought be possible? For it is only in so far as there is something common to two things that the one appears to act and the other to be acted upon. A further question might be raised, viz. whether the mind itself is the object of thought. If it is, mind will then either be found in other things, unless it is the object of thought in some way different from other objects, and unless the object of thought is a specific and single thing; else it will have a mixed composition which makes it like other things, the object of thought. According to our former definition, to be affected in reference to a common element/ means that the mind is potentially the object of thought, though perhaps not actually so until thought takes place. It must be that the case here is similar to that of the tablet on which nothing has been actually written. This is what takes place in the case of mind, and it is the object of thought as other things are. Where entities are without matter, the subject and object of thought are identical. Speculative thought and the thing speculatively known are one and the same.

The reason why thought is not continuous must be investigated. On the other hand, when entities are material they are severally the object of thought only potentially; mind i8 not an element in them (for reason is the potentiality of such objects in abstraction from their matter), whereas it is in the reason itself that the object of thought will be found. In the whole of nature there is on the one hand a material for every kind of thing (and this is what all things are in their potentiality), and another factor which is causative and productive of things, by virtue of its making all objects, as art stands related to the matter it employs. These distinctions must also hold good when applied to the soul. Reason is of such | character that on the one hand it becomes all things, and on the other creates all things, in this respect resembling a property like light. For light in a certain sense converts potential into actual colours, and reason, in the present meaning, is separate, impassive, and unmixed, being in its essential nature an energizing force. Now, action is always higher than passion and causal force higher than matter. Actual knowledge is identical with its object. Potential knowledge, on the other hand, pre-exists in the individual; regarded absolutely it does not so pre-exist. For mind does not at one moment think and at another not. In its separated state alone reason is what it is, immortal and eternal. We have no memory of it, because this part of reason is impassive. The passive reason, on the other hand, is perishable, i and without it there can be no (), pp.. When thought is applied to indivisible terms, error does n,ot arise. Where error and truth are both found is just in the combination of thoughts into a sort of unity. Empedocles e.g. says;" Wherefore the heads of many creatures sprang into life without necks," and later on by the attraction of Friendship they were joined together. So, too, these disjoined ideas are combined together by the reason, as e.g. the ideas of the incommensurable and the diagonal. If the ideas refer to the past or to the future, the element of time is added in <J the mind and combined with the ideas. Error is always due to the combination.

For even in the case where one might think the white not to be white, one has made the combination of the' notwhite.' It is further possible to apply disjunction to everything. It is not only possible for the statement Cleon is fair' to be true or false, but this may be applied to the past or to the future. The unifying principle is in every case the Since the simple or indivisible may be looked at from two standpoints, viz. either as potentiality or as actuality, there is nothing to prevent the mind from thinking the indivisible when it thinks of extension (which in its actual state is indivisible), and when it thinks it in an indivisible moment of time. For divisibility and indivisibility apply to time just as they do to length. It is, therefore, impossible to say what the mind thinks in each half of a time-division. For the half does not exist, except in potentiality, if the division has not been made. But in the act of thinking each half separately, the mind divides the time also, and then the time corresponds in its division to the two If, however, the mind thinks the object as a whole composed of two halves, it does this also with regard to time in its relation to the two halves. That which is not quantitatively but only notionally indivisible, the mind thinks in an indivisible time and by an indivisible power of the soul. It does this, however, accidentally and not in so far as the factors of thought and time are divisible, but in so far as they are indivisible. And there is also in these cases an objective factor which is indivisible, although perhaps not a separate entity, that gives a unity to time and extension. And this is likewise true of everything that is continuous, whether in time or space. The point and everything obtained by division, and whatever (like a point) is no longer divisible, are explicable in terms of Similar reasoning may be applied to other cases, as e.g. the way in which we know evil or black. For we know them somehow or other by means of their contraries. But the knowing mind must be these things potentially, and they must be reduced to unity in the mind itself.

