Aristotle's Psychology

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Aristotle's Psychology (On the Soul, De anima) (1882)
by Aristotle, translated by Edwin Wallace
Aristotle2141726Aristotle's Psychology (On the Soul, De anima)1882Edwin Wallace







Book I.

The Problem of Psychology and the attempts which have been made to solve it.

I. The Problem and its Difficulties

II. Pre- Aristotelian Accounts of Soul

III. Movement as an attribute of Soul

IV. Harmony and Number as Explanations of Soul

V. The Soul not compounded of the Elements of Existence

Book II.

The Nature of Soul and its specific Forms.

I. The Abstract Definition of Soul

II. The Biological Description of Soul

III. The Psychic Faculties and their Relationship

IV. The Nutrient Functions

V. Sense- Perception in its General Features

VI. The Three Kinds of Objects of Sense

VII. The Sense of Sight

VIII. Hearing and Sound

IX. The Sense of Smell

X. Taste and Flavour

XI. Touch and the Tangible

XII. The Essential Character of Sense

Book III.

The Intellectual and Active Powers.

I. The Adequacy of the Senses for knowing all Sensible Qualities

II. The Consciousness of Sensation and the Discrimination of Perceptions as given by Sense

III. Imagination as separating Sense from Thought

IV. Thought and the Intelligible

V. The Creative Reason

VI. The Unifying Work of Thought

VII. Reason as related to its Sensuous Materials

VIII. Ideas as embodied in Things

IX Erroneous explanations of Man's Active Powers

X. Desire and Reason as united in Will

XI. The Comparison of Mental Images in Will

XII. How the Different Faculties are adapted to the Conditions of Human Life

XIII. The Sense of Touch as determining the animal Organism



The acquisition of knowledge is, we conceive, always something high and honourable: but one form of knowledge is superior to another either in virtue of the self-contained simplicity of its truths or by the greater dignity and wondrousness of its contents: and on both these grounds the investigation of the soul might with justice claim a foremost place. And, besides, the knowledge of it is thought to have important bearings on truth generally and especially on nature: for soul is as it were the prime factor in animal existence.

The object of our enquiry is to observe and to discover both the historical development and the essential nature of the soul, and further to find out the phenomena occurring in connection with it — phenomena of which some are thought to be affections peculiar to the soul itself, others, while owing their existence to the soul, are thought to belong to the animal nature taken as a whole. By far in every way the greatest difficulty connected with it is that of reaching some certainty about it. The object of investigation is, it is true, the same here as it is in many other subjects — it is, that is, the question of the essential notion and of the generic character. It might therefore be supposed that there is some one common method applicable to all objects of which we wish to discover the essential nature, just as deductive argument traces out the properties dependent on the genus: and in this case we should have to seek the method in question. But if there be no one common method for finding out the generic character, our procedure becomes still more difficult, as it will then be necessary to settle with regard to each subject of investigation what is the method of enquiry which is appropriate to it And even if it were clear whether some deductive argument or Platonic division or some other method were the right one to apply, yet even so the question from what points we should begin our enquiry is one which offers many difficulties and leaves much room for divergent views, because different conceptions have different fundamental principles, as we see in the difference between the elementary ideas of arithmetic and those of geometry.

The first point however which demands our attention is to determine in which of the higher classes soul is included and what is its generic character — whether, in other words, it is an individual thing and real substance or a quality or quantity or any other of the categories as they have been distinguished. We must further ask whether it belongs to the class of potentialities or is rather a completed actuality — two conceptions between which there is no small difference. Another question, we shall have to ask, is whether it is divisible or free from parts, and whether again all souls are homogeneous or not; and if not homogeneous, whether it is specifically or generically that they differ: for at present writers who investigate the soul seem to confine their observations to the soul of man alone. Special care must be taken to discover whether there is one definition comprehending all the different forms of soul just as the definition of animal applies to all particular animals, or whether the definition is different in respect of each individual species: just as if for example we were to allow a definition of horse, dog, man and God, but should assert that the universal 'animal' either signifies no actually existing thing or is posterior to the particular species, this also holding good of any other common term. Should it however be ascertained that there are not several souls, but merely different parts in the soul, the question rises whether we should begin by investigating the whole soul or should start rather with the parts. And here again it is difficult to determine which of them are really different from one another, and whether we should first of all investigate the parts or their functions — whether we should for instance investigate the act of reasoning or the faculty of reason, the act of sensation or the faculty of sense: and so also in other cases. And supposing we determine to examine first of all the functions, still the further question may be raised whether we should beforehand treat of the objects which are their counterpart — treat, that is, of the object of sense before the faculty of sense, and of the object of thought before the faculty of thought.

The truth however seems to be that it is not only a knowledge of the generic character of anything which helps towards detecting the causes of the properties of substances — as in mathematics the knowledge of straight and curved or the generic character of what is a line or superficies assists us in seeing to how many right angles the angles of the triangle are equal — but even conversely the knowledge of the properties contributes in great measure to a knowledge of the * what ' or the generic notion. When, in fact, we are able to present to the mind's eye all or most of the properties which appear to be connected with an object, we shall be in a position to speak as well as may be about the thing itself: although the starting point of all demonstration consists in knowing what a thing is. And thus all definitions that do not convey a knowledge of the properties attending on an object and do not even render it easy to frame a conjecture regarding them are evidently mere empty phrases such as transcendentalists alone would use.

It is a further question whether the affections of the soul are also all shared along with the soul by the body which contains it, or whether there is in addition something peculiar to the soul itself. This is a question which it is necessary and yet not easy to answer. It appears at any rate that in the great majority of cases the soul is neither active nor passive without the co-operation of the body, for example in being angry, in shewing courage, in feeling appetite — in one word, in being sensitive. Thought seems to be the clearest case of a state peculiar to the soul alone: but if even thought is only the presentation of an image or not independent of such presentation, it would follow that it is impossible for even this act of the soul to be exercised in independence of the body. (^{ then there be any of the functions or affections of the soul which distinctively belong to it, it would be possible for the soul to exist in separation from the body: if, on the other hand, there be no functions or affections so belonging to it, the soul would not admit of separate existence: it would resemble the straight line which as straight has many properties, such as for example to touch a brazen globe in or at a point, while at the same time it cannot touch the globe when separated from its material embodiment: the straight line being really inseparable as always existing along with some body or another. So in like manner the different feelings appear to be all accompanied by some particular condition of the body — such feelings, viz. as anger, meekness, fear, pity, courage, and further joy and love and hate — all of which appear to be accompanied by some particular affection of the body. This indeed is shewn by the fact that sometimes great and evident disasters which have befallen us cause us no irritation or fear, while at other times the feelings are excited by trivial and almost imperceptible mischances, the body being at such times boiling full and in the same state of excitement as in anger. Still more is this evident from the fact that even without the occurrence of anything really terrible people have the same feelings as a person in fright

The feelings then are materialized notions, and they require to be defined in correspondence with this character. The feeling of anger for instance has to be defined as on the one hand a certain movement on the part of such and such a body or part or faculty, and as on the other hand excited by such and such a cause and due to such and such motives.

These facts themselves shew it to lie within the province of the natural philosopher to investigate the soul, either in its whole extent or with reference to the states we have described. Every such state however would be differently defined by the natural philosopher and by the transcendentalism Take, for instance, the question — what is anger? The transcendentalist would define it as the effort after retaliation or the like, the natural philosopher would describe it as a ferment of the pericardial blood or heat. Here then the latter describes the material aspect of the phenomenon, the former states its form and its notion: for it is the notion which constitutes the form of the object, although at the same time it must in order to exist be realized in such and such a matter. Thus in the case of a house, the notion of it would be somewhat to this effect, that it is a shelter fitted to prevent our sustaining damage by winds and rains and violent heats, but the one observer will describe the stones and bricks and timbers, the other will seize upon the form and end which those materials contain. Which then among these is really the true philosopher of nature? Is it he who concerns himself simply with the material aspects and neglects the notion, or is it he who deals with the notion only? Rather, we may answer, it is he who considers the question from both these standpoints. How then, it may be asked, are we to describe each of the enquirers whom we have named? May we not reply that there is really no one occupied only with the qualities of matter, which are inseparable from it, and so far as they are inseparable from it, but that the natural philosopher is concerned with all the functions and properties attaching to body or matter in so far as it is of some specific kind? (When the qualities are not taken in this general way, they are dealt with by a specialist, who becomes, it may be, respecting some of them an artist, as for instance a builder or physician.) When on the other hand the qualities, though inseparable, can be treated abstractly and are not the qualities of any particular kind of body, they fall within the province of the mathematician, and when considered as entirely independent of material substratum, they fall within the province of the metaphysician.

We must return however to our original argument. Our position is that the feelings of the soul are inseparable from the physical substratum of animal life. It is in this way then that anger and fear are related to the material: they cannot like lines and surfaces be treated in complete abstraction from it


The investigation of the nature of the soul requires that we should not only raise difficulties on questions that require settlement; we should also, after we have gone so far, collect the views of those who have previously stated their opinions on the subject: and this in order that we may at once adopt whatever is correctly stated, and also be on our guard against anything that may be the reverse.

The beginning of such an enquiry must be to set forth those characteristics which are generally regarded as the natural attributes of the soul. Now there are two points particularly in which the animate or soul-endowed is thought to differ from the inanimate or soulless — viz. motion and sensation. And these are in fact about the two characteristics of soul which our predecessors have handed down to us.

There are some who maintain that fundamentally and primarily the soul is the principle of movement. They reasoned that that which is not itself in motion cannot move anything else, and thus they regarded the soul as one of those objects which were in motion. Democritus, whose view agrees with that of Leucippus, consequently maintained soul to be a sort of fire and heat. For as the forms of the atoms are as the atoms themselves unlimited, he declares that those which are spherical in shape constitute fire and soul, these atoms being like the so-called motes which are seen in the sunbeams that enter through doorways, and it is in such a mixed heap of seeds that he finds the elements of the whole natural world. The reason why they maintain that the spherical atoms constitute the soul, is that atoms of such configuration are best able to penetrate through everything, and to set the other things in motion at the same time as they are moved themselves, the assumption here being that the soul is that which supplies animals with motion. This same assumption led them to regard respiration as the boundary with which life was coterminous. It was, they held, the tendency of the encircling atmosphere to cause contraction in the animal body and to expel those atomic forms, which, from never being at rest themselves, supply animals with movement. This tendency however was counteracted by the reinforcement derived from the entrance from outside in the act of respiration of new atoms of a similar kind. These last in fact — such was their theory — as they united to repel the compressing and solidifying forces prevented those atoms already existing in animals from being expelled from them: and life, they thought, continued so long as there was strength to carry on this process.

The doctrine ascribed to the Pythagoreans seems also to have this same meaning. Some of them maintained that the soul was the motes within the air, others held that it was what put them in motion. Such motes have been employed to describe the soul, because they present the appearance of continual movement, even though there be a perfect calm.

Similar to the opinion which has just been stated is that which describes the soul as something which sets itself in motion: this and all other like definitions seeming to regard movement as the most distinctive characteristic of the soul. All other things, the supporters of these views imply, are moved in virtue of their soul, but soul is moved by itself; a conclusion which is explained by the observation that nothing is found to produce movement without at the same time moving itself.

Anaxagoras, in like manner, describes mind as the principle of movement: and this indeed must be the account given of it also by any other philosopher who maintains that reason set the universe in motion. Anaxagoras, however, did not regard soul in this light so completely as did Democritus. The latter absolutely identified soul and reason, holding as he did that that which presented itself to sense was real truth: so that (he observed) Homer had well sung of Hector as lying 'with thought apart.' Democritus, this shews, does not employ the term reason to denote a faculty conversant with truth, but uses reason as identical with soul. Anaxagoras himself, however, is less distinct in his identification of the terms. In many places he speaks of reason as the cause of what is beautiful and right, but in other passages he seems to place it on a level with the soul, as when for instance he maintains that it is present in all animals both great and small, both honourable and dishonourable. As matter of fact, however, reason, in the sense of intellect and insight, does not seem to be present equally in all animals or even indeed in all men.

Those then, who have concentrated their attention on the fact that what is animate is in motion have regarded soul as that which is most capable of movement: those thinkers, on the other hand, who have directed their observations to the fact that the soul knows and perceives things existing, identify soul with the elementary principles of all existence, some making those principles to be several in number, others resolving them into this one principle of soul. Thus Empedocles makes the soul to be composed of all the elements, and at the same time considers each one of these elements a soul. His words are as follows:

“Surely by earth we perceive earth, and man knoweth water by water. By air sees air the divine; by fire sees fire the destructive: Yea, love comprehends love, and 'tis through strife dismal we know strife."

In this same fashion also does Plato in the Timaeus construct the soul out of the elements. Like, he there maintains, is known by like, and the objects of knowledge are composed of the elements of existence. To the same effect also is the distinction drawn in his lectures on philosophy, where it is shown that on the one hand the generic or abstract form of the living subject is a product containing the abstract form ' of unity with the primary phase of length and breadth and I depth: and that on the other hand other things are formed in a corresponding manner. An additional mode of explanation is to represent reason as perfect unity, understanding as the two (because it proceeds like a single line directly in one way to one conclusion only), whereas opinion is represented as the number of a superficies, and sense perception as the number of a solid. Numbers, in fact, were said by the Platonists to be the very forms and principles of existence: and such numbers are formed from the elements. And things are apprehended — some by rea son, others by understanding, a third class by opinion, and * fourth order by sense: while the numbers, to which these faculties correspond, constitute the forms or ideas of things themselves.

Since, moreover, the soul was held to be at once a faculty for movement and a faculty for knowledge in this numerical sense: there have been thinkers who have combined the two descriptions and have set forth the soul as a self-moving number.

While however these thinkers agree in reducing the soul to elements or principles, they differ as regards the name and number of the principles: a difference which prevails especially between those who make the principles corporeal, and those who make them incorporeal, and also between both of these and such thinkers as have blended and exhibited their principles as compounded from both sources. They differ too about the number of their principles, some reducing them to one, others regarding them as more in number.

There is a corresponding variation in their views about the soul. The principle of movement they, not unreasonably, regarded as one of the primary elements in the natural world: and consequently there were some who viewed the mind as fire, this being that one among the elements which is made up of the finest parts and is most incorporeal, while further it is the element which is the first to be moved itself and to move other things. The reason for each of these facts Democritus has expressed somewhat neatly. Soul he regarded as identical with reason, and this he held belonged to the class of primary and indivisible bodies, and possessed the faculty of movement by reason of the smallness of its parts and of its peculiar form. Now the form which is most susceptible of movement is the spherical: and of such shape is reason and fire. Anaxagoras, on the other hand, might, as we have said before, sometimes be taken to speak of soul and reason as different from one another: but he really uses the two terms as fundamentally one in nature, with the exception that he makes reason generally the principle of all things. He says at least that * it alone among existing things is simple and unmixed and pure/ At the same time he assigns to one and the same principle both faculties — both knowledge and movement — in saying as he does that reason moved the universe. Similarly also Thales, from what is related of him, seems to have regarded soul as something with capacity of movement, if it be the case that he spoke of the loadstone as possessing soul because it moves iron.

On the other hand Diogenes as also some others resolved soul into air, supposing that this was the subtlest of all things and, at the same time, a principle of existence. This also, they said, was the reason of the knowledge and of the movement of the soul; the faculty of knowledge falling to it as primary and as that out of which all other things are compounded, that of movement belonging to it as being of the subtlest nature. Heraclitus also identifies the soul with his principle in describing it as the " fiery process " out of which he derives other existing things, his ground being that it is that which is least corporeal and in constant movement. He believed in fact with the many that the objects of existence were in continual movement, and the moved, he argued, could be known only by means of the moved. Alcmaeon too seems to have held similar views about the nature of the soul. The soul, he says, is immortal because it is like the immortal: and it is so because it is in everlasting movement, while all things divine — moon, sun, stars and the whole heaven — are for ever in such everlasting movement.

Among cruder thinkers there have been some such as Hippo who have even described the soul as water. This belief seems to have been suggested to them by generative seed which in all animals is moist — Hippo in fact argues against those who assert that the soul is blood on the very ground that the seed is not blood — and this seed they regarded as the primary form of soul. Others again, like Critias, have identified the soul with blood, regarding sentiency as the most distinctive characteristic of the soul and viewing this sensient capacity as due to the element of blood.

Thus, With the one exception of the earth, all the elements have gained a vote. The earth however has been adduced by no one except indeed in such cases as some thinker has explained the soul as formed from all the elements or has actually identified it with them all. Each in fact of the three attributes which we may say are generally used to characterise the soul — movement, perception and incorporeal existence — is supposed to characterize the principles of being. And for this very reason all those who define soul by its capacity for knowledge make it either an element or one of the elements, using (with the exception of one of their number) almost identical expressions respecting it. Like, in short, they say, is known by like; and since the soul knows all things, they constitute it out of all the elements. Thus then those thinkers who admit only some one cause and some one element identify the soul also with some one thing such as fire or air: those, on the other hand, who regard the primary elements of existence as more than one, resolve the soul also into several such elements. Anaxagoras alone says that the reason is not subject to modification from without and has nothing in common with anything beside itself. How being such it is to acquire knowledge and why this is so is a subject on which Anaxagoras has said nothing, nor does the general tenour of his writings help to make it plain. As many further as posit opposites among their primary elements of being constitute the soul also out of contraries; while those who maintain the one or other among contraries—: as for example hot or cold or something of this character — resolve the soul also in a corresponding manner into some one or other of these elements. Hence further such thinkers follow etymologies: some maintaining soul to be the *hot' because it is from the name of heating or 'seething' that the word to live is etymologically derived: others holding soul to be the 'cold' because it is from respiration and cooling that the word for soul has been constructed.

Such then are the opinions which have been handed down respecting soul, as also the grounds on which they rest.


Before proceeding further we must investigate the subject of movement The truth may be that it is not only false to say that the essential substance of soul is of the character assigned to it by those who assert that soul is that which moves itself or is capable of producing movement: it may be an actual impossibility that movement should be a predicate of soul.

That that which causes motion need not itself be in motion is an opinion which has been previously stated. But further there are two senses in which ever\thing that is in motion may be said to be so. The movement may be either directly its own or it may be communicated through something else. The latter expression is applied to all those things that are moved through being within something which is moved, as is for instance the case with sailors in a ship: the sailors not being moved in the same sense as the vessel, because while the vessel is in movement by itself the sailors are so through being in an object that is moved. This becomes evident when we apply it to the limbs. Walking for instance is a movement which belongs distinctively to the feet, it is also a movement which belongs to man as such, and yet it is not true of the sailors at the time when we are considering them.

