by Aristotle
2 · For our study of soul it is necessary, while formulating the problems of [20] which in our further advance we are to find the solutions, to call into council the views of those of our predecessors who have declared any opinion on this subject, in order that we may profit by whatever is sound in their suggestions and avoid their errors.
The starting-point of our inquiry is an exposition of those characteristics which have chiefly been held to belong to soul in its very nature. Two characteristic marks have above all others been recognized as distinguishing that which has soul in it [25] from that which has not—movement and sensation. It may be said that these two are what our predecessors have fixed upon as characteristic of soul.
Some say that what originates movement is both pre-eminently and primarily [30] soul; believing that what is not itself moved cannot originate movement in another, they arrived at the view that soul belongs to the class of things in movement. This is what led Democritus to say that soul is a sort of fire or hot substance; his ‘forms’ or [404a1] atoms are infinite in number; those which are spherical he calls fire and soul, and compares them to the motes in the air which we see in shafts of light coming through windows; the mixture of seeds of all sorts he calls the elements of the whole [5] of nature (Leucippus gives a similar account); the spherical atoms are identified with soul because atoms of that shape are most adapted to permeate everywhere, and to set all the others moving by being themselves in movement. This implies the view that soul is identical with what produces movement in animals. That is why, further, they regard respiration as the characteristic mark of life; as the environment [10] compresses the bodies of animals, and tends to extrude those atoms which impart movement to them, because they themselves are never at rest, there must be a reinforcement of these by similar atoms coming in from without in the act of respiration; for they prevent the extrusion of those which are already within by [15] counteracting the compressing and consolidating force of the environment; and animals continue to live only so long as they are able to maintain this resistance.
The doctrine of the Pythagoreans seems to rest upon the same ideas; some of them declared the motes in air, others what moved them, to be soul. These motes [20] were referred to because they are seen always in movement, even in a complete calm.
The same tendency is shown by those who define soul as that which moves itself; all these seem to hold the view that movement is what is closest to the nature of soul, and that while all else is moved by soul, it alone moves itself. This belief arises from their never seeing anything originating movement which is not first itself moved.
[25] Similarly also Anaxagoras (and whoever agrees with him in saying that thought set the whole in movement) declares the moving cause of things to be soul. His position must, however, be distinguished from that of Democritus. Democritus roundly identifies soul and mind, for he identifies what appears with what is true—that is why he commends Homer for the phrase ‘Hector lay with thought distraught’;1 he does not employ mind as a special faculty dealing with truth, but [404b1] identifies soul and thought. What Anaxagoras says about them is less clear; in many places he tells us that the cause of beauty and order is thought, elsewhere that it is soul; it is found, he says, in all animals, great and small, high and low, but [5] thought (in the sense of intelligence) appears not to belong alike to all animals, and indeed not even to all human beings.
All those, then, who had special regard to the fact that what has soul in it is moved, adopted the view that soul is to be identified with what is eminently originative of movement. All, on the other hand, who looked to the fact that what has soul in it knows or perceives what is, identify soul with the principle or principles [10] of Nature, according as they admit several such principles or one only. Thus Empedocles declares that it is formed out of all his elements, each of them also being soul; his words are:
For ’tis by Earth we see Earth, by Water Water,
By Ether Ether divine, by Fire destructive Fire,
By Love Love, and Hate by cruel Hate.2 [15]
In the same way Plato in the Timaeus3 fashions the soul out of his elements; for like, he holds, is known by like, and things are formed out of the principles or elements. Similarly also in the lectures ‘On Philosophy’ it was set forth that the Animal-itself is compounded of the Idea itself of the One together with the primary length, [20] breadth, and depth, everything else being similarly constituted. Again he puts his view in yet other terms: Mind is the monad, science or knowledge the dyad (because it goes undeviatingly from one point to another), opinion the number of the plane, sensation the number of the solid; the numbers are by him expressly identified with the Forms themselves or principles, and are formed out of the elements; now things [25] are apprehended either by mind or science or opinion or sensation, and these same numbers are the Forms of things.
Some thinkers, accepting both premisses, viz. that the soul is both originative of movement and cognitive, have compounded it of both and declared the soul to be a self-moving number.
As to the nature and number of the first principles opinions differ. The [30] difference is greatest between those who regard them as corporeal and those who regard them as incorporeal, and from both dissent those who make a blend and [405a1] draw their principles from both sources. The number of principles is also in dispute; some admit one only, others assert several. There is a consequent diversity in their several accounts of soul; they assume, naturally enough, that what is in its own nature originative of movement must be among what is primordial. That has led some to regard it as fire, for fire is the subtlest of the elements and nearest [5] to incorporeality; further, in the primary sense, fire both is moved and originates movement in all the others.