If, however, in the case of any causal principle there is no opposite, then it knows itself, and is in actuality and is separate. A predication, as e.g. an affirmation, asserts something of something else, and is in every instance either true or false. This does not apply to the mind always, but when the mind asserts what a thing is in its essential nature and not what attaches to something as a predicate, then it is true. And just as sight is true when it concerns its own proper object, and on the other hand the opinion that a visible white object is or is not a man may not always be true, so it is with all immaterial entities. Actual knowledge is identical with its object. Potential knowledge is earlier in time in the individual, but taken absolutely it is not earlier in time. For all becoming proceeds from actual being. The sensible object appears to convert the potentially sensitive organ into an actually sensitive organ. For the sense-organ itself is not affected, and undergoes no change. That is the reason why we have here to do with a form of motion different from motion in the ordinary sense. Motion was defined as a realization of the incomplete, but motion, absolutely regarded, is a different kind of activity, viz. the activity of the perfected thing. Mere sense-perception, then, is like a simple expression or a simple thought; when, however, the sensation is pleasant or painful, and thus corresponds to affirmation or negation, the thing is pursued or avoided. To feel pleasure or pain signifies to experience an activity in a mean function of the sense-organ relative to good or bad as such. Avoidance and pursuit in their actual natures are identical, and the appetitive power whereby we desire or pursue a thing is not different from the power whereby we avoid a thing. They do not differ from each other or from the sensitive faculty. Only the expression of their being is different. Images are employed by the conceptual reason as sensepresentations are by the sentient faculty. When the mind makes an affirmation or negation touching the good or bad, it avoids the one and pursues the other.

The soul,_ therefore, never thinks without the use of As the air produces such or such an effect on the pupil of the eye, and the pupil in turn produces another effect (the same illustration may be applied to hearing), and yet the ultimate interpreter or medium of sensation is a single power whose being is expressed in several ways, ([so it is with in reference to thought.]) As to the faculty by which we discriminate sweet and warm, although the problem has been mentioned above, it must be again discussed as follows. There is some' unitary principle, and this unitary principle has the character of an ultimate term. Its deliverances are reduced to unity by means of comparison and numerical statement, and are related to each other as the outward things are related to each other. The question as to how the mind judges like qualities, does not differ from the question as to how it judges opposite qualities such as white and black. Let A, the objectively white, be related to B, the objectively black, as the idea C is related to the idea D, or it may be stated conversely. Now, if the ideas CD attach to a certain thing, they will be related to each other ([in the concept]) just as AB are related to each other, — they will form one and the same thing, though not identical in mode of being; and the former combination (CD) is analogous to the latter (AB) The same reasoning holds in case one were <> to apply A to a sweet object, and B to a white object. The reasoning mind thinks its ideas in the form of images; and as the mind determines the objects it should pursue. or avoid in terms of these images, even in the absence of sensation, so it is stimulated to action when occupied with them. For example, when one sees that a beacon is lighted, and observes by means of the' common sense' that it is in one comprehends that an enemy is near. Sometimes by means of the images or ideas in the soul the mind reasons as a seeing person, and takes thought for the future in terms of things before one's eyes.

When the mind there in its world of images says that a thing is pleasant or painful, here in the world of things it pursues or avoids, — in a word, it acts. Apari' from action the true and false belong to the same category as the good and bad. They differ, however, in the absolute character of the one and the relative character of the other. The mind thinks abstractions, as e.g. when it thinks the snub-nosed, which in one sense is a snub-nose, and in another sense, if one thinks it actually, one would think it as a curvature without the flesh in which the curvature is found. So too with mathematical figures, though in actuality not separate from bodies, the mind thinks them as separated, when it thinks them. In a word the mind is the thing when actually thinking Whether or not it is possible to think any abstraction when the mind itself is not separate from magnitude, must be investigated later. The true and false are universally valid, regarded merely from the standpoint of cognition, but when regarded in the light of wrong and right they are relative to the individual. Or the passage may have another significance, viz. the notions of good and bad aflfect our wills and stimulate to action only when they are referred to particular objects. In the act of thinking, subject and object are identical; the thinking mind is the idea thouglit. Looking at the main features of what has been said of the soul, let us reiterate the statement that it is in a sense all reality. For everything, whether sensible or intelligible, is psychical; intelligible objects are in a sense knowledge, and sensible realities are sensations. How this is possible remains to be investigated. Conceptual knowledge and sense-perception are each divided into two kinds, corresponding to their objects; potential knowledge corresponding to potential objects, and actual to actual. The sensitive and conceptual powers of the soul are, potentially regarded, the objective things, viz. the intelligible and the sensible. The soul, then, must be either the things themselves or their form. It cannot, of course, be the things themselves. For a stone is not in the soul, but the form or idea of the stone.