There are then two senses in which we may say a thing is in motion: and we must now enquire with reference to soul whether in itself it is moved and participates in movement. Now there are four forms of movement — locomotion, alteration, decomposition and augmentation. The motion of the soul must be therefore either one of these four forms, or several of them, or all of them taken together. But further this movement of the soul, if it be not merely an accidental concomitant, must proceed from nature: and, if this be so, space will be an attribute of it, inasmuch as all the movements which we have mentioned occur in space. [But the soul's movement is no mere accidental concomitant.] If it be its very essence to set itself in motion, it will not be merely in an incidental sense that motion will belong to it, as is for instance the case with the movement of white colour or three cubits length. These last are moved indeed, but they are so simply incidentally, in so far as the body in which they inhere is moved; and thus space is no attribute connected with them. Such space however will be an attribute of the soul if it be the case that the soul participates in movement by its very nature.

Further, if the soul be in motion by its inherent nature, it should also admit of being put in motion by external force: and supposing it to be moved by force, it should also admit of being moved by nature. So also is it with respect to rest: for when an object is moved by nature into some state or other, it also rests in this by nature, just as when an object is moved into any state by external force it also rests in this state by force. But even the most vivid imagination will find a difficulty in explaining what would be the character of the forced movements and reposes of the soul.

Again, if the movement of the soul be upward it will be composed of fire, if downward, of earth; such being the directions in which these bodies naturally move. And the same holds good also of the intermediate elements.

But fourthly, since the soul according to all appearance sets the body in motion, we may reasonably suppose that it originates in the body the same movements as those by which it is itself in movement. But if this be so, then it follows by conversion that whatever be the movement with which the body is moved, such also is that with which the soul itself is moved. Now the movement of the body is a local movement. It follows therefore that the soul would also change its position in respect of the body, executing these changes either in its entirety or in its several parts. But were this possible it would further follow that the soul would be able after passing out of the body to enter it again: and this in turn would involve the absurd conclusion that animals after having died can rise again.

With regard on the other hand to accidental movement, it is true that the soul could be thus moved incidentally at the hand of something else: the animal in which the soul is contained may be pushed on by external force: and so the soul would be indirectly put in motion. But if a thing is essentially put in motion of itself, it must not be supposed put in motion by something else (unless in an indirect sense), just as the self-subsisting good should not be the good pursued for other ends nor the good absolute become the good relative. And yet about the only thing by which the soul, supposing it is moved, could be said to be so, would be the objects of sense.

If on the other hand it be said that the soul sets itself in motion in and by itself alone, it follows that it would also be moved in and by itself. But all movement is a displacement of the moved qua moved: and therefore the soul would be displaced and taken out of its essential nature, if it be pot merely incidentally that it sets itself in motion. This however is the reverse of our hypothesis which holds that the motion is an attribute of its essential nature in and by itself

A further modification of this theory is found in the view of those who say that the soul moves the body which contains it in a manner corresponding to that in which the soul itself is moved. This view is held by Democritus, whose words rather recall the saying of Philippus the comedian, that Daedalus made his wooden Aphrodite capable of movement by pouring quicksilver into her. Democritus' explanation is in truth not much superior to this. He tells us that the atomic globules contract and move the whole body in virtue of the law imposed upon them never to remain at rest. But, we should ask, are these same elements to produce rest also. How they will produce this result it is difficult or in fact impossible to say. And indeed generally, apart from any special form of this doctrine, the soul, so far as we can see, moves the body not in this manner but through the agency of purpose and of thought.

The Timaeus similarly explains on physiological principles the manner in which the soul moves the body: reasoning that the soul by the fact that it is itself in motion moves the body also, in consequence of its intricate conjunction with it. The writer regards the soul as compounded of the different elements and distributed according to the harmonic numbers [which underlie the universe] in order that it might have an original inborn perception of harmony and altogether be borne in harmonious courses. The soul so compounded, he bent the straight line [of the numbers] round into a circle, and when out of the one circle he had cut two circles connected at two points, he again divided the one circle into seven circles, considering as he did the revolutions of the heaven to correspond with the movements of the soul.

The first objection to this theory is that it is not befitting to speak of the soul as a magnitude, at the same time as the soul of the universe is evidently intended to be some such thing as is the so-called reason: it cannot at least be something like the sensitive or appetitive soul which is so described, as their movement is not circular rotation. Reason however is, no doubt, marked by unity and continuity, but it is so only in the sense in which the action of thought is so also. Now the action of thought is equivalent to the objects of thought; and these, it is true, form by their sequence a unity, but it is the unity of a number and not of a geometrical body. Hence then neither is the reason continuous in this sense but it is either destitute of parts or it is not continuous as a magnitude. How, in fact, if it be a magnitude, is it to think . Is it to do so as a whole or only with some one of its parts? If it be with the parts, it must be either as a magnitude or as a point if we may call this last a part. /If, however, it be as a point, then, as the number of points in a given magnitude is endless, the process of thought will never reach an end; if it be as a magnitude it will think the same thing frequently or without limit. But, as matter of observation, thought may be exercised once for all.

Besides if it be sufficient for the soul to have touched with any of its parts, what need is there for it to move in a circle or indeed to have magnitude at all? If, on the other hand, it be necessary for thought that it should touch with the whole circle of the soul, what will happen when it touches with the parts? How further is it to think that which has parts through that which is without parts, or that which is without parts by that which has parts? And yet (from the standpoint of the Timaeus) reason must be a circle of this material kind: for thinking must be the movement of reason just as revolving is that of a circle: so that if thinking be a process of revolving it follows that reason would be the circle of which such a revolution constitutes thought. And again the soul will be continually involved in thought, since (as is asserted in the Timaeus) circular movement is everlasting. [This however is opposed to all experience:] in the case of processes of thought leading to action there are certain ends which limit them, all being for the sake of something else, and thoughts applied to speculation only are limited in the same manner as the reasoned explanations which they involve. Now every explanation resolves itself into either a definition or a deductive demonstration. But as for demonstrations, they both start from a principle as a beginning and have as it were a termination in the syllogism or the conclusion; and even if they do not reach a termination, still they do not turn back again to the beginning, but, employing always a fresh middle term and an extreme, proceed forward in a straight line, whereas a circular movement always returns back Xo the beginning. The same thing holds good also of definitions: they are all limited and determined. Besides, if the same revolution takes place a great many times, it will be necessary to think the same thing frequently. Further, thought bears a greater similarity to rest and stoppage than to motion: and so also is it likewise with syllogism.

Happiness, again, cannot be an attribute of that which is acted on by force and does not happen with ease: and if, to obviate this difficulty, it be held that movement does not constitute the soul's essential nature, its movement would be contrary to nature. It is burdensome also for the soul to be united with the body without possibility of release from it: and not only so, but such union is even something which is to be if possible avoided, supposing it to be better for the reason to be independent of the body, as is usually said and widely believed.

There is an obscurity also as to the reason why the heavens are carried in a circle; for it is not the essential nature of the soul which is the reason of its being carried in a circle, this movement being merely incidental to it: nor is it the body which is the cause, the soul being rather the cause which produces movement in the body. Nor indeed is it asserted that the soul moves in this manner because it is its better course.

God however must have made the soul to be moved in this circular fashion for no other reason than that it was better for it to be in movement than to remain at rest, and, further, better to be moved in this manner than in any other. Such an investigation however can be more appropriately discussed in other fields of study, and may be therefore for the present left aside.

There is however one peculiar inconsistency which we may note as marking this and most other psychological theories. They place the soul in the body and attach it to the body without trying in addition to determine the reason why or the condition of the body under which such attachment is produced. This would seem however to be a real question calling for solution: in so far as it is by reason of this communion that the one factor is active the other passive, and that the one sets in motion the other is in motion: and relations of this kind are never found in cases of mere juxtaposition. The thinkers however to whom we are referring attempt to state the nature of the soul only: with regard to the nature of the body which is to receive the soul they determine nothing in particular. And thus, although every body seems to possess a distinctive form and character, they act as if it were possible for any soul to clothe itself in any body, after the manner of the tales which Pythagoreans tell of transmigration. Their account in fact is much like speaking of the carpenter's art as clothing itself in flutes: the truth being that just as art makes use of its appropriate instruments, so the soul must make use of its fitting body.


There is still another opinion handed down respecting soul which meets with acceptance at the hands of many no less than any of the views which have been stated, though even in popularly written treatises it has been examined and brought, as it were, to account for its assumptions. The soul is by the doctrine in question regarded as a harmony of some sort. A harmony, it is argued, is a blending and conjunction of opposites: and it is out of opposites that the body is composed.

Harmony however it may be objected (i) is either a certain ratio of composition or an adjustment of bodies: and the soul cannot be described by either of these terms. Besides (2) movement is not a property which can be predicated of a harmony: while it is by almost all thinkers attributed to the soul. Harmony again (3) is a term which may be applied to health and to the bodily excellencies in general with much more propriety than to the soul: as would be (4) very evident if we should attempt to explain the feelings and functions of the soul by resolving them into some special harmony: so difficult is it to make them correspond. It may be added further (5) that in speaking of a harmony we do so with reference to two points. In the strictest sense, the term denotes so closely fitting an adjustment on the part of bodies possessed of movement and position as lets in nothing homogeneous; and hence secondly it is applied also to the ratio which holds between things that are compounded.

In neither of these two senses can the soul be reasonably regarded as a harmony. The adjustment of the parts of the body is very easy to be discovered: there are many such adjustments and they can be effected in a great variety of manners. Of what part then, we may ask, are we to suppose the reason is an adjustment or how are we to suppose it to be effected? or, again, what adjustment is it that forms the sentient or the appetitive nature? It is equally absurd' to regard the soul as the expression of the ratio of the composition. The composition of the elements forming flesh is subject to a different ratio or proportion from that which forms bone; and if the soul be merely this ratio of composition then it will follow that we have many souls spread over the whole body, because all the parts of the body are formed from elements combined together and ex hypothesi it is the ratio regulating their composition which constitutes a harmony and therefore soul. This too suggests a question we might put to Empedocles relatively to his statement that each of the bodily parts is determined by a certain ratio. Whether, we might ask, is the soul this ratio, or is it something else which is implanted in the members? And further does the principle of 'love' give rise to any composition whatsoever or only to that standing in a certain ratio; and if the latter, is this love the ratio itself or is it something else outside the ratio?

Difficulties then of this kind may be raised upon the supposition that soul is a harmony. At the same time, if the soul be something different from the composition of the bodily parts,, the question rises, how comes it that the soul is annihilated when the flesh and the other parts of the animal organism are destroyed — and further, if, after giving up the view which regards soul as the ratio of the composition, it can no longer be maintained that each of the parts of the body possesses a soul, it is difficult to see what it is that is destroyed when the soul has taken its departure.

It is evident then from what has been said that the soul cannot be a harmony: and further that it cannot have a circular movement. It may however, as we have said, be moved and move itself incidentally, so far as that in which it is contained may be moved, and this itself moved by the soul: otherwise, it is impossible for it to exhibit local movement.

A more plausible standpoint, however, from which to raise doubts in support of the movement of the soul might be found in an appeal to the fact that the soul is (as we say) pained, takes joy, shews confidence, is exposed to fear, and further is angered and perceives and pursues inferences — all such operations being viewed as processes of movement. Hence then it might be supposed the soul itself is moved. This, however, need not be the case. It may be indeed that feeling pain or rejoicing or exercising thought are motions in the fullest sense, and each of them may be identical with being moved. Further, too, this movement may be effected by the soul — for example, feeling anger or fear may be the result of such and such a movement of the heart, and inference is either a movement of this sort or something else. Some of these phenomena again may result from local movements, others from qualitative changes in a manner of which the details must be left for further inquiry.

Although, however, all this may be true, we must add that to speak of the soul as feeling angry is no more appropriate than to speak of the soul as weaving or building. Perhaps, in fact, it is better to say not that the soul pities or learns or infers, but rather that the man does so through his soul. Nor in saying that the man carries on these operations through his soul, must we take this to mean that the movement is in the soul, but simply that the movement sometimes advances towards soul, sometimes starts from it. Sense perception, for example, starts from such and such individual things [and advances forward to the soul which reads them]: recollection on the other hand starts from the soul and terminates in the movements or impressions which are stored up in the organs of sense. It must be remembered, too, that reason as a self-contained reality would seem to be implanted within the soul and would not seem to be destroyed with the dissolution of the body. For, if it could be so destroyed, it would be so chiefly in consequence of the decay following in old age, whereas, as facts really stand, the case is perhaps parallel to that of the organs of sense, where we should allow that the old man, if he were to receive an eye fitted for vision, would see as well as the young man. Thus old age is the result not of any affection sustained by the soul but by the medium in which it is contained, just as is also the case in drunkenness and in disease; and thinking and reflection are weakened on the destruction of something internal, but as for thought itself, it is unaffected by such accidents. So also the processes of discursive understanding as also loving and hating are not affections of the reason but of the organism which possesses it, so far as it possesses it. And hence it is that when this vehicle is destroyed, neither recollection nor love are longer possible, because these functions and feelings were not attributes of the reason but of that combination of soul and body which has perished. Reason, however, is in all probability of a diviner character, and not subject to impressions from without.

It is evident then from these considerations that the soul cannot be in motion: and if motion is a predicate of it in no sense whatever, it evidently would not be moved either by itself.

Of all psychological theories the most unreasonable is that which describes soul as a number which sets itself in motion. Such a view involves double impossibilities — firstly those resulting from its movement and more particularly those which spring from speaking of it as a number. In what manner for instance, (1) are we to conceive a unit as moved — and by what means and under what conditions is it to be effected — seeing that it is devoid of parts and contains no differences, while if it be at once fitted to produce movement and also subject to movement it must exhibit points of difference? (2) Further, it is a doctrine of the schools that the line when moved produces a superficies, and the point when moved creates a line. Thus then since the point is merely a unit or monad possessing such and such a situation, and the number of the soul is no doubt somewhere and possesses a certain position, it follows that the movements of monads or units will be lines also [not souls or animate existences]. Besides (3) if we take away a number or unit from a number, it is another and a different number that is left: whereas plants and many animals live after they have been divided and are held to possess specifically the same and not a different soul. Besides (4) there would appear to be no difference between speaking of monads or of infinitely small particles: if points be formed out of the globules of Democritus and quantity- alone remain, still there will be in this as in ever>'thing continuous, something moving on the one hand, something moved on the other; as this law is the result not of any difference in size but rests simply on the ground that the one object as the other is a quantity. Thus then there must be something which will set the monads in motion. But if it be soul which produces movement in the animal, it will be soul which does so also in the number: so that the soul is not at once the moving and the moved, but the moving factor only. How then (5) can soul, being thus the moving factor only, be a monad? Supposing it to be a monad, it must be different from other monads: but what difference can there be between one monadic point and another except position? Thus then (6) if, on the one hand, the monads as also the points of the body are different from one another, still the monads will be in the same space as the latter — because each monad will occupy the room of a point. But if two can be in the same place, what is there to prevent an endless number from being also in the same place? This, however, is absurd; those objects of which the space is indivisible are themselves also indivisible. If, on the other hand, the points in the body constitute the number of the soul, or if the soul be the number arising from the points in the body, why is it that all bodies do not possess a soul: seeing that there seems to be points in all of them even innumerable? And further we may ask, (7) how is it possible for souls to be separated and released from the body, considering at any rjite that lines cannot be resolved into their points?


There are then, as we have said, two consequences of this doctrine of the soul. On the one hand its supporters are brought to maintain a view identical with those who regard soul as some subtle body, while, on the other hand, they are landed in the peculiar absurdity which Democritus fell into in explaining how the body is moved by the soul. For if there be a soul in every sentient body, there must be two bodies within the same body, supposing the mind is a body of some sort or other: those, on the other hand, who say it is a number must either allow many points to exist within one point or else allow every body to possess a soul, unless the number be introduced as differing from other numbers and from the points existing in the body. It follows also that the living creature is moved by number much in the same way as we said Democritus moved it. For what difference does it make whether we speak of the movement of small globes or of large monads or of monads generally in movement. In either case the movement of the animal must be the result of the moving of these elements.

These and many other like consequences meet those who have combined together movement and number into one conception. Such a conception can not only not be the definition of soul: it cannot even be regarded as a concomitant attribute of it. This is evident when we attempt to explain by reference to such a notion the feelings and functions of the soul, as for instance, its ratiocinations, perceptions, pleasures, pains, &c.: as we said before, it is not even easy by the help of the imagination to conjecture from it what would be their character.

Thus then we have gone through the difficulties and objections which may be raised against two of the three methods of defining soul which have been transmitted to us. Some we have seen have regarded it as the most mobile element because it possesses the power of moving itself: others have viewed it as a body of the subtlest and the finest parts or as the most incorporeal of all other bodies. It remains to examine the sense in which it is said to be compounded of the different elements.

The object of this conception of the soul is, say its supporters, to explain how it can perceive the objects of existence and gain knowledge of each individual thing. A number of impossibilities, however, necessarily follow on this doctrine. It assumes, to begin with, that like is known by like, thus identifying, as it were, the soul with the things it knows. Our objects of knowledge however include not only elements but many other things besides, and, what is perhaps still more worthy of notice, the things compounded of these elements are unlimited in number. Now granting that the soul knows and perceives in the way described the elements from which each of these is formed, still, we may ask, by which will it know or perceive the concrete whole, as for example what is God or man or flesh or bone, and similarly any composite object. The different elements do not seem to compose each of these objects in any way whatever but according to a certain ratio and adjustment, as Empedocles himself says with respect to bone.

Then did the earth the productive within the huge furnace primeval

Gain out of eight parts two of the liquid transparently crystal;

Four parts came from the fire; and the bones white came to existence.

Obviously then there is no good in the elements being present in the soul, unless the ratios and the different adaptations be present also; for although each element may recognise its similar, still it will acquire no knowledge of a bone or of a human being.

Unless these be present within it also. It. need hardly be/said however that this is quite impossible: who could question whether such an object as a stone or man is present in the soul? And the same thing may be said of the good and not "'good, as also in other cases.