Democritus has expressed himself more ingeniously than the rest on the grounds for ascribing each of these two characters to soul; soul and thought are, he says, one and the same thing, and this thing must be one of the primary and [10] indivisible bodies, and its power of originating movement must be due to its fineness of grain and the shape of its atoms; he says that of all the shapes the spherical is the most mobile, and that this is the shape of the particles of both fire and thought.
Anaxagoras, as we said above, seems to distinguish between soul and thought, but in practice he treats them as a single substance, except that it is thought that he [15] specially posits as the principle of all things; at any rate what he says is that thought alone of all that is is simple, unmixed, and pure. He assigns both characteristics, knowing and origination of movement, to the same principle when he says that it was thought that set the whole in movement.
Thales, too, to judge from what is recorded about him seems to have held soul [20] to be a motive force, since he said that the magnet has a soul in it because it moves the iron.
Diogenes (and others) held the soul to be air because he believed air to be finest in grain and a first principle; therein lay the grounds of the soul’s powers of knowing and originating movement. As the primordial principle from which all other things are derived, it is cognitive; as finest in grain, it has the power to originate movement.
[25] Heraclitus too says that the first principle—the ‘warm exhalation’ of which, according to him, everything else is composed—is soul; further, that this exhalation is most incorporeal and in ceaseless flux; that what is in movement requires that what knows it should be in movement; and that all that is depends on movement (herein agreeing with the majority).
Alcmaeon also seems to have held a similar view about soul; he says that it is [30] immortal because it resembles the immortals, and that this immortality belongs to it in virtue of its ceaseless movement; for all the divine things, moon, sun, the [405b1] planets, and the whole heavens, are in perpetual movement.
Of more superficial writers, some, e.g. Hippo, have pronounced it to be water; they seem to have argued from the fact that the seed of all animals is fluid, for Hippo tries to refute those who say that the soul is blood, on the ground that the seed
, which is the primordial soul, is not blood.
[5] Another group (Critias, for example) did hold it to be blood; they take perception to be the most characteristic attribute of soul, and hold that perceptiveness is due to the nature of blood.
Each of the elements has thus found its partisan, except earth—earth has found no supporter unless we count as such those who have declared soul to be, or to [10] be compounded of, all the elements. All, then, it may be said, characterize the soul by three marks, Movement, Sensation, Incorporeality, and each of these is traced back to the first principles. That is why (with one exception) all those who define the soul by its power of knowing make it either an element or constructed out of the [15] elements. The language they all use is similar; like, they say, is known by like; as the soul knows everything, they construct it out of all the principles. Hence all those who admit but one cause or element, make the soul also one (e.g. fire or air), while those who admit a multiplicity of principles make the soul also multiple. The [20] exception is Anaxagoras; he alone says that thought is impassible and has nothing in common with anything else. But, if this is so, how or in virtue of what cause can it know? That Anaxagoras has not explained, nor can any answer be inferred from his words. All who acknowledge pairs of opposites among their principles, construct the soul also out of these contraries, while those who admit as principles only one [25] contrary of each pair, e.g. either hot or cold, likewise make the soul some one of these. That is why they allow themselves to be guided by the names; those who identify soul with the hot argue that ζῆν (to live) is derived from ζεῖν (to boil), while those who identify it with the cold say that soul (ψυχή) is so called from the process [30] of respiration and refrigeration (κατάψυξις).
Such are the traditional opinions concerning soul, together with the grounds on which they are maintained.
3 · We must begin our examination with movement; for, doubtless, not only is it false that the essence of soul is correctly described by those who say that it is what moves (or is capable of moving) itself, but it is an impossibility that movement [406a1] should be even an attribute of it.
We have already4 pointed out that there is no necessity that what originates movement should itself be moved. There are two senses in which anything may be moved—either indirectly, owing to something other than itself, or directly, owing to [5] itself. Things are indirectly moved which are moved as being contained in something which is moved, e.g. sailors, for they are moved in a different sense from that in which the ship is moved; the ship is directly moved, they are indirectly moved, because they are in a moving vessel. This is clear if we consider their limbs; the movement proper to the legs (and so to man) is walking, and in this case the sailors are not walking. Recognizing the double sense of ‘being moved’, what we [10] have to consider now is whether the soul is directly moved and participates in such direct movement.