Consequently, fl the soul is to be thought of as a hand; for a is the instrument of all instruments, and the reason is the form of all forms and sensation in the form of all sensible realities. Since, however, there is no object, as is supposed, apart from sensible magnitudes/ it follows that intelligible objects, — I mean abstractions, as we call them, on the one hand, and the qualities and conditions of the sensibles, on the other, — must be sought in the sense-forms. For this reason, also, it would be impossible for one to learn anything or understand anything without sense-perception, and when one contemplates a thing, one is forced to contemplate it in conjunction with an internal image. These images are like sensepresentations, with the exception that they are without matter. Imagination is different from affirmation and negation; for the true and the false are the combination of ideas into a In what way are the primary ideas to be distinguished from imagination? Or is it true that these ideas are not themselves images, yet they cannot be produced independently of images? Since the soul of living beings is defined in terms of two powers, viz. the power of judgment (which is the function of thought) and the power of sensation on the one hand, and the power of locomotion on the other, let the above sufi&ce for our treatment of sensation and thought, and let us now consider the moving principle and ask what part of the soul it may be. The further question arises whether it is an individual part of the soul and separate, either concretely or notionally, or whether it is the entire soul. If it is only a part, we must ask whether it is a peculiar part and distinct from those usually described and already mentioned here, or whether it is one of these. There is a difficulty at the start concerning the sense in which we are to employ the term parts of the soul, and concerning their number. For in a certain way they seem to be innumerable, and not merely confined to those which certain writers distinguish, viz. reason, will, and and others classify as rational and irrational elements.

For according to the differences by which they distinguish these parts, there seem to be other parts that are even more distinct from each other than these, concerning which we have just now spoken, viz. the nutritive part, which is found even in plants as well as in all animals, and the sensitive part, which one could not easily classify either as irrational or as rational. Again, the power of imagination, which is different in its mode of being from the others, appears to be a distinct part, but in what particular it is identical with or different from the others, is very difficult to say, if one is to regard the parts of the soul as existing independently of one another. In addition to these, there is the desiderative part, which both notionally and functionally might be supposed to differ from all the other parts. And yet it would be absurd to sever this from the others. For it is in the thinking element that volition arises, and in the irrational element we have desire and passion. But if the soul has three distinct parts, then the desiderative element must be in all of them. Moreover, the question again comes up which we raised just now, viz. what is the principle in animals that produces locomotion? One might suppose that it is the generative and nutritive powers, found in all living things, that produce the motion involved in growth and decay common to them all. The subjects of inspiration and expiration, sleeping and waking, must be investigated later, for all of them present great difficulties. But regarding locomotion, we must inquire what it is that gives animals the power of progressive movement. It is evidently not the nutritive power, for progressive, movement is always towards some end and accompanied' either by some image or desire. For where there is no desire or revulsion, there is no motion, excepting where external force is used. Further, if motion were due to the nutritive power, plants would be capable of locomotion and would have some organic member adapted to this motion. Soo, too, it cannot be the sensitive power that is the source of motion; for there are many animals which have sensation and yet, throughout their existence, are stationary and motionless.