Being, it may be objected further, is a term used, in various senses: it indicates now concrete substance, now quantity or quality, or it may be some other of the categories as they are distinguished. Is soul then, it may be asked, to be composed of all the categories or not? To the former supposition it may be at once replied that there are no elements which are common to all the categories. Does then, we may ask, the soul consist merely of the elements that fall under the category of ' substance? In that case, how does it come to have knowledge of each also of the other categories? Will it be said that every category of being has its own elements and appropriate principles and that the soul consists of these? The result then will be that the soul will have to be a quantity and quality as well .as a substance. But out of the elements of quantity it is impossible that a substance should be formed: only a quantity can arise from elements of quantity. Such are the difficulties as well as others of a similar character involved in holding that the Soul consists of all the elements.

It is a further inconsistency in the supporters of this doctrine that, while asserting that like perceives like and that we know like by like, they maintain that like is unaffected by like, and at the same time explain perception as a kind of affection and of being moved, and treat thinking and cognition in a similar fashion. There are in. fact many difficulties and perplexities involved in saying with Empedocles that everything is known through the corporeal elements and that the similar is apprehended by the similar — as is especially attested by the fact that all those parts within the bodies of animals, which are composed of earth simply-^as for example bones, sinews, hairs — are held to perceive nothing and thus not even those things which are like them^-although according to the theory they should.

It maybe added further that each one of the elemental principles will have much more ignorance than understanding: because while each element will know some individual object, it will be ignorant of many; as in fact it will be ignorant of everything else outside this one. Nay in fact Empedocles has to face the conclusion that God is most destitute of understanding: for he alone will have no knowledge of one among the elements — viz. strife, although all things mortal will possess this, because they are each compounded out of all the elements.

There is, besides, a general inconsistency which may be brought against the theory. Why is it on this supposition that all objects of existence do not possess a soul? Every one of them is either an element or formed from some one element or from several or all of them; and such objects must necessarily know one thing or some or all.

The question might besides be raised, what is it that brings the elements to unity? The elements themselves resemble mere unformed matter, and it is the synthetic force, whatever it may be, which is most important Now it is impossible that there should be anything superior to soul or dominating it: and still more impossible that there should be anything superior to reason: for reason, it is to be believed, is by nature first born and supreme. And yet the philosophers in question make the elements the first forms of existence.

A general objection which may be brought both against those who, because the soul perceives and knows things existing, describe it as formed from the elements, and also against those who make it the most mobile principle, is that their statement does not apply to every form of soul. Sentient beings are not in every case capable of movement: some animals in fact appear to be stationary in place: although at the same time this is thought to be the only form of movement by which soul 'moves' the animal. A like objection falls on those who construct reason and the faculty of sense out of the elements: for plants [of which their theory takes no account, although compounded of the elements] appear to live without partaking in locomotion or sensation, and there are many animals which appear to have no powers of discursive reasoning. But even if this be granted and reason as well as the faculty of sense regarded as parts only of the soul, not even then should we have a general statement made respecting every soul or even respecting the whole of one particular form of it.

A like defect meets us in the account given in the verses ascribed to Orpheus. The soul, it is there said, enters from the universe, being carried inwards by the winds as animals are breathing. Now this is impossible in the case of plants and also in the case of certain animals in so far as they are not known to breathe: but this the holders of this theory have failed to notice. But though it be necessary to construct the soul out of the elements, there is no necessity to compose it out of all of them: one or the other of two contraries is sufficient to distinguish at once itself and its opposite. Thus by means of the straight we judge both the straight line and the crooked, the rule being the standard of both, while the crooked on the other hand can act as standard neither to itself nor to its opposite the straight

A general diffusion throughout the universe is claimed by some writers for the soul: it was in fact possibly this view which led Thales to assert that everything was full of Gods. This however is a theory which presents some difficulties. Why is it, for instance, that the soul which is in the air or in the fire does not produce an animal organism, while it does so in those objects which are mixed and compound, and this too though such thinkers hold the soul dispersed within the former to be the superior? With reference to which, we might further ask why it is that the soul in air is, as they hold, more excellent and more immortal than that amongst animals. In two ways, in fact, their theory is inconsistent with itself and paradoxical. To speak of fire or air as of an animal is rather paradoxical: to hold, on the other hand, that soul is present in them and yet not call them animals is inconsistent. So again, the ground on which they conceive soul to be present in these elements is the opinion that the whole is homogeneous with its parts: and thus it is incumbent on them to say that the soul is of like kind with its parts, if it be by acquiring part of their environment that animals become possessed of soul. If however the air when divided remains of one uniform kind, whereas the soul is (as they maintain) of different kinds, it is clear that some part of it will, some other will not, be present Either then the soul of living creatures must be throughout homogeneous, or soul cannot exist in every elemental part of the universe.

It is clear then from what has been said, that neither does cognition attach to the soul in consequence of its being composed of elements, nor can it be said with any appropriateness or truth that it is moved. Knowledge however is a property of the soul, and so also is perception and opinion, and further appetite and volition and desire in general: and it is by the agency of the soul that animals possess local movement and powers of growth, and reach their full development and final dissolution.

The question therefore rises, whether it is to the whole of the soul that each of these belongs, and whether we think and perceive and in general perform each of our functions, active and passive, with the whole of it, or, on the contrary, do we perform different functions with different parts. And as for life likewise we must ask whether it is contained in some one of these parts or in several of them, or whether it may be even in all of them, or whether it is something else which is its cause.

There are indeed some thinkers, who assert that the soul is divided into parts, and that it reasons with one part, desires with another part. But what, we may then ask, is it, if the soul be originally and naturally divided — what is it that holds the soul together? It cannot certainly be the body: on the contrary, the soul would generally be said to unite the body; at least when the soul has made its exit from it, the body is dissolved and rots. If then it be something else that makes it one, this something else could only be the soul; and as to that something else it will be needful in turn to inquire, whether it is one or made of many parts. If it be one, why should not the soul be this unity at once? if divided, reason will again inquire what it is that binds it together: and so the process will go on for ever.

Questions might be raised also about the different parts of soul, and we might ask what power is it that each exercises in the body: for if the soul as one whole unites the body as a whole, it is probable that each also of the parts unites and binds some portion of the body. This however seems impossible: it is difficult even to imagine what part reason will connect, or in what manner it will do so. Plants furthermore are found to live after they have been divided, and so also among animals are some insects — a fact implying that their different parts possess a soul which, if not numerically one, is still specifically the same: each at any rate of the separate parts possesses sensation, and displays a power of local movement for some time. That they do not continue to do so, is no matter for surprise, because the parts in question do not possess such organs as will maintain their nature. None the less, all the parts of soul are present in each one of these parts, and they are homogeneous with one another and with the soul taken as a whole, standing to one another as inseparable but to the whole soul as though it were divisible. Further also, the principle of life in plants seems to be a kind of soul: for this alone is common at once to animals and plants, and while it can itself exist separate from the principle of sense, there is still no living object that can possess sensitive capacities without having this capacity of growth which plants display.


The psychological theories of earlier thinkers have occupied us hitherto. We will now take up the subject as it were afresh, and attempt to determine what soul is, and what is the most comprehensive definition that can be given of it.

Real substance is the name which we assign one class of existing things; and this real substance may be viewed from several aspects, either, firstly y as matter, meaning by matter that which in itself is not any individual thing; or secondly y as form and specific characteristic in virtue of which an object comes to be described as such and such an individual; or thirdly^ as the result produced by a combination of this matter and this form. Further, while matter is merely potential existence, the form is perfect realization (a conception which may be taken in two forms, either as resembling knowledge possessed or as corresponding to observation in active exercise).

These real substances again are thought to correspond for the most part with bodies, and more particularly with natural bodies, because these latter are the source from which other bodies are formed. Now among such natural bodies, some have, others do not have life, meaning here by life the process of nutrition, increase and decay from an internal principle. Thus every natural body possessed of life would be a real substance, and a substance which we may describe as composite.

Since then the body, as possessed of life, is of this compound character, the body itself would not constitute the soul: for body is not [like life and soul] something attributed to a subject; it rather acts as the underlying subject and the material basis. Thus then the soul must necessarily be a real substance, as the form which determines a natural body possessed potentially of life. The reality however of an object is contained in its perfect realization. Soul therefore will be a perfect realization of a body such as has been described. Perfect realization however is a word used in two senses: it may be understood either as an implicit state corresponding to knowledge as possessed, or as an explicitly exercised process corresponding to active observation. Here, in reference to soul, it must evidently be understood in the former of these two senses: for the soul is present with us as much while we are asleep as while we are awake; and while waking resembles active observation, sleep resembles the implicit though not exercised possession of knowledge. Now in reference to the same subject, it is the implicit knowledge of scientific principles which stands prior. Soul therefore is the earlier or implicit perfect realization of a natural body possessed potentially of life.

Such potential life belongs to everything which is possessed of organs. Organs however, we must remember, is a name that applies also to the parts of plants, except that they are altogether uncompounded. Thus the leaf is the protection of the pericarp and the pericarp of the fruit; while the roots are analogous to the mouth in animals, both being used to absorb nourishment. Thus then, if we be required to frame some one common definition, which will apply to every form of soul, it would be that soul is the earlier perfect realization of a natural organic body.

The definition we have just given should make it evident that we must no more ask whether the soul and the body are one, than ask whether the wax and the figure impressed upon it are one, or generally inquire whether the material and that of which it is the material are one; for though unity and being are used in a variety of senses, their most distinctive sense is that of perfect realization.

A general account has thus been given of the nature of the soul: it is, we have seen, a real substance which expresses an idea. Such a substance is the manifestation of the inner meaning of such and such a body. Suppose, for example, that an instrument such as an axe were a natural body: then its aixehood or its being an axe would constitute its essential nature or reality, and thus, so to speak, its soul; because were this axehood taken away from it, it would be no longer an axe, except in so far as It might still be called by this same name. The object in question, however, is as matter of fact only an axe; soul being not the idea and the manifestation of the meaning of a body of this kind, but of a natural body possessing within itself a cause of movement and of rest

The theory just stated should be viewed also in reference to the separate bodily parts. If, for example, the eye were possessed of life, vision would be its soul: because vision is the reality which expresses the idea of the eye. The eye itself, on the other hand, is merely the material substratum for vision: and when this power of vision fails, it no longer remains an eye, except in so far as it is still called by the same name, just in the same way as an eye carved in stone or delineated in painting is also so described. Now what holds good of the part must be applied to the living body taken as a whole: for perception as a whole stands to the whole sensitive body, as such, in the same ratio as the particular exercise of sense stands to a single organ of sense.

The part of our definition which speaks of something as " potentially possessed of life " must be taken to mean not that which has thrown off its soul, but rather that which has it: the seed and the fruit is such and such a body potentially. In the same way then as cutting is the full realization of an axe, or actual seeing the realization of the eye, so also waking may be said to be the full realization of the body: but it is in the sense in which vision is not only the exercise but also the implicit capacity of the eye that soul is the true realization of the body. The body on the other hand is merely the material to which soul gives reality: and just as the eye is both the pupil and its vision, so also the living animal is at once the soul and body in connection.

It is not then difficult to see that soul or certain parts of it (if it naturally admit of partition) cannot be separated from the body: for in some cases the soul is the realization of the parts of body themselves. It is however perfectly conceivable that there may be some parts of it which are separable and this because they are not the expression or realization of any particular body. And indeed it is further matter of doubt whether soul as the perfect realization of the body may not stand to it in the same separable relation as a sailor to his boat

This much may suffice as a description and sketch of the nature of the soul.


It is however by proceeding from that which in the order of nature is indistinct, but is relatively to us more obvious and manifest, that we reach what is clear and more intelligible in the order of thought. We must therefore make a fresh attempt to discuss soul in this manner. For a definition should not, as most definitions do, merely assert the existence of an object and say what it is: it should also contain and express the cause or reason of the object. But, as usually framed, the terms of definitions are merely like conclusions. Thus, for example, let us ask — What is squaring? Squaring, it will be answered, is the construction of a rectangular equilateral figure equal to another figure with unequal sides. Now such a definition is merely like the statement of a conclusion. To say, on the other hand, that squaring is the discovery of a mean proportional is to state the cause which explains the result

It may serve as a fresh beginning for our inquiry to say that the animate is distinguished from the inanimate or soulless by the fact of life. There are a number of ways in which a thing is said to live; yet should it possess only one of them — as for example, reason, sense — perception, local movement and rest, and further movement in respect of nutrition as well as of decay and growth — we say it lives. Hence it is that all plants are thought to live; because they manifestly contain within themselves such a power and principle as enables them to acquire growth and undergo decay in opposite directions; for they do not while growing upwards not grow downwards but they grow in both directions and on all sides, and they continue to live so long as they can assimilate nourishment Now this faculty of nutrition may be separated from the other functions; but in the case of mortal creatures the other faculties cannot exist apart from this, as indeed is evident from plants which possess no other psychic power except this faculty of growth.

It is then through this principle of nutrition that life is an attribute of all living things. At the same time the animal strictly so called only begins when we reach sensation: for even those objects which do not move themselves nor change their position but possess sensation are said to be animals and not merely to be living. Among the senses themselves, it is touch which is the fundamental attribute of all animal forms. And just as the nutritive function may exist apart from touch and every form of sense, so also may touch exist without any of the other senses. Thus while nutritive is the name given to that part of the soul in which plants share as Well as animals, all animals are found to possess the sense of touch. Why each of these faculties is so allotted we shall state hereafter: here it may be enough to say that the soul is the source and Centre of the various states here mentioned and is determined and defined by those powers of nutrition, sensation, understanding and movement.

With regard to these several functions, whether each is the soul or a part of the soul; and if a part, whether so as only to be separable in thought or actually in space — with regard to some of these questions it is not difficult to see the answer, while others present difficulties. For just as, in the case of plants, some parts when divided are found to live even when separated from one another — a fact which seems to shew that the soul within them exists as actually one though it is potentially several; so also do we see it happen with respect to another specific aspect of the soul in the case of insects which have been divided. In such a case, each of the divided parts possesses sensation and the power of local movement, and if sensation, then also in addition imagination and desire: for where sense is present, there pain and pleasure follow also as concomitants, and where pain and pleasure exist, appetite is also necessarily present. With regard on the other hand to reason and the faculty of thought we have as yet no obvious facts to appeal to. Reason however would seem to constitute a different phase of soul from those we have already noticed and it alone admits of separation as the eternal from the perishable. But as for the other parts of soul, it is clear from these considerations that they are not separated in the way that some maintain. At the same time it is evident that in thought and by abstraction they may be divided from one another. The sensitivity is one thing, the reflective faculty another, if it be one thing to have sensation, another thing to exercise reflection. And this same truth holds good also of the other powers which have been described.

Respecting these various powers, there are some animals which possess them all, others which have merely some of them, and others again which have but one only. It is this which makes the difference between one class of animals and another, though the reason for this fact can only be investigated afterwards. The same thing may be noticed also as regards the senses. Some animals have all of them, others have but some, and a third class possesses only that one sense which is most indispensable — viz. touch.

[Life, then, and sensation are what mark the animate.] But there are two ways in which we may speak of that by which we live and have sensation just as also that by which we know may be employed to denote either knowledge or the mind, by both of which we are in the habit of speaking of people as knowing. So also that by which we are in health denotes on the one hand the health itself, on the other hand some portion of the body or it may be the whole of it. Now of these two uses, knowledge and health are what we may term the determining form and notion and so to speak the realization of the recipient faculty, in the one case of knowledge, in the other of health — for the passive material which is subject to modification is what is taken to be the home of the manifestation of the active forces. Soul then is the original and fundamental ground of all our life, of our sensation and of our reasoning. It follows therefore that the soul must be regarded as a sort of form and idea, rather than as matter and as underlying subject. For the term real substance is, as we have before remarked, employed in three senses: it may denote either the specific form, or the material substratum, or thirdly the combination of the two: and of these different aspects of reality the matter or substratum is but the potential ground, whereas the form is the perfect realization. Since then it is the product of the two that is animate, it cannot be that the body is the full realization or expression of the soul; rather on the contrary it is the soul which is the full realization of some body.

This fact fully supports the view of those who hold that the soul is not independent of some sort of body and yet not to be identified with a body of any sort whatever. The truth is that soul is not body but it is something which belongs to body. And hence further it exists in a body and in a body of such and such a nature, not left undetermined in the way that earlier thinkers introduced it into the body without determining besides what and what sort of body it was, although it does not even look as though any casual thing admitted any other casual thing.

This same conclusion may be reached also on a priori grounds. The full realization of each object is naturally reached only within that which is potentially existent and within that material substratum which is appropriate to it. It is clear then from these considerations that soul is a kind of full realization or expression of the idea of that which has potentially the power to be of such a character.


Of the powers of soul which have been mentioned, some organisms, as has been said, possess all, others again a few, while a third class possesses one only. The powers in question are those of nutrition, of sensation, of desire, of local movement and of reasoning. Plants possess the function of nutrition only: other creatures have this and also the faculty of sensation; and if this latter, then they must also have the faculty of desire: for desire includes appetite and passion and wish. Animals however without exception possess one at least among the senses — viz. touch: and wherever a faculty of sense is present it is accompanied by a feeling of pleasure and pain, and an object which is pleasant or painful. But where these are present, there appetite is also: for appetite is the desire of what is pleasant.

Besides, all animals have a sense for nourishment — viz. touch — for it is by means of things dry and moist, hot and cold, that all animals are fed: and touch is the sense which directly perceives these. As for the objects of other senses, on the contrary it is only incidentally that they are fed by them; for neither sound nor colour nor smell directly contribute to food. Flavour again is included under the class of things that are tangible. Now hunger and thirst, which attach to taste, are forms of appetite, hunger being concerned with what is hot and dry, thirst with what is cold and moist, while flavour is as it were their seasoning. These subjects we must afterwards discuss with more detail. Meanwhile it need only be asserted that those animals which possess the sense of touch have also the attribute of desire. Whether in addition they possess imagination is an obscure subject which must be investigated afterwards. Some animals possess, beside such faculties, the power of local movement also: others, as for instance men or other beings similar or superior to them, if there be any such, possess also understanding and reason.