There are four species of movement—locomotion, alteration, diminution, growth; consequently if the soul is moved, it must be moved with one or several or all of these species of movement. Now if its movement is not incidental, there must be a movement natural to it, and, if so, as all the species enumerated involve place, place [15] too must be natural to it. But if the essence of soul be to move itself, its being moved cannot be incidental to it, as it is to what is white or three cubits long; they too can be moved, but only incidentally—what is moved is that of which white and three cubits long are the attributes, the body in which they inhere; hence they have no [20] place: but if the soul naturally partakes in movement, it follows that it must have a place.
Further, if there be a movement natural to the soul, there must be a counter-movement unnatural to it, and conversely. The same applies to rest as well as to movement; for the terminus ad quem of a thing’s natural movement is the place of its natural rest, and similarly the terminus ad quem of its enforced [25] movement is the place of its enforced rest. But what meaning can be attached to enforced movements or rests of the soul, it is difficult even to imagine.
Further, if the natural movement of the soul be upward, the soul must be fire; if downward, it must be earth; for upward and downward movements are the characteristics of these bodies. The same reasoning applies to the intermediate movements, termini, and bodies. Further, since the soul is observed to originate [30] movement in the body, it is reasonable to suppose that it transmits to the body the movements by which it itself is moved, and so, reversing the order, we may infer from the movements of the body back to similar movements of the soul. Now the [406b1] body is moved by locomotion. Hence it would follow that the soul too must change either its place as a whole or the relative places of its parts. This carries with it the possibility that the soul might even quit its body and re-enter it, and with this would be involved the possibility of a resurrection of animals from the dead. But, it may be contended, the soul can be moved indirectly by something else; for an animal can be [5] pushed out of its course. Yes, but that to whose essence belongs the power of being moved by itself, cannot be moved by something else except incidentally, just as what is good by or in itself cannot owe its goodness to something external to it or to some end to which it is a means.
[10] If the soul is moved, the most probable view is that what moves it is sensible things.
We must note also that, if the soul moves itself, it must be the mover itself that is moved, so that it follows that if movement is in every case a displacement of that which is in movement, in that respect in which it is said to be moved, the movement of the soul must be a departure from its essential nature, at least if its self-movement [15] is essential to it, not incidental.
Some go so far as to hold that the movements which the soul imparts to the body in which it is are the same in kind as those with which it itself is moved. An example of this is Democritus, who uses language like that of the comic dramatist Philippus, who accounts for the movements that Daedalus imparted to his wooden [20] Aphrodite by saying that he poured quicksilver into it; similarly Democritus says that the spherical atoms owing to their own ceaseless movements draw the whole body after them and so produce its movements. We must urge the question whether it is these very same atoms which produce rest also—how they could do so, it is difficult and even impossible to say. And, in general, we may object that it is not in this way that the soul appears to originate movement in animals—it is through [25] intention or process of thinking.
It is in the same fashion that the Timaeus tries to give a physical account of how the soul moves its body; the soul, it is there said, is in movement, and so owing to their mutual implication moves the body also. After compounding the soul-substance out of the elements and dividing it in accordance with the harmonic [30] numbers, in order that it may possess a connate sensibility for ‘harmony’ and that the whole may move in movements well attuned, the Demiurge bent the straight line into a circle; this single circle he divided into two circles united at two common [407a1] points; one of these he subdivided into seven circles. All this implies that the movements of the soul are identified with the local movements of the heavens.
Now, in the first place, it is a mistake to say that the soul is a magnitude. It is evident that Plato means the soul of the whole to be like the sort of soul which is [5] called thought—not like the sensitive or the desiderative soul, for the movements of neither of these are circular. Now thought is one and continuous in the sense in which the process of thinking is so, and thinking is identical with thoughts—these have a serial unity like that of number, not a unity like that of a magnitude. Hence thought cannot have that kind of continuity either; thought is either without parts or is continuous in some other way than that which characterizes a magnitude. [10] How, indeed, if it were a magnitude, could thought possibly think? Will it think with any one indifferently of its parts? In this case, the ‘part’ must be understood either in the sense of a magnitude or in the sense of a point (if a point can be called a part of a magnitude). If we accept the latter alt
ernative, the points being infinite in number, obviously thought can never exhaustively traverse them; if the former, thought must think the same thing over and over again, indeed an infinite number of times (whereas it is manifestly possible to think a thing once only). If contact of [15] any part whatsoever of itself with the object is all that is required, why need thought move in a circle, or indeed possess magnitude at all? On the other hand, if contact with the whole circle is necessary, what meaning can be given to the contact of the parts? Further, how could what has no parts think of what has parts, or what has parts think of what has none? We must identify the circle referred to with thought; for it is thought whose movement is thinking, and it is the circle whose movement is [20] revolution, so that if thinking is a movement of revolution, the circle which has this characteristic movement must be thought.5