If, then, nature creates nothing in vain, neither does she omit anything that is necessary, save in cases of deformed or imperfect beings. And such animals as we have in mind are normal and not deformed. A test of perfection is the capacity to reproduce, to reach the prime of growth, and then decline. Consequently, such animals should also have organs of But neither thinking power nor what we call reason the cause of animal motion. For the contemplative power does not think upon what is to be carried into execution, neither has it anything to say touching what is to be avoided or pursued, whereas motion always belongs to that which pursues or avoids an object. On the contrary, when one contemplates anything, the mind does not bid one pursue or avoid; e.g. the fearful or pleasant is often the subject of thought, but the feeling of fear is not suggested; the heart, however, is agitated, or if the feeling is pleasure, some other organ is stirred. More than this, even when the reason commands and intelligence tells us to avoid or to pursue a thing, motion does not follow, but one acts according to one's desire, like an intemperate man. We observe, in general, that the man versed in medicine does not heal, because it is something other than science that has the power of acting according to the principles of Neither, again, is desire the dominating in this motion; for continent men, though filled with desire and appetite, do not do the things for which they lust; on the contrary, they follow reason. There are two powers in the soul which appear to be moving forces — desire and reason, if one classifies imagination as a kind of reason. For many creatures follow their imaginations contrary to rational knowledge, and in animals other than man it is not thought nor rational procedure that determines action, but imagination. Consequently, both of these, reason and desire, can produce locomotion — I mean here the reason that considers and is concerned with It differs from the theoretical reason in having a moral end. Every desire aims at something. It is the final end that is the initial, cause in So that it is reasonable to regard these two principles, viz. desire and practical reason, as' motor forces.

For the object of desire sfimulates us, and through it reason stimulates us, because the object of desire is the main thing in the practical reason. Imagination, too, when it stimulates us to action, does not do so independently of desire. The one single moving force is the object of desire. For even if there were two moving powers, reason and desire, still they would produce movement in accordance with some common idea. As a matter of fact, however, reason does not appear to produce movement independently of desire. For volition is a form of desire, and when one is prompted to action in accordance with reason, the action follows also in accordance with volition. But desire prompts actions in violation of reason. For appetite is a sort of desire. Reason, then, is in every case right, but desire and imagination may be right or wrong. It is, therefore, always the object of k desire that excites action, and this is either the good or the apparent good — yet not every good, but only the i good in conduct, and this practical good admits of variai tion. Evidently the psychical power which excites to action has the nature of desire, as we call it. In analysing the elements of the soul, if one analyses and distinguishes them in terms of powers, they become very numerous, as e,g, the nutritive, sensitive, rational, deliberative, and desiderative. For these differ from each other more than do the desiderative and spirited elements. Although desires arise which are opposed to each other, as is the case when reason and appetite are opposed, it happens only in creatures endowed with a sense of time. (For reason, on account of the future, bids us resist, while desire regards the present; the momentarily pleasant appears to it as the absolutely pleasant and the absolutely good, because it does not see the future). The moving principle, which is the desiderative faculty as such, is specifically one, though numerically several motive forces may be included in it. The main element here is the object of desire (for this by being the object of thought or imagination excites movement, while it is itself unmoved). There are, then, three terms to consider here, first the motor power, secondly the instrument of motion, and thirdly the object set in motion.

The motor power is twofold: on the one hand, it is an unmoved element, and on the other, a moving and moved element. The unmoved element is the good to be done; the moving and moved element is the desiderative faculty (for the desiderative faculty in so far as it desires is moved, and desire in process of realization is a form of motion); the object which is set in motion is the animal. The instrument by which desire effects motion, is of course the body, and consequently it must be investigated where we have to do with functions which are common to the body and the One may, however, say summarily here that motion is organic in those cases where beginning and end are one, as e.g. in a joint. For here the convex and concave are beginning and end. Therefore the one is at rest and the other in motion, and while they are notion - ally distinct, they are concretely inseparable. Everything is set in motion by push or pull, and there must be consequently, a fixed point, as the centre in a circle, and this is the initial point of In a word, then, as we said before, an animal in so far as it is capable of desire is capable of self-movement. Desire, however, is not found apart from imagination, and all imagination is either rational or sensitive in origin, and the lower) animals share in it. Analogously, the reason is not itself in movement but is that from which movement proceeds. The attractive thing on the one hand, and i the commanding reason or desiring mind on the other, constitute the push and pull in animal life. We must inquire also into the nature of the moving principle in those imperfect animals which possess only fl the sense of touch. Is it possible for them to have imagination or desire? They appear to feel pleasure and pain, and if these are felt they must necessarily have desire also. But how could they have imagination? Or are we to say that just as their movements are indefinite, so too this power is possessed by them, only it is indefinitely developed. Imagination derived from sensation is, as we said before, found in the lower animals, but deliberative imagination is found only in those animals which are endowed with reason.