It is clear then that there is one general definition of soul neither more nor less than there is one definition of figure. Just as in the latter case there is no figure other than the triangle and the figures which follow on it, so neither in the case of soul is there any form of it beyond those which we have enumerated. No doubt it is possible to have in reference to figures a common definition which will suit all figures and yet be peculiarly characteristic of no one figure in particular, and a like general definition is possible also with respect to the forms of soul which we have named. [But such common definitions are mere abstractions.] And hence it is absurd both in this case and in others to seek for a universal definition which shall be peculiar to no one form of existence nor framed with reference to the particular and individual species, if such common definition makes us neglect particular analysis.

The different forms of soul in fact stand to one another in the same way as do the several species of figure: both in the case of figures and of animate beings, the earlier form always exists potentially in the later. Thus the triangle is contained within the square and similarly in the faculty of sense the function of nutrition is implicitly contained. Thus we must push our inquiry into particulars and ask what is the soul of each form of existence; as for example what is that of a plant or of a man or of some brute beast. We must inquire also why they stand in such an order of succession. The sensitive nature, for instance, is not found without the nutritive: and yet the nutritive is found separated from the sensitive, as in the case of plants. Without the sense of touch, again, none of the other senses is present, while touch itself is found apart from the others: many animals possessing neither sight nor hearing nor the sense of smell. So likewise animals possessed of the faculties of sense sometimes have, sometimes do not have, the faculty of local movement; while finally the smallest class possess also reflection and understanding. And all mortals that possess the faculty of reasoning possess also all the other powers, whereas those that possess each of those others do not in every case possess reflection; some in fact do not even possess imagination while others live by the aid of this alone. As regards the speculative reason a different account must be given. Meanwhile it is clear that the special definition of each of these powers separately is at the same time the most appropriate account of the soul.


The investigation of the faculties of the soul demands that we should discover what each of them is and then proceed similarly to consider allied and remaining questions. In order however to state the nature of each of them, as for example the faculty of thought or sense or of nutrition, we must beforehand explain what is thinking and what is the act of perception: for viewed in the light of their essential notion the actions which give expression to a power are prior to the power itself. And if this be so, and it be necessary to consider even before the actions their objects, it will, for the same reason, be our first duty to settle about them, as for instance about food and the object of sense and the object of thought.

Food and generation should therefore be the first subjects of our inquiry: for the nutritive faculty is an attribute of other beings as well as man and is that primary and most common function of the soul in virtue of which life is an attribute of all animals. Its office is to generate and to make use of sustenance. In animals in fact that are perfect and not impaired by any defect or that are not created by spontaneous generation the most natural function is to create another like itself, animal thus producing animal, plant plant, so that they may as far as possible partake of the eternal and divine: for this desire is universal and constitutes the end of all natural action — 'end,' it should be remembered, meaning not only the person for which but also the purpose at which something is directed. Since then it is impossible to share in the eternal and the divine in the same identical person, because nothing mortal can remain numerically the same and individual, each individual shares in this in the way it can, in some cases to a greater, in others to a less degree, and though not actually the same it continues as it were the same, because, though not one numerically, it continues one specifically.

The soul then is the cause and basis of the body as alive; and is so in each of the three senses in which the word cause is used: that is to say it is so both as the efficient cause from which movement springs, as the end or final cause and as the real or essential substance of animate bodies.

That the soul is so as essential substance is evident. In the case of all objects, the cause of their existence constitutes their essential substance. Now it is life which constitutes the existence of all animals, and of these processes of life soul is at once the cause and origin; and further, in the case of something which exists potentially, it is the full realization which is the notion or essential nature.

It is equally clear that soul is cause in the sense of end or final cause. Like reason, nature acts for the sake of some object; and this object is its end. Now in the animal world the soul is naturally something of this character. All natural bodies are instruments of the soul: and just as it is with the bodies of animals so also is it with those of plants, all being there simply for the sake of soul. But in saying that the soul is the end or final cause, we must remember that the word *end' is used in two senses, and must understand it as meaning that at which a thing aims quite as much as that for which it exists.

Lastly, the soul is also cause as being the original source of local movement, a faculty however which all creatures do not have. The soul also exhibits phenomena of alteration and augmentation: for sensation is held to be a form of alteration and nothing possesses this faculty of sense unless it participate in soul. So also is it with augmentation and decay: nothing decays or grows in a natural manner except it receive nutrition: and nothing is nurtured except it partake of life.

This is a subject in which Empedocles has not expressed himself correctly. He maintains that the growth of plants when they strike their roots downwards is due to the fact that the earth [of which they are composed] is by a natural law carried in this direction: while their growth upwards is caused by the fact that their other element, the fire, is borne in this direction. Here Empedocles takes neither 'up' nor 'down' correctly. The 'up' and the 'down’ are not the same for all individual objects as for the universe: the head for instance among animals corresponds to the roots in plants, if it be their functions that should determine organs as same and different. Besides, the question rises, what is it that combines elements such as fire and earth when carried in opposite directions. They will be pulled asunder, if there be not something to prevent it, and if there be, then this something is the soul and the cause of growth and nourishment.

There are some who hold that fire alone is the cause of nutrition and growth: because it is evidently the only one among bodies or elements that feeds and increases itself: and hence it might be thought to be the agent for effecting this in plants and animals. Now fire is in a way the concomitant and condition of growth: it is not however absolutely and by itself the cause: rather it is the soul which is so. The increase of fire proceeds without any limit, so long as there is material to burn: whereas in the case of all natural organisms there is an idea which determines their magnitude and increase: and this belongs to the soul and not to the fire, to the ideal form rather than to the indeterminate matter.

As the same faculty of soul is at once nutrient and generative, it is necessary in the first place to determine the nature of nutriment: for it is by nutrition that this faculty is distinguished from the other powers. Nutrition then is thought to consist in the absorption of the opposite by the opposite. This however need not be taken to mean that every opposite is nurtured by every other, but is meant to be applied only to all those opposites that derive not only their origin, but also their increase from one another: for there are many things that originate from one another, e. g. health from sickness, but the change does not always take the form of a quantitative increase. But it appears that not even do such quantitative contraries act as nutriment to one another in the same manner: liquid, for example, serves as nutriment to fire: but fire does not conversely serve as nutriment to liquid. And indeed it seems to be especially in the case of simple bodies that the contraries stand to one another in the relation of nourishment and nourished. Here, however, a difficulty meets us. There are some who on the one hand maintain that like is nurtured by the like, just as the like is increased by the like: while others, as we have said, hold on the other hand that the contrary is so by the contrary, because (they say) the like cannot be affected by the like. The nutriment, they maintain, changes and suffers digestion, and change, they add, always tends towards the opposite or the intermediate. And besides, they argue, the nutriment is affected to some extent by the object which it nurtures, while this is not altered by the nutriment, just as the artisan is not affected by the material on which he operates but this material on the contrary' by the artist: the workman only transforming it from inertness into actuality.

The real question here is what is to be regarded as the nutriment: and whether nutriment is to be taken as it ultimately reaches the system or in its first form is a matter that is disputed. If it be allowed to be both, but be in the one case digested, in the other case undigested, it might be possible to describe nutriment in terms of both the theories which have been enunciated. So far in fact as the food is undigested, the contrary is nurtured by the contrary: so far as it is digested, the like is nurtured by the like. Evidently then there is a mixture of truth and error in the two views. But as nothing can be fed and nurtured except it participate in life, it is the animate body as such that receives nutriment: and thus nutriment is relative to an animate being and is essentially determined by such relation.

There is however a difference between the import of nutriment and that of growth. So far as the animate body is something quantitative, it admits of growth, so far as it is a definite individual substance, it requires nutriment. The food in other words preserves the substance and continues to operate so long as this substance is nurtured: and it produces the generation not of tlie object nourished but of something else resembling it: for the object nourished already exists as a substance, and nothing generates itself but only maintains its own existence.

Thus then this rudimentary psychic form as we have described it, is a power adapted for preserving that which possesses this psychic form in so far as it possesses it: and nutriment enables it to act, so that when deprived of nutriment it is unable to exist. Three elements have here then to be recognized: first, the object nourished; secondly, that with which it is nourished: and thirdly, the power so nourishing it. Of these the last mentioned is the rudimentary or primary soul: the object nourished is the body which contains this soul, while that with which it is nourished is nutriment (Everything however should be named in reference to the end it realizes, and since the end of this function of the soul is to produce another like itself, the first and rudimentary form of soul would be the generative — generative, that is, of another like itself) That by which the nutriment is effected is twofold, just as likewise that by which we steer a ship may denote either the hand or the rudder — the one of which is at once moving and moved, the other moving only. Further it is necessary that all nutriment should be able to be digested, and this digestion is produced by heat: and thus everything animate possesses heat.

A sketch has thus been given of the nature of nutriment: it will be necessary however to examine the subject with more detail in the treatise appropriate to it


The character of sense-perception as a whole is the next subject which it falls to us to discuss. And perception, it was said, takes place as a result of being moved and being impressed: common opinion in fact views it as a sort of qualitative change or alteration. Now it is a doctrine held by some that in an impression like is affected by like. How far this is possible or impossible we have stated in our general discussion on the subject of the active and the passive processes. It suggests however at once the question — why is there no perception or sense of the senses themselves, and why do the senses not produce a perception without the help of external objects, when there is contained within them fire and earth and the other elements which are objects of perception either in themselves or in virtue of their properties. Evidently, it follows, the power of sense perception exists not as something actually exercised, but only as something potential. And so the case is parallel to that of combustible material, which is not burnt by itself without the presence of that which can set it on fire: otherwise it would set fire to itself, and there would be no need for the help of actual fire. We must note however that we use the word 'perceive’ in two senses. In the case of that which has the power to hear and see, we say it hears and sees, even if it chance to be asleep, just as much as we do in the case of that which is already actually at work. Perception therefore would be similarly used in two senses, on the one hand as in potentiality, on the other hand as in actuality: and this same distinction will in turn apply to the object of perception, which is from one aspect potential, from another actual.

Let us then in the first place agree to regard in our discussion the words "passive impression" "movement" and "activity" as identical: for movement is a species of realized activity, though, as has been elsewhere said, it is imperfect. Now in every instance things are impressed and set in movement by something which is capable of producing an impression and which exists in full activity. And thus an impression is in one sense made by the like, in another sense by the unlike, as has been already said; for it is as unlike that anything suffers an impression: after the impression has been made, it is converted into like.

But, in the second place, a distinction must be drawn with reference to potentiality and actuality; at present we are speaking about them as if they admitted of no variations of meaning. For instance any individual may be described as knowing (1) in the sense in which we should describe a man as knowing, because, i.e., man is included in the class of beings that are intelligent and gifted with knowledge; or (2) an individual might be said to know in the sense in which we speak of a person as knowing

only after he has acquired a knowledge of the principles of grammar. Now of these two persons, each possesses the capacity for knowledge in a different sense — the one because the generic character and fundamental nature of man is of this description, the other because if he wished he would be able to apply his knowledge, supposing that no obstacle prevented him. He on the other hand (3) who has advanced so far as to apply his knowledge is in a state of full realization and knows in the strict sense of the word — for instance that this definite thing is A, As compared then with this third, both of these first mentioned possess knowledge only in potentiality: but they do so in different senses, the one because in order to become a man of knowledge he must have been transformed by learning and in many cases changed from the directly contrary state: the other because, while possessing, though not employing (say) perceptive faculties or grammatical principles, he can proceed to use them when he wishes.

Suffering or impression similarly is not used in one single sense. On the one hand, it is equivalent to some sort of destruction by the opposite; on the other hand it is rather the preservation of that which exists potentially by means of the actual and similar, much in the same way in which potential capacity' stands to actual reality. That for example which possesses knowledge rises into actual consciousness: and this is either not to be described as alteration (because its advance is towards itself and its own perfect development) or it is a different kind of alteration from that usually signified. Hence it is not correct to say that a thinking being is at the time of thinking undergoing alteration: as little as that the housebuilder is so at the time when he is building. The process therefore which transforms what is potential into what is actual in relation to a reasoning and thinking being should be called not instruction but should be known by some other name; and similarly, with reference to that which, on the basis of what is merely potential, learns and receives knowledge at the hands of that which is actual and capable of teaching, we either must not speak of it as 'suffering' an impression (as has been said) or we must recognise two different forms of alteration, the one a transition into the merely negative phase of a previous state, the other a transition into the established and natural condition.

In the sensitive subject the first form of transition is effected by the generating parent: after birth however the subject born comes to possess sensation in the further way of an intelligent experience. The actual exercise of sense comes to be used in fact as equivalent to thought, with this difference, however, that in the case of sense the objects which stimulate the faculty into action — that is the objects of sight, hearing and of the other senses, come from outside. The reason of this is that sense-perception when in active exercise deals with individual objects, whereas intelligent experience is concerned with universals: and these last are in a way contained within the mind itself. Hence it is within a man's own power to think whenever he wishes: but sense-perception is not thus in his own hands: because the object of sense must be beforehand present. The same holds good also of the sciences that deal with sensible phenomena: and this too for the same reason, because the objects of sense are individual and external.

We must however postpone the fuller discussion of this subject to another occasion. At present we may regard this much as settled — that just as what is described as potential is not used in one single sense, but on the one hand in the sense according to which we should speak of the boy as able potentially to be a general and on the other hand in that according to which we should say that the man in prime of life is potentially so able: so also is it with the power of sense-perception. Since however the distinction in question, although we have settled that the two senses are different and also how they are different, is not recognised by language, we must employ the words impression and alteration as current terms. But, as has been said, the faculty of sense -perception is potentially what the object of sense is actually. During the process of perception then the faculty of sense is not similar to its object; but after the impression, it is assimilated and becomes analogous to it.


In dealing with the senses separately we must begin by a description of their objects. The so-called object of sense-perception may mean three different things, of which two are said to be perceived directly in themselves, the third incidentally and with regard to its concomitants. Of the two firstmentioned, one is special and confined to each one of the senses separately, the other is common to them all. By the special is to be understood that which it is impossible to perceive by any other sense than that appropriated to it and with respect to which that sense cannot be deceived. So it is that colour stands to sight, sound to hearing, flavour to taste: touch, however, it must be added, deals with a number of different qualities. Each single sense in fact discerns these different qualities, and is subject to no delusion as to whether it be a colour or whether it be a sound that it perceives: its only doubt is zvhat it is that is coloured or zvhere it is, or what or where is the body that is sounding. Such are the objects of perception which are said to be peculiar to each separate sense.

The common sensibles are movement, rest, number, figure, magnitude; such properties being peculiar to no one single sense but shared in common by them all. Movement for instance is perceived at once by touch and by sight.

By the term incidental sensible I describe such a case as when a certain white object is perceived as the son of Diares: for here there is but an incidental or indirect perception of this object, in so far as the object which is perceived is an incident or property of what is white. Hence then the organ of sense is affected in no way by the object of sense so far as it is such and such a person or thing. But among those objects of sense which are perceived directly in themselves, it is those special to the separate senses that are strictly the objects of perception and those for which the essential nature of each sense is naturally adapted.


Sight then has for its object what is visible. This visible itself is colour and something which may be described, although there is no one term by which to name it — its nature will be evident as we proceed. Meanwhile, let us repeat, the visible is colour. This is that which diffuses itself over what is visible in itself, meaning by ' in itself not that it is so in its very conception, but that it contains within itself the reason of its being visible. Now every colour is disposed to set in movement that which is actually pellucid, this being in fact its nature. Hence colour is not visible without light: the colour on the contrary of every object is only visible in light. And accordingly something must be said in the first place about the character of light.

There is then, we may begin by saying, something which is pellucid. And by pellucid is meant something which is visible, not visible by itself (to speak without further qualification), but visible by reason of some foreign colour which affects its neutral pellucidity. Of this character are air and water and also many among solid bodies, water and air being pellucid not in virtue of their qualities as water or air, but because they both contain the same element as constitutes the everlasting empyrean essence. Light then is the expression of this pellucid qua pellucid: and whenever this pellucidity is present only potentially, there darkness also is present. Light is thus almost as it were the colour of the pellucid when it is realized into full pellucidity by fire or something like the upper substance of the heavens, this upper substance possessing one and the same element with fire. Thus then we have described pellucidity and light: and have shewn light to be neither fire, nor body generally, nor even the effluvium or emanation from any body (since even in this case it would be a body of a kind) but only the presence of fire or something like it in that which is pellucid: two bodies being unable to exist at one and the same time within the same space.

This explanation of light is confirmed by the ordinary view which regards light as the opposite of darkness. Darkness in fact is really the removal of such a positive quality from what is pellucid, so that light must necessarily be its presence. Empedocles therefore and any others who have followed him have not described the phenomenon correctly in speaking of the light as moving itself and as coming some time or other, without our knowing it, into existence between the earth and the surrounding air. Such a theory is contrary at once to reason and to experience. Within the limits of a narrow space, such a process might escape our observation: but to imply that it should do so from the rising to the setting sun is to make too great a postulate. It is in fact the colourless which is receptive of colour, just as it is the soundless which is receptive of sound. But such an absence of colour is characteristic of the pellucid and of the invisible or what is scarcely visible (as darkness is generally thought to be). And the pellucid itself is also similarly dark, but it is so not when it is pellucid in actuality, but only so potentially: for it is one and the same element which is at one time darkness, at another time light. It must not however be supposed that light is exclusively the condition of seeing things: it is so only for the peculiar colour of each object. There are in fact some things which are not visible in the light, but admit of being perceived in darkness, as for instance those phosphorescent objects which cannot be denoted by any one single name, but are such things as fungi, horns, fish-heads, scales and eyes — but in none of these is the colour specially belonging to them perceived in darkness. The reason of this is matter for another argument: at present this much is clear that what is perceived in light is colour.

Colour therefore is not visible without the presence of light: this indeed we saw was the essential character of colour that it is calculated to set the actually pellucid in movement: and the full play of this pellucid constitutes light. It is an obvious proof of the existence of this pellucid that if the object be placed close upon the very eye, this object will not be seen. The colour in fact moves the pellucid substance, for instance the air, and it is only through this as it extends from the object to the sense that motion can be communicated to the visual organ.

Democritus is therefore not at all correct in thinking, as he does, that if the intermediate space were empty, everything would be fully seen, even an ant should there be one in the sky. This is really an impossibility. Vision is the result of some impression made upon the faculty of sense: an impression which cannot be effected by the colour itself as perceived; and must therefore be due to the medium which inter\'enes. An intervening substance then of one kind or another there must necessarily be: and were this inter\'ening space made empty, not only will the object not be seen exactly, but it will not be perceived at all.

