Book I, Chapter 3

We must consider first the question of movement. For perhaps it is not only false that the essence of the soul is such as those describe who say that the soul is that which moves itself, or that which is capable of moving; it may even be among the things impossible that movement should belong to it at all. That what causes movement need not itself be moved has been said before.

Now everything that is moved is moved in one of two ways: either in virtue of something else, or in virtue of itself. By "in virtue of something else" we mean whatever is moved by being in something that is moved, as sailors are; for they are not moved in the same way as the ship. The ship is moved in virtue of itself, whereas they are moved by being in something that is moved. This is clear in the case of the bodily parts: the movement proper to feet is walking, and this belongs to men too; but it does not belong to the sailors at that time. Since, then, "being moved" is spoken of in these two ways, our present inquiry about the soul is whether it is moved in virtue of itself and partakes of movement.

There being four kinds of movement — locomotion, alteration, diminution, and growth — the soul would be moved with one of these, or with more than one, or with all. And if it is moved not accidentally, movement would belong to it by nature; and if this is so, place would belong to it as well, for all the movements mentioned take place in a place. But if the essence of the soul is to move itself, then being moved will belong to it not accidentally, as it belongs to the white or to what is three cubits long; for these too are moved, but accidentally, since what is moved is the body to which they belong. That is why they have no place of their own; but the soul will have one, if it really partakes of movement by nature.

Again, if it is moved by nature, it might also be moved by constraint; and if by constraint, then also by nature. The same holds of rest: that towards which a thing is moved by nature is also that in which it rests by nature, and likewise that towards which it is moved by constraint is that in which it rests by constraint. But what the enforced movements and rests of the soul will be, it is not easy to explain even for those who are willing to invent them.

Again, if the soul is to move upwards it will be fire, and if downwards, earth; for these are the movements of those bodies. And the same argument applies to the intermediate bodies.

Again, since the soul evidently moves the body, it is reasonable that it should move it with the very movements with which it is itself moved. And if this is so, it is also true to say, conversely, that the movement with which the body is moved is that with which the soul is moved too. But the body is moved by locomotion; hence the soul too would change its place along with the body, shifting either as a whole or in its parts. And if this is possible, it would also be possible for it to go out and enter in again; and from this it would follow that dead animals rise again.

As for accidental movement, the soul might indeed be moved by something else, since the animal may be pushed by force. But that which has self-movement in its very essence ought not to be moved by anything else, except accidentally — just as what is good in itself, or by reason of itself, ought not to be good through something else or for the sake of something else. But one would say that the soul, if it is moved at all, is moved above all by the objects of perception.

But further, even if it does move itself, it would itself be moved; so that, if all movement is a displacement of what is moved in that respect in which it is moved, the soul too would be displaced out of its essence — unless it moves itself only accidentally. But on their view the movement belongs to its very essence in virtue of itself.

Some also say that the soul moves the body in which it is in the same way as it is itself moved — Democritus, for instance, whose account is much like that of Philippus the comic dramatist. For Philippus says that Daedalus made the wooden Aphrodite move by pouring quicksilver into it. Democritus speaks in a similar way; for he says that the indivisible spheres, being in movement because it is their nature never to stay still, drag along with them and set in motion the whole body. But we shall ask whether these same spheres also produce rest. How they will do so it is difficult, or even impossible, to say. And in general the soul does not appear to move the animal in this way, but through some kind of choice and thinking.

In the same way the Timaeus too gives a physical account of the soul's moving the body: by being moved itself, it moves the body as well, because it is interwoven with it. For having compounded the soul out of the elements and divided it in accordance with the harmonic numbers — so that it might have an innate perception of harmony, and so that the whole might be carried round in concordant revolutions — he bent the straight line into a circle; and having divided the one circle into two circles joined at two points, he divided one of these again into seven circles, on the assumption that the revolutions of the heaven are the movements of the soul.

First, then, it is not well said that the soul is a magnitude. For it is clear that he means the soul of the universe to be such as what is called intellect (nous) is — certainly not such as the perceptive soul is, nor such as the appetitive; for the movement of these is not a revolution in a circle. Now the intellect is one and continuous, in the way that thinking is; and thinking consists of the thoughts. But these are one by succession, as number is, not as a magnitude is. Therefore the intellect is not continuous in that way either, but is either without parts, or at any rate not continuous in the way that some magnitude is. For how, if it were a magnitude, would it think at all — with any one of its parts whatever? Its parts must be taken either as magnitudes or as points, if a point too is to be called a part. If, then, by points, and these are infinite in number, it is clear that the intellect will never traverse them; and if by magnitudes, it will think the same thing many times, or an infinite number of times. But evidently it is possible to think a thing once only.

And if it is enough for the intellect to touch its object with any one of its parts, why must it move in a circle, or have magnitude at all? But if thinking requires that it touch with the whole circle, what is the contact effected by the parts? Again, how will it think what has parts by means of what has no parts, or what has no parts by means of what has parts?

But it must be that the intellect is this circle. For the movement of intellect is thinking, and the movement of a circle is revolution. If, then, thinking is a revolution, the circle whose revolution of this kind is thinking will be intellect. And it will always be thinking something — as it must, if the revolution is eternal. For practical thoughts have limits, since they are all for the sake of something else, while theoretical thoughts are bounded in the same way as the accounts of which they consist. And every account is either a definition or a demonstration. Now demonstrations both start from a first principle and have, in a way, as their end the deduction or the conclusion; and if they do not reach an end, at any rate they do not bend back again to the beginning, but always take in a further middle term and extreme, and so go straight forward — whereas a revolution bends back again to the beginning. And definitions are all limited.

Again, if the same revolution occurs many times, it will be necessary to think the same thing many times. Again, thinking seems to resemble a coming to rest and a halt rather than a movement, and the same holds of deduction. Nor, further, is what is not easy but constrained a blessed thing; and if the movement of the soul is not its essence, it would be moved contrary to its nature. It is laborious, too, to be mixed with the body without being able to be released from it, and moreover it is something to be shunned, if it is indeed better for the intellect not to be with a body, as is commonly said and as many agree.

The cause of the heaven's being carried round in a circle is also left unclear. For the essence of the soul is not the cause of its being carried in a circle — on the contrary, it is moved in this way accidentally — nor is the body the cause; rather the soul is the cause of movement to the body. Nor again is it said that this is better; and yet god ought to have made the soul move in a circle for just this reason, that it is better for it to be moved than to remain at rest, and better to be moved in this way than in another. But since an inquiry of this sort belongs more properly to other discussions, let us leave it aside for the present.

There is, however, an absurdity that follows both from this account and from most of the accounts of the soul. They attach the soul to a body and place it in one, without further determining for what reason this happens, or what the condition of the body is. And yet this would seem to be necessary; for it is because of their association that the one acts and the other is acted upon, and the one is moved and the other moves, and none of these relations holds between things taken at random. But they only try to say what sort of thing the soul is, and determine nothing further about the body that is to receive it — as though it were possible, as in the Pythagorean tales, for any soul whatever to clothe itself in any body whatever; for each body seems to have its own proper form and shape. What they say is much like saying that the art of carpentry could clothe itself in flutes; for the art must use its own tools, and the soul its own body.