For whether one shall do this or that is, of course, a matter of deliberation, and there must be some single instrument of measurement at hand (for it is the greater good that is to be pursued), and so the mind is able to make a single representation out of several images. The ground for supposing that animals do not have opinion is that they do not have the faculty for drawing rational conclusions, and opinion involves this. Consequently, their desire lacks the deliberative quality. Sometimes the desire overpowers the deliberative element in man and excites to action. At other times the will overpowers the desire, and again, like a ball tossed to and fro, one desire overpowers another, as in the case of intemperance. In the workings of nature the higher element always has the greater authority and is the moving power. There are, then, three forms of The faculty of conceptual thought is not moved, but remains at rest. Since we have two principles in conduct, on the one hand the general and notion, and on the other hand the particular notion (of which the one says a man of such and such a kind shall act in such a way, and the other that this particular man — and I am that particular man — shall act in a given way), it is the latter notion that incites to action, but the general one does not. Or both of them combined may lead to action, although the general notion is quiescent, and the particular one active. Every living thing must have a nutritive soul in order that it may live and continue to live from birth until death. What has been born must grow, reach its complete development and decline, and this is impossible without food. A nutritive power must, therefore, be given to everything that grows and dies; but sensation is not necessary to all living Whatever has a simple body cannot be endowed with the sense of touch (neither is animal life possible without touch), and whatever is incapable of interpreting the forms of things without their matter is also incapable of touch. An animal must have sensation, if it is true that nature creates nothing in vain. For everything in the natural world exists for a purpose, or is the condition of something that exists for a purpose.

If, then, a body which is endowed with the power of movement were deprived of sensation, it would perish and would not attain the end for which nature strives. For how will it nourish itself? Amongst organisms fixed to one spot, a source of food is provided for them from which they naturally grow. It is, however, impossible for a body that is not stationary, and is produced by generation, to have life and a thinking mind, and yet not have sensation. No more is this possible in bodies that are not produced by For to what end will they lack sensation? It must be because such lack will be better either for their soul or body. But neither is true. For the one will thereby think none the better, nor the other last any the longer. Consequently, no moving body has a soul that is unendowed with sensation. If, however, the t5o3y is endowed with sensation, it must be either single or mixed. The former is impossible; for in that case it could not have touch, and touch is necessary. That is clear from the following grounds. Since every living creature is an animated body, and every body is tangible, and tangible is that which is sensed by means of touch, it follows necessarily that the animal body must be capable of the sensation of touch, if the animal is to persist in life. The other senses, such as smell, sight, and hearing, perceive through other media than the tangible body. If, however, an animal on being touched were to experience no sensation, it would have no power to avoid certain things and pursue others. And if this were the case, the animal could not survive. Therefore, taste is a kind of touch, for it is concerned with food, and food is a tangible body. Sound, colour, and smell, on the other hand, furnish no nutriment and do not contribute to growth and decay. Consequently, taste must Even the eternal and unbegotten bodies (stars) have the power of sensation.' Touch implies the duality of perceiving soul and tangible body. be a sort of touch, because it is a sense that concerns a tangible and nutritive object. Both of these senses ([touch and taste]) are necessary to every animal, and it is evident that no animal can exist without touch.