We have thus shewn why colour must be seen in light Fire is seen under both conditions, both in darkness and in light: and this necessarily: for it is by means of fire that the potentially pellucid becomes so actually.

This same account holds good likewise of sound and smell. Neither produces perception by actual contact with the organ: the scent and the sound move the intervening medium: and this medium moves in turn each of the two sense-organs. Thus, in this case also, if the sonorous or odorous object be placed close upon the organ itself, it will produce no perception. Nor is this true only of these senses: it is really the case with touch and taste as well, though apparently it is not so — a fact of which the reason will be afterwards evident. This intervening medium is in the case of sound air, in the case of smell it is some element found both in air and water which has no name assigned it, but which, just as the pellucid serves as medium in the case of colour, so in the case of what possesses smell is present as a common quality in both of these. And thus it is that even animals which live in water seem to possess the sense of smell: man and all other animals that breathe cannot smell unless when inhaling air. The reason of this will be stated afterwards: for the present we must first proceed to determine the nature of sound and hearing.


Sound may be regarded from two aspects, either as potential or as actual: for there are some things which we say have no sound, as for example sponge and wool, whereas we say that others have, as for example bronze and all hard and smooth substances, because they possess potentially the power of making sound: that is, they are able actually to create a sound between the thing sounding and the sense of hearing. As for actual sound, it is always of something on something and within something, for it is a stroke which produces sound. Hence also it is impossible for sound to take place with only one object; since the object striking must be different from the object struck. Thus the object sounding sounds upon something: and the stroke does not take place without some movement. It is not however, as has been already said, the striking of any object whatever that produces sound: wool, for instance, produces no sound when struck, but bronze and all objects that are smooth and hollow do so. Bronze does so because it is smooth: hollow substances produce many sounds after the first blow, from their reverberation, because the air that has been put in movement cannot find an exit. Further, sound is heard in air, and in a less degree in water. It is however neither air nor water that is the essential condition of sound: there must be a percussion of solid bodies against each other and also against the air, as happens when the air that has been struck remains and is not dissipated. Thus the air emits a sound if it be struck quickly and vehemently; that is, the movement of the person striking must precede the dispersion of the air, just in the same way as one would have to strike quickly a heap or line of sand in motion so as to anticipate its dispersion.

An echo is formed when, from air which has been compressed into one mass by some receptacle which has bounded it and prevented it from being dissipated, the air constituting sound is repelled back again, just as a ball may be made to rebound. It appears in fact that an echo is always formed, though it is not always distinct and audible: and this is because the same thing happens to sound as happens also in the case of light. For light never ceases to be reflected: otherwise there would not be everywhere light, but (with the exception of that spot on which the sun's rays directly fall) darkness: only while light is thus continually reflected, it is not reflected in the same way as it is from water or bronze or any other polished substance, so as to produce the shadow, by which light is bounded.

Vacuum or empty space is rightly said by some to be the indispensable vehicle of hearing: for the air is held to be empty, and it is this which causes hearing when it is put in movement as one continuous and connected body. At the same time, by reason of the easy dissipation of the air, no sound whatever is produced unless the object struck be smooth and polished: in which case the air is made, through the even surface, one throughout, because the surface of every smooth body is one.

Every object then so constituted as to set in movement the air extending continuously in one stream until it reach the hearing is sonorous, and hearing is itself attached by nature to the air: and because the sound is in the air, the movement of the air without sets in movement the air which is within. And hence an animal does not possess the sense of hearing in all parts of its body, nor does the air penetrate it at all places, because the organ which requires to move itself and is endowed with psychical capacity does not find everywhere that air on which its exercise depends. Thus then in itself the air is by reason of its ready dissipation soundless: but when it is prevented from dispersion, the movement of this compressed air produces sound. And the air contained within the ears is lodged deeply in them so that it may remain unmoved, and may thus perceive exactly all the different kinds of movement. Hence also the reason why we can hear in water, viz. because the water does not enter into the congenital air itself, nor even, in consequence of the convolutions, into the ear itself: indeed, when this does happen, hearing becomes impossible. Nor again is hearing possible in case the membrane of the ear becomes exhausted, just as similarly vision is destroyed when the hard covering or cornea of the pupil is impaired. (It is in fact a test as to whether we hear or not if the ear continues to sound just like a horn: for the air contained within the ears [though undisturbed as we have seen by outer things] is moved perpetually with some peculiar movement of its own: although the noise coming from outside is something external to the ear and not peculiar to it) It is then on this account that it is said we hear by means of something void and resonant, because we hear by means of that which contains the air confined within it.

Whether then, we may ask, is it the object striking or the object struck that makes the noise? May we reply that it is both, though each in a different manner? for sound is the movement of anything that can be moved in the same manner as those particles which bound off from smooth surfaces when struck. Everything however, as has been said, does not sound when striking and when struck: for example, a pin does not when struck by another pin: it is necessary that the thing struck should be smooth and even, so that the air may bound off and be agitated in a mass.

The different qualities of sonorous objects are displayed in the actual sounds which they emit. For, just as colours are not visible without light, so in like manner it is impossible to distinguish the acute note and the grave independently of sound. These terms are applied metaphorically from the analogy of objects of touch, the acute or high note moving the sense to a great degree within a short space of time, the grave or low to a small degree within a large extent of time. Thus then it is not a correct account to say that the sharp is rapid or the heavy slow: but the celerity of the action leads to a rapid movement in the one case, just as the tardiness leads to a slow movement in the other. And there does seem to be an analogy between these tsvo forms of sound and the sharp and blunt as perceived by touch: for the sharp pierces, as we may say, while the blunt, as it were, pushes, the one producing its movement in a short, the other in a large expanse of time, and thus as a result the one comes to be quick, the other to be slow. Thus much then on sound in general.

Voice is the sound produced by an animate being: no inanimate object being said to speak except in virtue of the similarity between it and the human voice, as is for instance the case with pipe and lyre and all other inanimate objects which possess those qualities of pitch and measure and articulation which seem to characterize the human voice also. Many animals however do not have a voice, as is the case with all bloodless animals, and is among sanguineous species the case with fishes — those which are said to speak, as is the case with the fishes in the Achelous, only in reality making a noise with their gills or with something of this kind. And this is only what might have been expected. Sound indeed is but a movement of the air: but voice is the sound of a living being, and this too not with any chance part of the body. But as sound is always the result of something striking something else and doing so in something, viz. air, it follows that it is only those objects which take in air that possess a voice. Now nature uses the air which has been inspired for two functions, just as it employs the tongue at once for tasting and articulation — functions of which the one, viz. taste, is necessary, and thus belongs to the majority of animals, whereas the other, i.e. intelligible speech, is for ideal ends. In this same manner, nature employs the breath at once to regulate the internal heat as something necessary (a fact of which the reason will be stated elsewhere), and also to frame speech or voice as something contributing to our nobler ends in life.

To inhale this breath the organ we employ is the throat, and this itself is subservient to another part, the lungs. It is in fact by means of this part that land animals possess more heat than others. Now the region round about the heart first stands in need of inhalation: and therefore on inspiration air necessarily presses in. And so the inhaled air when the vital principle in these parts of the organism strikes it against the so-called windpipe is what makes a vocal utterance. For, as has been said, all the sounds made by animals are not vocal: it is possible to make a noise even with the tongue or in the way that people do in coughing: for voice, on the contrary, the organ striking must be animate and must be accompanied by some mental image. Voice, in fact, is sound possessed of meaning: it is not merely a reaction against the air inhaled, as is the case with coughing: rather with this air we strike the air within the windpipe against the windpipe itself.

This explanation of the voice is confirmed by the fact that it is impossible to speak when inhaling air or respiring, but only when we hold the breath: because in checking thus the breath we move the air that has been taken in. This also explains why fishes are devoid of voice: viz. because they have no windpipe, this organ itself being absent because fishes do not inhale the air nor yet respire — a fact of which the reason must be discussed elsewhere.


Smell and its object are less easy to determine than the other senses which we have discussed: we do not see, in fact, what is the specific character of smell so clearly as we do that of sound or colour. The reason of this is that this sense is not developed in us to nearly the same degree of delicacy as it is in other animals. Man*s sense of smell is really poor: he never perceives the scent of anything odoriferous unless when it is accompanied by either pleasure or pain — a fact which seems to point to a want of delicate exactness in the organ. It is, we may suppose, with similar limitations that hard-eyed animals perceive colours: we may imagine, that is, that they become conscious of the different kinds of colours only in so far as they create fear or its opposite: and it is in a correspondingly indirect fashion that men perceive smells. And thus, while the sense of smell is analogous to the sense of taste, and the specific kinds of flavour resemble the different sorts of odour, we possess the sense of taste in a condition of greater perfection, because taste is itself a species of the sense of touch: and in man the sense of touch reaches the greatest sensibility. As regards the other senses, man falls short of many animals: in touch he far surpasses them in the delicacy of his perceptions. Hence also man is the most intelligent of animals. A proof of this is that, within the human species, men are of good or bad natural parts in virtue of this very organ of sense and of no one other sense: the hard-fleshed being dull of understanding, while the soft-fleshed are gifted with good natural ability.

Smells are like flavours, one sweet, another bitter. While however, in some bodies smell and taste correspond, both for example being sweet, in others they are opposed to one another. There are also smells which are pungent, and harsh, and sharp, and oily. But as we have said, because smells are not so clearly distinguishable as flavours, they have received their names from these latter in virtue of the similarity in the things. Thus the smell of saffron and the smell of honey are alike called sweet, that of thyme and such-like objects is called pungent, and so similarly in other cases.

[There is a further point of resemblance on the part of smell.] Just as hearing perceives at once the audible and the inaudible, vision the visible and the invisible, and so also with each one of the other senses; smell similarly perceives at once the odorous and the inodorous, whether, as is the case also with what is tasteless, the object be inodorous because it is utterly impossible that it should have a smell, or simply because it has a faint and bad smell.

Like the other senses, smell also forms its perceptions through some intervening medium, as for example, air and water: for water-animals as well as land are held to have the sense of smell. This also is the case with blood-possessing and bloodless animals, and further with those which fly in air, many of them being brought from a great distance to their food after having smelled it. And hence in fact it appears to be a disputed question whether all animals smell in the same manner. Man only perceives a smell while inhaling the breath: when not inhaling but breathing it forth or checking it, he has no sense of smell, no matter whether the object be far away or close at hand, nor even if it should be placed on the inside of the nostril. And it is indeed a fact common to all animals that an object placed actually on the organ itself is not perceived: but the inability to perceive an odour without inhaling breath is a trait peculiar to man, as will in fact be found on trial. And thus, we might conclude, bloodless animals as not inhaling breath must have some other sense beyond those we have mentioned.

This, however, is impossible, so far as they actually have a sense of smell; and their perception of what is pleasant or disagreeable is the sense of smell. And further, such animals are found to be destroyed by the same violent odours as destroy men, such as asphalt and brimstone, and the like; so that (it follows) these bloodless animals must also have the sense of smell, although it be without inhaling breath.

There seems at the same time to be a difference bet^\'een this organ as possessed by man and as possessed by other animals, similar to that between the visual organs of men and those of hard-eyed animals. The former have a protection and, as it were, an envelope in the eyelids, which must be moved and drawn apart in order to enable the animal to see, whereas hard-eyed animals have nothing of this kind but see at once what happens in the medium* of the pellucid. Similarly the organ of smell is, in the case of some animals, uncovered just as is the eye, while, in the case of those inhaling air, it has a covering which is opened out on drawing breath, by the dilatation of the veins and pores. Hence animals that inhale air cannot perceive a smell in water, because in order to smell they must inhale and this is impossible in water. Smell, it should be added, is of what is dry, just as taste is of what is liquid, and the organ of the sense of smell is potentially of such a nature.


Taste has for its object something tangible, and, for this reason, it is perceived as little as the object of touch through the medium of any foreign body. And the substance in which flavour lies — that is to say, the gustable — is contained in what is moist as its material substratum, and the moist itself is something tangible. Thus, were we in the water, and were any thing sweet cast into it, we should perceive it, the perception in this case being the result, not of the intervening medium, but simply of the mingling of the sweet thing with the water, as is the case with what we drink. Colour, however, is not perceived by a similar process of combination nor by emanation. Here then, in regard to taste, there is nothing corresponding to a mediating substance, but, on the other hand, as the object of vision is colour, so the object of taste is flavour. Now nothing produces the sense of flavour without moisture; everything that does so, possesses moisture either actually or potentially. So it is, for instance, with the saltish; for it is easily dissolved and it readily combines with the moisture of the tongue.

[In its objects, taste is as comprehensive as sight or hearing.] Sight, we saw, is concerned at once with the visible and invisible (darkness, for instance, is invisible, but is nevertheless distinguished by the eyesight), and also with the excessively bright, which is likewise invisible, though in another manner than darkness. Hearing, in like manner, perceives both sound and silence (of which the one is audible, the other inaudible), and is also directed to excessive noise, just as sight dealt with the overbrilliant, great and violent noise being inaudible much in the same way as the slight and feeble. And here further it should be noted that the name invisible is used not only to denote that which is absolutely and entirely so, in the manner in which we use the word impossible in other cases; it denotes also that which does not possess its normal qualities or possesses them only imperfectly, as we speak of something as without feet or without kernel. Taste then, has in this same way a perception at once of the sapid and the insipid, meaning by this last that which has a small and feeble flavour or a flavour which destroys taste altogether. Of this distinction the drinkable and undrinkable is thought to be the origin, for taste embraces both, although there is this difference, that the one is destructive and injurious to the taste, while the other is naturally adapted to it. And the potable or drinkable is common at once to touch and taste.

The object of taste being liquid, it follows that the organ which perceives it must be neither actually moist nor yet incapable of being rendered moist: for the taste is affected in some way by the object of taste as such. Hence it is necessary that the organ of taste which admits of being moistened should be rendered moist without losing anything of its own nature and without being moistened in itself. This is confirmed by the fact that the tongue has no sense of taste when it is either very dry or very moist: for in this latter case, it is the moisture with which the tongue has been previously imbued that is touched, rather than the flavour applied to it that is tasted. The case, in fact, is just like what happens when one, after having tasted beforehand some strong flavour, proceeds to taste some other substance, or to the way in which everything seems bitter to the sick because the tongue with which they taste is filled with flavour of this bitter character.

The specific kinds of flavours are, as in the case of colours, firstly simple opposites, viz. the sweet and bitter: secondly, the flavours allied to each of these — i.e. the oily and the saltish: thirdly, the flavours intermediate between these, viz. the pungent, the rough, the astringent and the piquant: these being in fact the different flavours which are generally recognised. Thus then the faculty of taste is that which is potentially of this character: the object of taste is that which makes it actually so.


Touch and its object may be considered in the same way. Thus if touch be not one single sense but a variety of senses, the objects of touch must be also several. And it is in fact a question whether the sense of touch includes several senses or whether it is one sense only, as also what is the organ which is adapted to perceive the tangible, whether, e.g., it is the flesh and in the case of other animals some corresponding part, or whether, on the other hand, this is merely the inter\-ening medium, the ultimate organ of sense being something else which is within. For, while all the other senses are held to be related to some pair of opposites — sight, for example being directed to the white and black, hearing to the acute and grave, taste to the bitter and the sweet — the object of touch presents us with many pairs of opposites — such as hot and cold, dr\' and moist, hard and soft, and others of like character.

A partial solution of this difficulty lies in the consideration that in the case of the other senses also there are several pairs of opposites. Thus in sound we recognise not only the high or low pitch of the notes, but also their strength and weakness, their roughness and their smoothness, and so forth. Colour similarly has a number of different aspects. Still this consideration does not let us see what is the one common object falling to the sense of touch as sound falls under hearing.

Another question which suggests itself with reference to touch is whether its organ is within, or whether it is not within, but is immediately the flesh. No conclusion can be drawn from the fact that the perception of touch takes place simultaneously with actual contact. If we were to frame a membrane-like substance and stretch it over the flesh, we should still, no less than before, perceive the object immediately after touching it. Yet it is evident the organ of sense is not contained within this: and of course if the membrane were naturally united with the flesh, the perception would pass through it still more rapidly.

This part then of the body seems to be related to us much in the same way as if air were to encircle us about: we should then be thought to perceive both sound and colour and odour by one single medium, and sight, hearing and smell would be regarded as but one single sense. Now however, as matters stand, by reason of the difference in the organs by which the movements are effected, the organs of sense which we have mentioned are clearly seen to be different from one another. W'^ith regard to touch, however, this point is obscure. For it is impossible that the animate body which feels touch should be composed of air or water, seeing that it must be something compact. It remains then that it should be compounded of earth and such like elements as the flesh and its counterpart is understood to be. The body then must be simply the natural medium for the sense of touch, as the means by which its sensations, which are several in number, are communicated. The multiplicity of these sensations is shewn by the sense of touch located in the tongue: for here at one and the same part is located the sense at once of all tangible objects and of flavour. Were then the rest of the flesh to perceive flavour also, taste and touch would appear to be one and the same: whereas, as matters stand, they are actually two, because the organs of the one sense cannot take the place of those of the other.

There is a question which might be started here. Every body, it will be granted, possesses depth, that is, is of the third dimension, and two bodies with some third body between them can never come into contact with one another. Now neither the moist nor the fluid can exist independently of water: they must either be or have water. But those objects which touch one another in water, seeing that the edges are not dry, must necessarily have between them water with which the extremities are filled. If however this be true, then it is impossible for one object really to be in contact with another in water, and the same thing holds good with objects in the air: the air standing in the same relation to the objects in it as that in which water stands to the objects in water, although we rather fail to notice, just like aquatic animals, whether the fluid touches on the fluid.

The question then naturally arises whether there is one mode of sensation for all objects equally, or whether different kinds of objects are perceived in different manners. Popular thought accepts the latter view, and holds that the perceptions of touch and taste take place through immediate contact with their object, while the other senses operate at a distance. This however is not really the case. We really perceive both the hard and soft through media, just as we also do the sonorous, the visible, and odorous: the only difference being that in the one case the objects are further off, in the other case more close at hand. And thus, by reason of the close proximity, the fact escapes our notice, the real truth being that we perceive all objects through the intervention of some medium, although we fail to observe it in the senses we have mentioned. Yet, as we said before, were we to perceive all the objects of touch through a membrane of whose intervention we were unconscious, we should be in the same condition as we are in now both in water and in air, in which we imagine ourselves to touch the very objects themselves, and think of no intervening medium.