The other senses exist for the sake of higher well-being and are not found indiscriminately in animal species, but only in certain of them, viz. in such as are capable of progressive motion, and here they are necessary, For if such an animal is to survive it must not only apprehend an object by touching it, but must be able to do this at a distance. This result would be attained if the animal were capable of sensation through a medium, and the medium were impressed and set in motion by the sensible object, and if the sense-organ were in turn stimulated by the medium. Just as a body moving in space causes a transfer of energy up to a certain point, and the propelling body causes another body to become propulsive, and through the mediate term motion is continued; and as the initial agent moves and exerts propulsion without being itself propelled, while the last body in the series suffers propulsion without exerting it and the intermediate bodies (of which there may be many)," both suffer and exert it; so it is also with the process of change ([in sensation]), excepting that here change may take place while the object continues on a single spot. For example, when one dips an object in wax, movement of the wax takes place up to the point that immersion has taken place. A stone, however, would not be moved in this way at all, while water would be moved more lo than wax. The most mobile element, both in its power to receive and communicate motion, is the air, provided it is confined and is a unit. Concerning the phenomenon of the reflection of light, then, it is better to suppose that the air, in so far as it is a continuous mass (and this is the case upon every smooth surface), becomes charged with form and colour, rather than that the visual image after it has once issued from the eye is reflected back to the Consequently, the air reacting on the eye stimulates it, as if the impress in the wax were to penetrate through to its opposite The reference is to Empedocles, who believed there was a dual eflflux or emanation from the eye and from the object (cf. Platos Menon 76c ff., Aristot. De sensu fF.) and to Plato. Evidently an animal body cannot be simple.

I mean that it cannot e.g. consist simply of the element of fire or air. For without touch one cannot have any other sensation. Every body endowed with soul has the capacity of touch, as we have already said. All the other elements, excepting earth, might become organs of sensation, but all of them produce sensation by the instrument of intermediary bodies. Touch, on the contrary, appears to act by immediate contact with bodies and hence its name, and although the other sense-organs effect sensation by means of contact, yet the contact is indirect and mediated; whereas touch is the only sense that acts by direct contact. So then no animal body; can be constituted exclusively out of such elements ([as) are fitted for mediate perception]), neither can it be constituted exclusively out of earth. For touch is, as it were, the mediator of all tangible things, and the senseorgan is capable of receiving not only all the various qualities that attach to earth, but also the hot and cold and all other tactual distinctions. Therefore we have no sensation in our bones, hair, and other such parts, because they are constituted out of the element of earth. For this reason also plants have no sensation, because they are composed of earth. Without touch there can be no other sensation, but the organ of touch is not composed exclusively of earth nor of any other single element. It is plain, then, that this is the only sense, the deprivation of which necessitates the death of animals. For neither is it possible for anything that is not an animal to have this sense, nor is it necessary for anything that is an animal to have any sense beyond s it. Therefore, other sense-qualities, such as colour, sound, and smell, do not by their excess destroy an animal; they only destroy the sense-organ, except in some accidental case, as where a push or blow accompanies the sound, and when other objects are set in motion by sights and smells which, by their contact, work destrucFlavour, in so far as it is conjoined with a tactual works destruction by virtue of this latter. But excess in tangible qualities such as heat, cold, or hardness, destroys the animal.

For the excess of every sensible quality destroys the sense-organ, so that the tangible destroys the tactual sense, and it is in terms of this that life is defined. For it has been demonstrated that without the sense of touch a living creature is an impossibility. Consequently, excess of tangible impressions not only destroys the sense-organ, >' but also the animal itself, because this sense is the solerequisite to animal life. An animal possesses the other senses, as we have said/ not for the sake of life but of a higher life. It has sight, e.g. in order that it may see, since it lives in a medium of water, or air, or, in a word, in a diaphanous medium, and it has taste, because of the distinctions of pleasant and unpleasant, and in order that it may detect these qualities in its food and so desire it and be moved to obtain it. It possesses hearing in order that information may be communicated to it, and a tongue in order that it may communicate