There is, however, this difference between the object of touch and the objects of sight and sound, that, in the case of the latter, perception is the result of some action on the part of the medium towards us, whereas in regard to the objects of touch we perceive not by means of, but along with the medium; just like a man who has been struck through his shield, where it is not the shield which by being struck has hit the man, but the two which have been struck together. Altogether, in short, the flesh and tongue seem to stand in the same relation to touch as that in which air and water do to sight, hearing, and smell. In the one case too, as little as in the other, would perception ensue on direct contact with the organ of sensation, as for instance by placing a white object on the very extremity of the eye. From this it is evident that the organ of touch is internal. For the same thing must happen in regard to touch as in regard to other senses. There, when anything is placed upon the actual organ, no perception follows; it is however perceived when placed upon the flesh, and hence, we may infer, it is the flesh which serves as medium for the sense of touch.

It is then the different qualities of body qua body that are apprehended by the touch; such qualities being those which distinguish the different elements, viz. hot and cold, dry and moist, concerning which we have spoken before now in our Treatise on the Elements. And the organ fitted to perceive them by the touch and that in which what is called touch primarily inheres is a part which is in capacity what the objects of touch are in full actuality. For perception is a sort of passive impression, and thus the object which is acting makes the organ, which is potentially the same with it, to be actually so as well. Thus we do not perceive that which is hot or cold, or hard or soft to the same degree as we ourselves are, while we perceive the states that pass into extremes, sense-perception being as it were a sort of mean between the opposition in the things of sense. And hence it is that sense discriminates its objects; that which occupies the mean judging of the two extremes because it becomes for each of them its opposite. And just as that which is to perceive the white and black must be actually neither of them but potentially both, as is similarly the case with the other senses, so also, in the special case of touch, it should be neither hot nor cold.

Touch, again, is occupied at once with the tangible and the intangible, just as we saw that eye-sight was in a way perceptive both of the visible and the invisible and that the other senses equally applied themselves to opposites. By the intangible must here be understood both that which presents too slight differences to be discriminated by touch, (for instance, air,) and also those objects of touch which are in such excess as to be destructive of all sense-perception. A sketch has thus been given of the separate senses.


The general character of sense in all its forms is to be found in seeing that sense-perception is that which is receptive of the forms of things sensible without their matter, just in the same way as wax receives the impress of the seal without the iron or the gold of which it is composed and takes the figure of the gold or bronze but at the same time not as bronze or gold.

Similarly, sense receives the impress of each object that possesses colour, or flavour, or sound, not however, in so far as each of them is such and such a definite individual, but rather so far as it is of such and such a general character, and relatively to its notion. An organ of sense-perception then is reached so soon as any part displays this power of apprehending the general character of objects. And thus the organ and the faculty of sense are essentially and fundamentally the same, although they manifest themselves in different ways; otherwise in fact, the faculty perceiving would be as it were a sort of magnitude: whereas neither the essential character of perception nor the faculty of sense can be described as a magnitude — rather it is a power to read the essential notion of the object.

These considerations shew why sentient impressions in excess destroy the organ of sense. The reason is that if the movement of the organ of sense be too strong, the relation, which, as we have seen, sense involves, is broken, much in the same manner as harmony and tone become discordant when the strings are violently struck. The same fact explains also why plants possess no sense-perception although they have a psychic element and are impressed in some degree by things tangible, becoming, as they do, both hot and cold. The reason is that they do not possess that faculty (which sense implies) of acting as a mean between extremes, and have no fundamental capacity for receiving the form only of the things of sense: but that on the contrary, at the same time as they receive the form of anything, they receive the matter likewise.

The question might be further raised whether that which is without the sense of smell could be affected by odour, or that which is without the faculty of vision by colour, and so on, in like cases. In answer to this we may reply that if the object of smell be odour, it is the sense of smell (if anything) which odour calls into exercise; and therefore none of those objects that are without the faculty of smell can be affected by odour, (the same account being given also of the other senses); nor indeed can any of those objects which have the faculties of sense perceive anything except -in so far as they have some particular sensitive capacity. The matter will be clear also in the following manner. Neither light, nor darkness, nor sound, nor smell, can produce any effect on bodies, although the substance in which they are contained may do so, just as it is the air which accompanies thunder that breaks up trees. Tangible qualities, however, and flavours do themselves act on bodies; other\vise, in fact, by what would things inanimate be affected and altered? Will not then, it may be said, other sensible qualities act also in this manner? Or is the truth this — that every body cannot be affected by smell and sound; and those objects which are affected by them (as, for instance, air,) are indefinite and shifting: for the air gives out odour as if it had been subject to an impression. What then, it may be said, is smell but an impression of this same kind? And to this we must reply that smelling over and beyond this mere impression means perceiving, whereas the impression of the air only makes it quickly perceptible.



The five senses just enumerated — sight, hearing, smell, taste and touch — would seem to comprise all our perceptive faculties and to leave no further sense to be explained. The following considerations will help to make this clear. Let it be granted that we, as matters stand, perceive everything of which touch is the appropriate sense, since all the properties of the tangible as such are perceived by us through touch: and let it be allowed, further, that the absence of any faculty of sense-perception involves the absence of the corresponding organ. Now all those objects which are naturally known by actual contact are perceived through the sense of touch, and this we actually possess: those objects, on the other hand, which are known through media without contact on our part, are perceived through the elements such as air and water. (Thus if several objects of sense, different in kind from one another, are perceived through one such element, it follows of necessity that any one possessing one such organ must have the power also of perceiving both qualities: so that for instance, if the organ is composed of air, and air is the medium both of sound and colour, the one organ will perceive both qualities. If, on the other hand, there be several elements acting as media to one and the same object — for instance, both air and water, as being both pellucid, act as media for colour — the possession of one only of these media will ensure the perception of that which can be seen through one or other medium.) Now it is from these two alone among the elements — that is, air and water — that the organs of sense are constructed. (Thus the pupil of the eye consists of water: the organ of hearing is composed of air: the sense of smell depends on one or other of these two.) As for fire, on the other hand, it is either a constituent in no one of the organs of sense or it is a common element in all, as there is no faculty of sense which can act independently of heat; and as regards earth, it is either present in none, of the organs, or it is chiefly incorporated in a special manner with the touch. Hence then no element is left to act as an organ of sense-perception outside air and water. Now, as matter of fact, several animals do possess the organs so constituted. Thus, then, we may venture to conclude, all the senses are possessed by those animals which are not imperfect nor mutilated; even the mole is found to have eyes underneath its skin. And thus, unless there exist bodies differing from those we know, and unless there are properties of substances which are found in none of those around us, it would follow that no sense whatever can be wanting to us.

Nor can there, in the next place, be any one special organ for those common properties which we perceive in connection with each perception — such properties, viz., as movement, rest, figure, magnitude, number and unity. All of these are perceived as some modification or other of movement. Thus, for instance, niagnitude is perceived in connection with such movement, and this also is the case with figure (a kind of magnitude) while rest is perceived by the absence of movement. Number, on the other hand, is apprehended by the negation of continuity, as also by the individual senses, because the object of each sensation is a unit. It is, therefore, clearly impossible that there should be any one particular sense attached to any of these forms, as for instance movement. Were there in fact such a special sense appropriated to the common sensibles, we should perceive them only in the way in which we now perceive something to be sweet through seeing it — because, that is, we happen to possess from past experience a perception of two qualities united in one object, and thereby, when the two qualities coexist, we know them together. Apart, indeed, from such co-existence of the two qualities, we should have no perception of them except incidentally, just as we know the son of Cleon, not as such, but as a white object, to which it is an incidental concomitant, to be the son of Cleon. But when we reach the common sensibles we find we have a common perception of them which enters into all the senses, not a perception incidentally united with some single sense. There is, therefore, no one special sense assigned to the common properties of objects of sensation; for were there only such a special sense, we should never perceive them except in that incidental manner in which, as has been said, we see through something white the son of Cleon. At the same time, the faculties of sense do perceive the qualities that belong to adjacent senses incidentally, but they do so not as separate senses in themselves, but in so far as they meet in one, when one perception takes place simultaneously with another in regard to the same object. It is, for instance, in this manner that sense perceives gall to be both bitter and yellow: it is not the part of any separate sense to say that both qualities are in union: this, indeed, is just the reason why people are deceived, and led to suppose that if a fluid be yellow it must be gall.

The question may now be raised, why is it that we have several senses, and not one only, in order to perceive these common properties of sense } The reason may be that it is to prevent the common qualities associated with particular sensations, such as motion, magnitude, and number, escaping possibly our observation. Were sight the only sense which we possessed, restricted, say, for instance, to white colour, all other qualities would readily escape our notice, and would be' thought to be the same with the reports of particular sensations, in consequence of the manner in which such qualities as colour and magnitude accompany each other. On the other hand, with the arrangement which prevails, the presence of the common qualities in other objects of sensation makes it evident that each of them is different.


In addition to actually seeing and hearing, we perceive also that we see and that we hear. We must then perceive that we see either by means of eye-sight itself or by some other sense. In the latter case, however, there will be one and the same sense relating to the eye-sight and to the colour which is its object: and thus there must either be two senses concerned with one and the same object or the sense must itself possess the perception of itself And, further, even if the sense which thus perceives sight were different from sight itself, this would either involve another sense ad infinitum or there must at last be a sense which perceives its own action. We must, therefore, ascribe this faculty of sense-perception to the original sense itself.

Here, however, a difficulty meets us. To perceive anything by sight is, it may be said, to see: and it is colour, or what possesses colour, that is seen. Hence, it may be thought, the original sense must, in order to perceive the seeing organ, possess colour also. The difficulty so raised shews that perception by sight is not used in one single sense; even when we see nothing we are still able to distinguish by the eye-sight both darkness and light, though not, it is true, in the same manner. Further, however, there is a sense in which the organ of sight may be said to be coloured: because the perceptive organ is in each case suited to receive the object of sense without the matter of which it is composed. Hence in fact the reason why, even after the objects of sense have passed away, the perceptions and the images which represent them continue to subsist within the perceptive organs.

The object of sense is in fact, at the moment when it is perceived, identical with the actual exercise of sense-perception, although it is true the aspect which the former presents to us is different from that of the latter. Thus it is, for example, with sound as actually expressed and hearing as actually exercised: one possessed of the sense of hearing need not actually hear, and that which is capable of producing sound need not be always actually sounding: it is only when that which is capable of hearing actually realizes itself, and that which is capable of sounding actually expresses sound, that at one and the same time hearing in full activity and sound in full activity are attained, so that there would be said to be hearing on the one side, sounding on the other. Now, if it be in the object as it is being produced that both movement and productive action as well as receptivity take place, it follows that both actual sound and actual hearing must be contained in that which is potential: for it is in what is passive that the action of what is able to create and move displays itself — a fact from which it follows as a corollary that the cause of movement need not itself be moved. Thus then the actual expression of the sonorous is sound or sounding, the actualization of the capacity to hear is hearing as completed or in process: both sound and hearing being taken in a twofold sense. The same account holds good also of other senses and their objects. For just as creative action and passive receptivity are manifested in the subject which receives impressions, not in the object which produces them, so also the actualization at once of the object and of the faculty of sense lies in the faculty of sense. Sometimes both states have names assigned them, as is the case with the terms 'sounding' and 'hearing': sometimes again the one or other is without a name. Thus the actual exercise of sight is known as seeing, but the actual existence of colour when perceived has no distinctive name; and so similarly the actual operation of the gustatory faculty is known as tasting, while flavour, when actually felt, is without any characteristic name. Thus then, since the object and the faculty of sense-perception are as actually operative fundamentally one, though differing in the aspect which they respectively present, it follows that hearing and sound when used in this sense must be destroyed and preserved together, and so also must it be with flavour and taste and with the object and the organ of the other senses; while, on the other hand, if object and organ be understood as in potentiality, there is no necessity that this should happen.

This relation of the object to the subject of sensation was not rightly comprehended by the early natural philosophers. They thought that there was nothing white or black apart from vision, and no flavour independently of taste. And in so thinking they were partly right, but they were also partly wrong. For perception and its object are words employed in two senses, on the one hand as potential, on the other hand as actual: and although in the latter of these senses their assertion was correct, in the former it does not hold good. They, however, maintained their doctrines without any qualification whatever, when they were really dealing with terms which are not employed in so unambiguous a manner. [Perception does, however, always involve a close relation between the subject and the object, as may be seen by reference to sound and hearing.] Harmony, it will be granted, is a species of vocal sound; and sound and hearing are in one sense identical (though it is true there is another sense in which they are not the same). Now, since harmony is a ratio, hearing, it follows, must be also a sort of ratio. This is in fact the reason why every excess, whether it be high or low, destroys hearing; just as similarly every excess in flavours destroys taste, every excess among colours, whether over-brilliant or overdark, destroys vision, or just again as all violent odours, whether sweet or bitter, destroy the sense of smell. Perception, in fact, always involves a sort of ratio between the object and the faculty of sense. Hence also it is that flavours are pleasant, when, being pure and unblended, they are combined in definite proportions, as is the case with what is piquant, or sweet, or, saltish — flavours which are pleasant when combined in due proportions, and that in general the mixed and blended is attended with the greater pleasure. Harmony, for example, brings us more pleasure than the single bass or treble, and to the sense of touch a moderate temperature is pleasanter than what is simply either hot or cold. Sense-perception thus involves this relative proportion: while those objects which exceed this ratio either produce pain or destroy the action of sense.

Each single sense, we have before remarked, apprehends the object appropriated to it: and existing in its organ of sense as such it judges of the distinctions in the object which is subject to it eye-sight, for instance, judges of the white and black, taste of what is sweet and bitter, and so on. But furthermore, we discriminate between what is white and what is sweet and between each of the objects of sense in comparison with every other: and thus the question rises, what is it which enables us to apprehend this difference? It must be sense: because the qualities to be compared are objects of sense. But if sense be the power which thus distinguishes the different qualities of objects. It is evident that the mere fleshly organism is not the ultimate organ of sense-perception: because in that case the discriminating faculty would have to distinguish on merely coming into contact with the sensible object Thus then it is impossible for the senses taken apart from one another, to decide that what is (say) sweet is different from what is white: on the contrary, both the qualities must be exhibited to some one faculty. It is just in fact as if I were to perceive the one and you the other; it would then be evident that our two perceptions are different from one another: but still it would be necessary to have some one referee to assert the difference: and just in the same way as such an assertion is made, do thought and perception also operate.

It is clear then that the separate senses cannot apart pass judgment on separate perceptions. Nor, further, can such a judgment be passed at different times. Just as it is one and the same principle which asserts that the good and bad are different, so further when it maintains the one to be different it also at the same time maintains the other to be so also. Nor is this identity of time simply incidental: it is not, that is, as if its assertion were merely like saying " I at present assert the difference," without adding also that "the difference holds good at present" — rather the one principle, which thus distinguishes both, maintains at present the difference, and maintains it to hold good at present: that is to say, it makes the two statements simultaneously; so that its judgment is inseparable, and made in a single inseparable moment of time.

But, it may be said, the same thing, cannot as undivided and within an undivided point of time be at one and the same time moved with contrary movements. Yet if a quality be sweet it moves sense or thought in such and such a manner, while what is bitter does so in a contrary manner, and what is white must do so in a manner different from both. Must not then the discriminating faculty be simultaneously on the one hand numerically one and undivided, but on the other hand separated in the mode of its existence } The truth is, there is a sense in which this distinguishing principle perceives what is divided as divided, while in another sense it does so as one undivided faculty; because while it is divided in its application or its mode of being, it is in regard of its seat of action and as viewed numerically one single undivided principle. Or is this really impossible? Potentially, it may be said, the same subject, and that one undivided, may present opposite qualities: but this cannot be the case with its definite existence; in its operation and working these characteristics are divided. The same thing, in fact, cannot be at once black and white: and so, (/"perception and thought be nothing but a passive reception of such qualities, they cannot be impressed at one and the same time with the forms which represent these contraries.

To this objection it may be replied that the matter stands just as with the point (as some describe it), which, so far as it is one, may be regarded as undivided, while so far as it is two, it is divided. So far then as the principle of judgment is undivided, so far it is one single faculty acting in one moment: so far as it shows itself divided, it uses the same point twice at two simultaneous times. So far then as our faculty of discrimination makes use of the termination of this point as two, it distinguishes two qualities, and the objects are separated as the faculty is separated; while so far as it is one single faculty, it judges by one single act and within a single point of time.

Thus much on the principle through which, according to our view, the living being is endowed with powers of sense perception.


Two differentiae are chiefly used to characterize the soul — local movement on the one hand, thought discrimination and perception on the other. The popular mind thus comes to look at thought and understanding as a kind of sense-perception, on the ground that at once in thought and in sense the soul distinguishes and cognizes things. And in fact the older thinkers actually identify thought with sense-perception. Thus, for example, Empedocles maintains:

"Wisdom increases to men according to what they experience.”

And in another passage he observes:

"Hence variation of thought presents itself ever before them To similar effect also are the words of Homer: Of such kind is the reason."

All these writers, in fact, understand thought to be something bodily, just like sense-perception: and they suppose perception and thought lie in the apprehension of the like by the like, as was laid down at the beginning of this treatise. They should, however, before thus identifying sense and thought, have discussed the nature of error and misconception, a state which is somewhat distinctively [in opposition to inanimate things which cannot err] the condition of living beings, and in which the soul continues for a considerable length of time. Thinkers, then, who thus identify sense and thought must either, as some do, maintain all presentations of the senses to be true, or they must explain misconception through contact on the part of the dissimilar, this being the opposite of knowing like by like. But this latter explanation is entirely at variance with the ordinary view, that in reference to contraries the knowledge and the misapprehension of them are one and the same.

Manifestly, then, thought is not the same as sense-perception. The latter is possessed by ail animals without exception: the former is the property of but a few. But neither again is thought as a process leading to results now correct, now incorrect — correct thought being understanding, scientific knowledge, and true opinion, incorrect thought their opposites — neither is this process of thought identical with sense-perception. The perception of the qualities peculiar to each sense is always true, and is an attribute of every animal: thought, on the contrary, may be false as well as true, and is possessed by no animals that do not have as well intelligible language.

[Imagination, indeed, the animal does have,] but this is different at once from sense-perception and from understanding: and while imagination does not come into existence independently of sense-perception, conception is not found without the aid of imagination. But that imagination is a different kind of thought from conception or reflection is quite evident Imagination is a condition subject to our own control whenever we desire — we can represent an object before our eyes just in the way those do who, in the exercise of memory, depict something with which the fact to be recalled has been associated — but conception or the forming an opinion does not in this way depend on us because it must needs be either true or false. And, further, when we form the opinion that something is terrible or fearful, we at the same time experience a feeling of fear along with it; and the result is similar when we think anything fitted to excite our confidence: whereas, with respect to merely forming an image of anything, our condition is simply like that of those who see scenes of terror and of courage portrayed in pictures. And, again, conception includes a number of specific forms — scientific knowledge, opinion, understanding, and their opposites, the difference between which will be dealt with elsewhere. Thought, on the other hand, is regarded as different from sense-perception, and is considered to embrace under itself two main forms — viz., imagination and conception. We will therefore, first of all, settle the nature of imagination, and then proceed to the consideration of the other faculty.

Imagination, then, as that faculty in respect of which we say an image or mental picture presents itself before us, and not as it may be understood in any metaphorical or wider sense, might be supposed to be some one of those faculties or states through which we judge and conclude towards that which is true or false. Such faculties are sense-perception, opinion, scientific knowledge, reason.

The following facts, however, shew that imagination is not identical with sense-perception, (i) Sense-perception may be taken either as potential or as actual, as we see, for instance, in the eyesight on the one hand, actual seeing on the other: but a picture of imagination presents itself without the presence of sense-perception in either of these forms, as for instance is the case with our visions in sleep. (2) Again, sense-perception is always ready to hand, imagination is not so. But (3) were they as actually realized identical, imagination might be possessed by every animal. This, however, is not generally thought to be the case: the bee and ant would seem to have imagination, the worm would seem to be without it (4) Further, the perceptions of the senses are as such always true, our pictures formed by imagination are to a great extent false. And, lastly, we do not, when our senses are vigorously and carefully directed towards their object, say that such and such a thing "appears" the image of a man: it is only when we do not perceive the object clearly that the question of its truth or falsity arises. And, as we said before, pictures of imagination present themselves even to those whose eyes are closed.

Neither, again, is imagination any of those faculties which invariably reveal us truth: as, for example, scientific knowledge or thought: because imagination may be false as well as true.

It remains for us, then, to see whether opinion, which is both true and false, can be identified with imagination. But opinion is followed by belief: it is impossible, when holding an opinion, not to believe the views we have. Belief, however, is an attribute of no brute beast, whereas imagination is possessed by many. Besides, every opinion is accompanied by belief, belief by conviction, and conviction by reason; and while imagination is a property of some animals, reason is of none. It is clear, then, that imagination is neither opinion attended by sense-perception, nor acquired through sense-perception, nor again is it the combination of opinion and sense-perception. And from the facts already stated it is further evident that this opinion does not refer to something other than the object of sensation, but is restricted to that of which we have perception. Thus, for instance, it must be the combination of the opinion of white and of the sensation of white which constitutes imagination: it cannot be the result of the opinion of good and the sensation of white.

The result of such a theory would be that imagining is the direct thinking or conceiving of the object of perception. Such a result, however, is directly at variance with facts. Objects in regard to which a man's opinion or conception is quite correct, assume an image which is altogether false: the sun, for example, bears the image of being but a foot in its diameter, while at the same time the observer is convinced that it is larger than the earth* Here, then, [imagination and opinion are at variance, and if imagination be opinion] one of two things must result. Either, we must say, the man, in having this imagination, must have thrown off the true opinion which he had in presence of the fact while it remained unaltered, unless we are to suppose that he has forgotten or been led to change his views, or if he still preserves his opinion, then it follows necessarily that the same opinion is true and false. (Of course, it might be said that an opinion previously true would become false, in case the object were to alter in its character without our cognizance.)

Imagination, then, is not to be identified with any of these faculties, nor is it the result of their combination. It is, however, a law of nature that whenever one object is moved, another is moved by it. Now imagination is thought to be a form of movement, and is believed to be dependent on the senses so far as to arise only in those who perceive, and relatively to the objects of perception. And while such movement must result from sense as actually realized, and must itself be like the senseperception, this movement, it follows, can neither exist without sense-perception nor can it be the property of any that do not have perceptive powers. It follows, further, that the possessor of this faculty may be both active and receptive in many ways regarding it, and the imagination itself may be both true and false. This results from the following considerations. The perception of the particular qualities of sense is true or marked by falsity only to the smallest possible degree. But, secondly, there is the perception of the concomitance of these qualities. And here error is possible: for while sense is never mistaken in that the object is for instance white, it may be mistaken as to whether it is this thing or some other object that is white. Thirdly, we must note the perception of the common sensibles — that is, of those properties which are associated with the objects to which the particular qualities belong — such objects, namely, of perception as movement and magnitude, which are concomitants of sensible phenomena, and with respect to which it is particularly possible to be deceived in our perception. Such, then, being the varying degrees of truth in sense-perception, there will be a difference in the movement which results from the exercise of each of these three perceptive faculties. Thus the movement in the first instance is true while the perception itself is present: the movements in the other two cases might be both in the presence and in the absence of the sensation possibly false: and this especially in any case in which the object of sensation is far distant from its organ.

Thus, then, if there be nothing but imagination which possesses the attributes that have been mentioned, and this be the faculty we have described, imagination will be a movement resulting from the actual operation of the faculty of sense. And, further, since it is the eye-sight that is the most important sense, imagination has received its name from ' light/ because without light it is impossible to see. And because the pictures of imagination continue to subsist in a way resembling the perceptions of the senses, animals act frequently in accordance with the pictures which imagination offers, some (as is the case with brute beasts) because they have no faculty of reason, others because their reason is at times obscured by passion, or disease, or sleep, as is the case with man. And here we conclude our account of the nature and conditions of imagination.


We must next discuss the cognitive and thinking part of soul, whether it be separated from our other mental faculties or whether it is not separated physically, but be so only by thought and abstraction, and inquire what is the specific character of thought, and how it is that at some stage or another thought begins to operate.

Thinking, we may assume, is like perception, and, if so, consists in being affected by the object of thought or in something else of this nature. Like sense then, thought or reason must be not entirely passive, but receptive of the form — that is, it must be potentially like this form, but not actually identical with it: it will stand, in fact, towards its objects in the same relation as that in which the faculty of sense stands towards the objects of perception. Reason therefore, since it thinks everything must be free from all admixture, in order that, to use the phrase of Anaxagoras, it may rule the world — that is, acquire knowledge: for the adjacent light of any foreign body obstructs it and eclipses it Its very nature, then, is nothing but just this comprehensive potentiality: and the reason — that is, that function through which the soul is ratiocinative and frames notions — is therefore, previously to the exercise of thought, actually identical with nothing which exists.

This consideration shews how improbable it is that reason should be incorporated with the bodily organism: for if so, it would be of some definite character, either hot or cold, or it would have some organ for its operation, just as is the case with sense. But, as matter of fact, reason has nothing of this character. There is truth, too, in the view of those who say the soul is the source of general ideas: only it is soul not as a whole but in its faculty of reason: and the forms or ideas in question exist within the mind, not as endowments which we already possess, but only as capacities to be developed.

The difference, however, between the impassivity of the faculty of reason and of the faculty of sense is clear from a consideration of the organs and the processes of sense-perception. Sense, for example, is unable to acquire perception from an object which is in too great excess — cannot, to take an instance, perceive sound from extremely loud noises, nor see nor smell anything from too violent colours and odours. Reason, on the contrary, when it applies itself to something extremely intellectual, does not lessen but rather increases its power of thinking inferior objects, the explanation being that the faculty of sense is not independent of the body, whereas reason is separated from it. And since reason becomes each of its objects in the sense in which he who is in actual possession of knowledge is described as knowing — this resulting when he can apply his knowledge by himself — the reason as a developed capacity is similar to what it was previously as a mere unformed faculty though not the same as what it was before it learned or discovered: and it may in this final stage be said to think itself.

[The difference between sense and reason may be exhibited also in this manner.] There is a difference between magnitude as a simple fact and magnitude as a real notion, just as there is between water and its essential being: as indeed a similar difference holds good in most things, though not in all, there being some abstract objects in which matter and form combine together into one. It is then either by a different faculty, or by a faculty differently applied, that the mind judges of the essential nature of flesh and simple flesh itself, because flesh does not exist independently of matter, but is, like snubnosedness, a definite fact in concrete expression. With the faculty of sense it discriminates the hot and cold and those qualities of which flesh presents us with a certain aspect, whereas with another faculty, either separated from the former or standing to it in the same relation as the bent line to the same line when straightened, it judges of the essential notion of flesh.

And this distinction holds good also of abstract conceptions. The actual straight line, as occupying continuous space, resembles the concrete materially expressed snubnose; whereas the essential idea, if we allow a difference between the notion of straightness and the simple straight line, must be recognised by some other faculty. And now suppose that we define the idea of straightness as duality. It must be with a different or differently applied faculty that mind judges of this real idea: and generally just as the forms of sense can be separated from the matter in which they are embodied, so also can we draw a distinction between the different applications of thought.

The question might, however, here be raised — How, if reason is uncompounded and unaffected by impressions, and has, as Anaxagoras maintains, no community with other objects — how is it to think objects, if thinking be a sort of receptivity; for it is only in so far as there is something common to two objects that the one is thought to produce, the other to receive an impression. And the further question might be raised whether reason itself can be an object of thought For either reason must be an attribute of other things as well, in case it be held to be an object of thought not through anything outside itself, but simply in and by itself, and supposing that the object of thought is always something homogeneous: or it must have some element compounded with it which makes it capable of being thought like other real things. Or may we not rather hold that the receptivity of reason is possible only in virtue of some common element? And hence it has been already said that reason is in a way potentially one with the ideas of reason, though it is actually nothing but a mere capacity before the exercise of thought. We must suppose, in short, that the process of thought is like that of writing on a writing-tablet on which nothing is yet actually written.

Thus the reason can be thought just in the same way as can objects of thought generally. [For such objects of thought are either immaterial or material.] Now in the case of immaterial objects, the subject thinking and the object thought are one and the same: just as speculative science is equivalent to the objects and ideas of speculative knowledge (a fact, it is true, which leaves the question — why we do not always think, to be investigated). In the case, on the contrary, of those objects which are imbedded in matter, each of the ideas of reason is present, if only potentially and implicitly. And thus reason is not to be regarded as belonging to and governed by the things of sense (reason being a faculty independent of the matter of such objects), but the world of thought must be regarded as belonging to and regulated by reason.


The same differences, however, as are found in nature as a whole must be characteristic also of the soul. Now in nature there is on the one hand that which acts as material substratum to each class of objects, this being that which is potentially all of them: on the other hand, there is the element which is causal and creative in virtue of its producing all things, and which stands towards the other in the same relation as that in which art stands towards the materials on which it operates. Thus reason is, on the one hand, of such a character as to become all things, on the other hand of such a nature as to create all things, acting then much in the same way as some positive quality, such as for instance light: for light also in a way creates actual out of potential colour.

This phase of reason is separate from and uncompounded with material conditions, and, being in its essential character fully and actually realized, it is not subject to impressions from without: for the creative is in every case more honourable than the passive, just as the originating principle is superior to the matter which it forms. And thus, though knowledge as an actually realized condition is identical with its object, this knowledge as a potential capacity is in time prior in the individual, though in universal existence it is not even in time thus prior to actual thought Further, this creative reason does not at one time think, at another time not think: [it thinks eternally:] and when separated from the body it remains nothing but what it essentially is: and thus it is alone immortal and eternal. Of this unceasing work of thought, however, we retain no memory', because this reason is unaffected by its objects; whereas the receptive passive intellect (which is affected) is perishable, and can really think nothing without the support of the creative intellect.


With regard then to the exercise of reason, the thinking of isolated single terms falls within a sphere in which there is no falsity: when, on the other hand, we find both falsity and truth, there we reach a certain combination of ideas as constituting one conception: much in the same way as Empedocles said: " Thereupon many there were whose heads grew up neckless entirely:" but were afterwards brought together by friendship. In a corresponding fashion is it that those notions which are originally separate are afterwards connected, as is, for instance, the case with the two notions incommensurate and diagonal. Should the notions in question be, however, related to the past or to the future, thought then adds on the idea of time to that of mere connection. Falsehood, in fact, always involves combination and connection: even in asserting the white to be not white we bring not-white into a combination. It should be added, at the same time, that all this process might be described, not as combination, but rather as disjunction or division. Anyhow it follows that truth or falsehood is not limited to saying that "Cleon is white," but includes the judgment that he was or will be: and the process of thus reducing our ideas into the unity of a single judgment is in each case the work of reason.

Further light is thrown upon this unity of thought by considering that the indivisible and continuous presents itself before us in two forms, either as potential or as actual. There is therefore nothing to prevent us conceiving extended and thus divisible space, at the time when we think it, as indivisible (because as it actually exists it is thus indivisible): and also doing so within an indivisible moment of time, because time, just as extended length, may be conceived of either as divided or as undivided. And therefore it is impossible to state what was thought in each of the two halves of time: because, unless it be divided, there is no such half existing actually, but only potentially: although, in so far as the reason thinks of the two halves separately, it divides the time likewise, and thinks it just as two lengths. If, on the other hand, the reason think its object as consisting of two halves, then it thinks them also in a time which is spread over two halves.

With respect to what is indivisible, not quantitatively but specifically, this the reason thinks within an undivided space of time and with the undivided action of the soul [and this not as an essential property of the object which is indivisible], but as an incidental concomitant of the mental process, and thus not in so far as the mental action and the time are divisible, but rather in so far as they are indivisible. For in such objects also there is something which is indivisible, though perhaps it cannot be separated from its setting — something which makes the time and the length into one; and this also is the case with everything continuous, whether it be so in time or space. But as for the point and everything which is thus arrived at by division, and yet is in this sense indivisible, its character comes to be elucidated in the same way as negation.

A similar account holds good of other cases. How, for instance, do we come to know evil or black? We may say it is through their opposites. And thus the cognitive faculty must be in such cases potentially both qualities, while at the same time it remains at unity within itself. If, however, there be a causal mental force, which has no contrary opposed to it, such a faculty knows itself by its own agency, and is realized in full activity and independently of all bodily conditions. And thus while every statement, as for instance an affirmation, asserts something of something else, and is in every case either true or false, reason is not in every case placed between the alternatives of truth and falsehood: the conception of the notion in its real nature is intrinsically true, and is not merely an assertion that something belongs to something else. Just in fact as the seeing of the particular quality of sense is always true, while the judgment, whether the white colour is or is not a man is not always true: so similarly the conceptions which are entirely independent of material surroundings are as such always true.


Actual knowledge has thus been shewn to be identical with the object of knowledge. Potential knowledge is, it is true, in point of time earlier in the individual, although absolutely it is not even so in time, because it is from something actually existing that everything which comes into being is derived. It appears, however, that in sense-perception it is a potential faculty of sense which the sensible object transforms into actuality: in fact, the faculty is not affected or altered by the object of sense [ — rather it is realized by its object]. Hence, then, the movement implied in sense-perception is different from ordinary movement: for while movement is, as we have seen before, only the realization of something while incomplete, realization taken absolutely is something different, as relating to that which has been completed.

Sense-perception, then, in itself is like mere simple assertion and conception: when, however, the sense perceives something as pleasant or painful, it, so to speak, affirms or denies it — that is, pursues or avoids it. Pleasure and pain, then, are due to the operation of the medium state involved in sense-perception upon that which is good or bad, as such: and pursuit and aversion are equivalent to this state as actual and realized. And thus the faculty of desire and of aversion are not different either from one another or from the faculty of sense: although, indeed, the mode in which they manifest themselves is different. So similarly to the understanding the images of sense-impressions are related just as the impressions themselves are to sense: it is only when the mind proceeds to assert something to be good or bad that it either pursues or avoids its object

The soul, then, never thinks of anything as good or bad without the help of images of sense. [But this sensuous image is only a condition of its exercise]: it is simply like the air which makes the pupil of such and such a character, while the pupil itself remains different from it, in the same manner as it is also with the hearing: and all the while the ultimate faculty and equalizing medium remain one, although their modes of manifestation may be several.

This ultimate unity is, further, that by which the mind comes to distinguish between separate sensations, such as sweet and hot This has been already explained, but we may state the matter also in the following manner. There is a unity which stands towards the different sensations much in the same manner as anything which serves as limit to a series: while, further, the ideas themselves are one by the proportion and the numerical relation which makes each stand towards the other in the same relation as that in which the outward qualities are associated with one another. And here, let it be granted, it makes no difference whether we ask how this unity judges of objects that do not fall within one and the same genus, or, on the other hand, contraries, such as black and white [which do thus belong to one and the same conception]. [Consider, then the question, first of all, relatively to homogeneous objects and conceptions.] Whatever be the relation in which A (the objective quality white) stands to B (objective black); C and D [the idea of white and the idea of black] will stand to one another in the same relation as the former pair. (Hence, of course, also alternando: A will stand to C as B to D.) If, then, C and D attach themselves to some one act of mind, they will hold themselves just as A and B — that is, they will be one and the same, though their aspect or mode of existence differs; and the sameness and unity which thus attaches to them will be simply like that of the actual concrete qualities. And the same proportion would result were we to make A represent the sweet and B the white.

Thus then the reason, while employing as its materials the images of sense, grasps from among them general ideas; and in the same manner as it determines for itself within these images what is to be pursued and what avoided, so also outside the actual perception of these objects it is, when engaged merely with the images of sense, stirred up to action. [Thus then the practical reason, in dealing with the perceptions and the images of sense, translates them into ideas of what is good and evil] much in the same way as a man on perceiving a torch-light, which sense presents to himself simply as a fire, comes, by the action of the central sense, when he sees it moved, to know that It signifies the approach of an enemy. Similarly also, when dealing with mere images or notions in the mind, we calculate as if we had the facts before our eyes, and deliberate upon the future in relation to the present And, further, when the reason in the speculative sphere asserts something to be pleasant or painful, within the practical sphere it pursues it or avoids it, and, in a word, steps forth into action. Independently, however, of action, truth and falsehood are of the same character as good and evil: but they differ in so far as the two former are absolute, the two latter relative to some person or object.

As for so-called abstractions, the mind thinks them just as it might snubnosedness: for just as qua snubnosed the mind cannot conceive this abstractedly and by itself, but qua hollow can by an effort of thought conceive it without the flesh in which the hollowness inheres; so in like manner the mind, in thinking of mathematical forms, conceives them, though not really separated from objects, as if they were so separated. And in general, in fact, reason is the faculty which thinks things in their reality and truth. But as to whether the reason can think anything that is abstract unless it be itself abstract and independent of magnitude — that is a question which must be discussed at a later stage.


We will now sum up the conclusions we have made about the soul. The soul, we have seen, is in a way all existing things. For the objects of existence are either objects of sense or objects of thought: and while science is in a way identical with the objects of thought, sense again is one with the objects of sense. How this comes about is a point we must investigate.

Scientific thought and sense-perception thus spread themselves over objects, potential sense and science relating to things potential, actual to things actual. Now the sensitive and the scientific faculty in the soul are potentially these objects — that is to say, the objects of scientific thought on the one hand, the objects of sense on the other. It must be then either the things themselves or their forms with which they are identical. The things themselves, however, they are not: it is not the stone, but simply the form of the stone, that is in the soul. The soul, therefore, is like the hand: for just as the hand is the instrument through which we grasp other instruments, so also reason is the form through which we apprehend other forms, while sense-perception is the form of the objects of sense.

[The forms of reason are not however something different from the things of sense.] As there is, according to the common opinion, no object outside the magnitudes of sense, it follows that the ideas of reason are contained in the forms of sense, both the so-called abstract conceptions and the various qualities and attributes that determine sensible phenomena. And further, without the aid of sense-perception we never come to learn or understand anything: and whenever we consider something in the mind, we must at the same time contemplate some picture of the imagination: for the pictures of the imagination correspond to the impressions of the senses, except that the former are without material embodiment.

At the same time imagination is something different from affirmation and negation, for it is only by a combination of ideas that we attain to truth and falsehood. But, it may be asked, in what respect will our primary ideas differ from mere images of sense? And to this, perhaps, we may reply that they are, as little as other ideas which we frame, mere images of sense, although never framed without the help of such representative images.


The soul of animals is, as we have seen before, characterized by two capacities — on the one hand, the cognitive discriminative faculty as shared by understanding and by sense, on the other hand, the faculty of local movement. The nature of sense and intellect has been so far settled: we must now investigate the motive faculty of the soul, and ask whether it is some distinct part of it, separable either actually or by abstraction, or whether, on the contrary, it be the soul taken as a whole: and further, if it be some one part of the soul, whether it be some special part different from these usually recognised and enumerated, or whether, on the contrary, it is some one of these which have been stated.

An immediate question which arises is — in what sense are we to speak of parts of the soul, and how many are there of them. From one point of view such parts appear innumerable, and not confined merely to the "rational," "spirited," and "appetitive" parts which some distinguish, or the rational and irrational which others enumerate. The characteristics, on the ground of which they distinguish these, shew also other parts further distant from each other than these are — the parts in question being just those which we have before described — the vegetative, which is an attribute at once of plants and every animal — the sentient, which cannot be easily classed either as rational or irrational — and, further, the imaginative faculty, which is different in its action and aspect from all, while with which of them is it either the same or different is a question full of perplexities, if we assume so many distinct parts of soul. Besides these, there is the conative or desiring faculty, which would seem to be different from all, both in its conception and in its capacity for action. Now, it is absurd to parcel this out in the manner indicated. The settled wish [which is one of its aspects] constitutes itself within the rational part of soul, while the appetite and passion, which are its other factors, lie within the sphere of the irrational. And thus, if there be three parts of the soul, desire will have to be present in each of them.

To return, then, to our original question — What is the part that communicates local movement to the animal. As for the movements of growth and decay, they would seem, as they are the attributes of all animals, to be caused by those powers of production and nutrition which characterize all animal life: and with regard to respiration and expiration, as also sleep and waking, we must investigate their nature on another occasion, as they are marked by many difficulties. Our present task is to investigate the nature of local movement, and see what it is that moves the animal in the way of progressive movement Evidently It is not the mere vegetative capacity which does so. Local movement is always directed to some end, and is accompanied either by a representative image or by a desire, since nothing — unless indeed its movement be the result of force — moves without seeking either to gain or to escape something. And further, plants would be capable of local movement and would possess some part instrumental for this movement.

As little is it the faculty of sense which causes local movement. There are many animals which possess sense powers and yet continue throughout fixed and unmoved. But nature makes nothing without a purpose, nor leaves anything, mutilated and imperfect forms excepted, without that which it requires. Now the animals in question are perfect, and not mutilated^ they possess generative powers, and exhibit both development and decay. And therefore [ — if sense alone were a sufficient reason for the exercise of local movement — ] such animals would possess all the parts instrumental for movement.

Neither, further, is the ratiocinative part, nor the so-called reason, that which produces movement The speculative reason thinks nothing which relates to action, nor does it assert anything with regard to the object of pursuit and aversion: whereas movement is invariably connected with one either pursuing or avoiding something. Nor indeed, even when the reason reflects on something of this character, does it even then advise the individual either to pursuit or to aversion. Frequently, for example, the reason thinks of something terrible or pleasant, but it does not thereby produce fear: the only result is that the heart, in case the object be terrible, or some other part, in case it be pleasant, is excited. Furthermore, even when reason gives a command, and understanding bids us either avoid or pursue something, the individual is not moved accordingly, but follows the direction of appetite, as may be seen in the incontinent So also, in general, we see that the man who understands the art of healing does not on that account therefore heal, a fact which shews that it requires something besides knowledge to produce the results of knowledge: and that scientific knowledge IS itself unable to effect this end.

Lastly, desire is not fitted to produce this movement: the continent, though subject to desire and appetite, do not do these things for which they possess a desire, but follow, on the contrary, the lead of reason.


There are, however, at least two faculties which are manifestly motive — viz., desire or reason, if we regard imagination as a form of reason. Frequently, in fact, it is the pictures of imagination as against knowledge that people follow, and among animals other than man it is not thought nor ratiocination, but simply this power of representing images of sense, which guides them. Both then reason and desire are fitted to produce and lead to local movement The reason which is here intended is that which calculates for some purpose — that is, it is the practical reason, distinguished from the speculative by its end. As for desire, // is always directed to some object: in fact. It is the object at which desire aims that forms the starting point of the practical reason, although it is some particular detail which forms the beginning of the action.

It is then on good grounds that people have viewed as springs of action these two faculties of desire and practical intellect: for the faculty of desire has itself a motive force, and the intellect excites to action just in so far as the object of desire supplies it with a starting-point: just as, similarly, imagination when it moves to action does not do so independently of desire.

The spring of action thus resolves itself into one single thing, viz. the object of desire. For if there were two faculties acting as springs to action — reason on the one hand, desire on the other — they would have to move in virtue of some common character they shared. Now reason, it is found, does not act as a spring of action independently of desire: for settled wish is a form of desire, and when a man is led to act according to his reasonable conviction he is moved also in a manner corresponding to his wish. Desire, however, excites to action contrarily to reason, appetite, which so acts, being one of the forms of desire. And thus, then, it would seem, reason is always true and right, whereas desire and imagination may be both right and not right.

It is then always the object of desire that moves to action: and this is either the good or the apparent good — not good, however, as a whole, but simply that form of it which relates to action — that is, which is contingent and admits of being other than it is.

Evidently, therefore, it is such a faculty of the soul, the so-called principle of desire, which moves to action. Those, then, that divide the soul into different parts must, if a difference of powers be the basis of their separation, recognise a great variety of such parts — the nutrient, sentient, rational, deliberative, and, further, the conative or desiring — all these being separated by wider differences from one another than are the principle of appetite and that of spirited indignation.

The very opposition of desires itself attests the oneness of the motive faculty. Such opposition happens when the reason and the appetite come together into conflict and displays itself in beings with a sense of time. With such beings, reason, from its perception of the future, enjoins resistance on the mind, while appetite is influenced by a present which is vanishing: for that which is momentarily pleasant appears both absolutely pleasant and absolutely good, because the future is unseen. Now, such a conflict of desires requires that the motive agent, the principle of desire, as such, should be specifically but one: and the most primary of all is the object of desire, for this, without being itself moved, creates movement by being made an object of thought or presented before us by imagination. Numerically, however, the motive agents may be several. Now, there are three elements in motion, one being the object which produces movement, the second that by which it moves, and the third the object which is moved. Now, of these three, the object which produces movement is two-fold, being on the one hand itself unmoved, and on the other hand not only moving but also moved. That then which while it produces movement remains itself unmoved is the good as applied to action: the element which at once sets and is set in movement is the faculty of desire (for the subject desiring is moved, in so far as it desires, and desire itself is a form of movement so far as it manifests itself in action): the object which is moved is the living being.

As for the organ through which desire produces movement, that is necessarily of corporeal nature: and must therefore be investigated among the functions common to the body and the soul. If we may, however, speak for the present summarily on the subject, that which moves instrumentally must be such that in it beginning and end coincide, as is the case, for instance, with the pivot of a joint: for there both convex and concave meet together, the one acting as end, the other as beginning. Hence, while the one part is at rest, the other is in movement —that is, the two, while different in their purpose or idea, are in real magnitude inseparable: for all movement is the result of impulse or attraction, and there must be therefore always something which remains fixed, like the centre of a circle, as the source from which movement may begin.

Generally then it is, as has been said, in so far as the animal is endowed with the faculty of desire that it is capable of moving itself. But no animal can be provided with the faculty of desire unless it have imaginative power. Now, all such power is connected either with the reason or the senses: and in it other animals besides men participate.


[Desire then, thus depending on the power of representing images of sense], it falls to us to ask, besides, what is the motive Dree in those imperfect animals which possess no sense but hat of touch, and see whether it is or is not possible for imagination and appetite to belong to them. Pleasure and pain they o indeed evidently feel: and if these belong to them, then appetite, it follows, must be there as well. But it is difficult see how they can have imagination. Perhaps, however, we may say that just as their movements are vague and indeterminate, so also they possess the powers in question, although merely in a vague and imperfect manner.

The simple power of representing images of sense exists, as re have already said, in other animals as well as man. The power, on the contrary, of representing images for deliberation is confined to animals that reason. For the question whether this r that is to be done is work that calls for reason and reflection: and since it is the stronger and the more preferable which desire pursues, it must always measure by one standard, and so it is enabled to form one conception out of several images which represent sensations. Hence the reason why animals, while possessing the faculty of representing images of sense, are not bought to have opinion. They do not possess the kind of desire which forms itself as the conclusion of syllogism, while at the same time such deliberate desire always involves the possession of opinion: and thus their desire is destitute of any faculty of deliberation. In the case of man, however, sometimes the images of sense overcome and move the rational volition: sometimes, as in incontinence, two things in turn overcome and stir up one another, desire thus following on desire much as a ball that players toss about: but the normal and natural course is always that in which the superior force of reason is the more supreme, and stimulates to action. Thus, then, altogether there are three courses of movement possible among the springs of action: although, it should be added, the cognitive faculty is not moved, but continues permanent. Since, however, this cognitive faculty presents itself, on the one hand, as a conception and judgment about the universal, on the other hand as a conception of the particular — the one asserting that all men of such and such character should do such and such actions, the other explaining that this particular action is of this nature, and that I am an individual of the kind described — it is this latter form of opinion, rather than the universal, that stimulates to action, or it is both of them together, the one, however, more as in repose, the other in activity.


Everything that is animate and living must, from its birth to the time of its decay, possess the soul which we describe as nutritive: because whatever has been born must exhibit the phenomena of growth, maturity, and dissolution, and this it cannot do apart from food and nourishment Thus, then, the nutrient capacity must be inherent in all objects that are marked by growth and by decay.

Sensation, on the other hand, need not be present in all things that live: for neither can those objects whose body is altogether simple and uncompounded possess the sense of touch (although without this sense it is impossible to have animal life), nor again can those objects which are unable to receive the form without the matter be endowed with the capacity of sense. The animal, however, rightly so-called, must possess the powers of sense-perception, if, as we hold, nature produces nothing without a purpose, all natural objects existing for some end, or being the concomitants of objects which exist for some end. Now, if a body were supplied with faculties of movement, but did not have the power of sense-perception, it would be destroyed, and would not attain its end, which it is nature's work to realize. For how, we may ask, will such an organism provide food for itself? It is only those which are stationary that have their food supplied them from their place of origin. Nor, indeed, is it possible that a body should have soul and discriminating reason and not possess sensation, if it be capable of motion and produced by generation. Nor indeed, for that matter, will it make any difference if it be actually unbegotten. For, for what end would such a body be without the faculty of sense? It could only be because its absence would be better for it either as regards its soul or as regards its body. But, as matter of fact, the absence of sense could not possibly contribute to either. The soul will not understand the world better because it is deprived of sense: and the body will not be any more a body because it is without the sensitive capacities.

No body, therefore, not being stationary, possesses soul, without at the same time adding on the faculties of sense. If, however, it possess the faculty of sense, its body must be either simple or compound. It cannot, however, be simple: because in that case it would not have the sense of touch: and this it must necessarily possess. This, in fact, is evident from the following considerations. Since the animal is a body possessed of soul, and every body is tangible: it follows, since the tangible is perceived by touch, that the body of the living animal must be also endowed with the sense of touch, if the animal is to be able to maintain itself. For the other senses, such as smell, sight, and hearing, perceive their objects through the medium of other substances: but if an animal, when it came in contact with different substances, were not to have the sense of touch, it would not be able to avoid some and take others: and under these circumstances it would be impossible for it to preserve itself. Hence taste is, as it were, a sort of touch: for it is applied to nutriment: and nutriment is a body that can be touched. On the other hand, sound and colour and smell supply no nourishment, nor do they cause either growth or dissolution. Taste, therefore, it follows, must be a kind of touch, because it is the sense which perceives the tangible and nutritive.

These two senses, then, of taste and touch are indispensable conditions of animal life: evidently, in fact, the animal cannot possibly exist without the sense of touch. The other senses are directed towards higher ends than mere existence, and do not belong to any class of animals whatever, but only to some particular species of animal. Thus, for example, they must be possessed by the animal capable of forward movement, because the animal, if it is to be preserved, must be able to perceive an object, not only when brought into immediate contact with it, but also when it is some distance from it Now, this is only possible in case it have the power of perceiving through some intervening medium, this medium being affected and set in motion by the object of sense, while the sense itself in turn is affected by the medium. [We may illustrate by the manner in which movement is communicated.] That which produces local movement continues its effect until it makes a change and the original agent in propulsion causes another object to propel, the movement being effected through the intervening object: and just as the first object that moves propels without being propelled, whereas the last member in the chain is propelled only and does not propel, while the middle links (of which there may be many) are both propelling and propelled, so also is it with the alteration [involved in sense-perception], excepting that the alteration is effected without change of position. Thus, if one were to plunge anything in wax, the wax would be moved so far as one plunged it: a stone under similar treatment would not be moved at all, and water would be so to a still greater degree. Air, on the other hand, is moved to the greatest possible extent, and both impresses and is impressed so long as it continues still and remains a whole. And thus, also, to touch upon the theory of " repercussion," it is better to suppose that the air is affected by the colour and the form, so long as it remains unbroken (and it is so over every smooth surface), than that the visual ray after it has issued from the eyes and mixed with objects is then reflected and sent back again. Hence this air, itself affected by the object, moves in turn the eyesight, much in the same way as if the impress in the wax were to penetrate through to its extremity.


The body of the animal cannot, it is evident, consist of any one single element, such as for instance fire or air. The reason of this is that touch is the necessary pre-supposition of the other senses, because, as we have said, every animate body is also provided with the sense of touch. Now, all the other elements except earth might serve as organs of the senses, but they all effect perception only mediately. Touch, on the contrary, acts by direct contact with its objects, and from this very circumstance, in fact, derives its name: and though the other senses do also perceive by contact, yet it is by contact through a third thing: whereas touch seems to perceive by direct contact on its own part. Thus the body of the animal cannot be composed of any such element as forms the medium to the other senses. Nor yet can it be composed of earth alone. For touch applies itself as a central state to all things tangible, and its organ is fitted to receive, not only the different qualities of earth, but also of the hot and cold, and of all other tangible qualities of body. And hence it is that we have no perception through the bones and hair and such like parts, because they are composed of earth entirely. Plants, again, do not have any powers of sense-perception, because they are composed totally of earth. Apart from touch, however, no other powers of senseperception can exist: and this organ of touch is composed neither of the earth nor of any other of the elements.

It is manifest, therefore, that the absence of this sense alone must involve the animal's death: for nothing can possess this without being a living animal, nor need the animal, to be an animal, have any sense but this one. Hence the objects of the other senses — such as, for example, colour, sound, and scent — do not by their excess destroy the animal itself, but only the organ, although it may incidentally destroy the animal frame as well: as, for example, when a push and blow accompany a sound, or when what is directly seen and smelled sets in movement other forces which destroy life by their contact So also flavour may cause destruction in this manner — in so far, that is, as it is incidentally something tangible.

In the case of objects of touch, however, such as heat and cold and hardness, excess destroys [not only the sense-organ but also] the animal itself. The object of any sense, in fact, destroys, if it be developed to excess, the organ of sense: and in this same way, then, tangible objects destroy the sense of touch. But life itself is constituted by this sense, since, as has been shewn before, the animal cannot exist without the sense of touch. And thus excess in things tangible destroys not only the organ of sense but the animal itself as well, because this is the one sense absolutely essential to animal life; while as regards the other senses, the animal has them, as has been said, not for bare existence, but for the sake of higher ends. Thus, for instance, it possesses sight, so that it may see objects both in air and water, and in general in whatever is transparent. Taste, on the other hand, it possesses for the sake of discriminating the agreeable and disagreeable in food, so that it may desire and move itself accordingly. Hearing, again, it possesses so that it may convey a meaning to itself: the tongue it possesses so that it may express something or other to another.

 This work is a translation and has a separate copyright status to the applicable copyright protections of the original content.


This work was published before January 1, 1929, and is in the public domain worldwide because the author died at least 100 years ago.

Public domainPublic domainfalsefalse


This work was published before January 1, 1929, and is in the public domain worldwide because the author died at least 100 years ago.

Public domainPublic domainfalsefalse