Lecture 6 — Soul as a self-moving substance

The first thing to be considered is movement. For perhaps it is not only false to say that this is the substance of the soul, as some mean when they say the soul is self-moving, or is able to move itself, but that there should be movement in it at all is an impossibility.

It has already been stated that it is not necessary that everything that causes motion be itself moving. For everything moves in one of two ways: either in virtue of another, or in virtue of itself.

We say “in virtue of another” of anything that is moving through being in that which is moving, like sailors; for these are not in motion in the same way as the ship. The latter is moving according to its very self, but they are through being in what is moving. This is evident if we consider their parts. Walking belongs to the feet in a prior way, but this also belongs to men; but this is not how it is for the sailors. To be moving being so predicated in two ways, we now turn to the soul, asking whether it moves through itself and participates in motion.

Since there are four motions (change of place, alteration, increase, and decrease), its motion must be one of these, or some, or all. But if its movement is not accidental, then motion will be in it by nature: and if so, it so will place, for all the aforesaid movements are in place.

If it is the substance of the soul to move itself, to be in motion will not be in it accidentally, as it is for what is white or three cubits long; for these also move, but accidentally. For what is moved is the body in which these inhere; hence, place does not belong to them but to the soul, if indeed it naturally participates in motion.

Further, if it moves by nature, it will also move by force; and if by force, then, by nature. And its rest will be in the same way. For whithersoever it moves by nature, there it will come to rest by nature; and likewise, wheresoever it is moved by force, there it will come to rest by force. But what kind of enforced motions and rests will there be in the soul? To find an answer is not easy, nor even to imagine one.

Again, if it moves upwards, it will be fire, and if downwards, earth; for such are the movements of these bodies; and the same holds of the intermediate elements.

Since it seems to move the body, it would seem reasonable to say that it does so by the same motions as those by which it is moved itself. If so, then it is true to say, conversely, that just as the body moves, the soul also moves. Now, the body moves by change of place; hence the soul too will change in accordance with the body, either the whole or the parts being carried forth. If this is so, then it might happen that after leaving the body it could return to it. And it would follow that dead animals could rise again.

If it does move, however, by something else, its motion will be accidental; for certainly an animal can be driven by force. But what has self-movement of its substance cannot be moved by another, save accidentally, as that which is good in itself or for its own sake cannot exist for the sake of another, or on account of another.

One might certainly say that, if the soul is moved at all, it is moved by the objects of sensation.

But if it moves itself, it also is in motion. Hence if all motion is a displacement from that which is moved inasmuch as it is moved, then the soul must be displaced from its own substance by itself, unless it moves itself accidentally; but this is a self-movement of its substance.

68. The first thing to be considered (405b31). The Philosopher now begins to criticize the theories he has been recounting. These theories amount to three statements about the soul: that it is the principle of movement, that it is the principle of knowledge, and that it is most incorporeal or finest. The two former attributions, the principal ones—that it is the principle of motion and that it is the principle of knowledge—they attribute to the soul primarily and through itself. The third—that it is finest—is said well in one sense and said badly in another. For if “finest” is taken as predicated simply of the soul, then it is well said, for soul is without a doubt the most incorporeal and finest thing. But if it is predicated not simply but along with the body, as if to say that soul is the finest body, then it is said badly. Hence the Philosopher sets to work only with the two former attributions of movement and of knowledge, which are said of the soul through itself.

69. This part of the treatise falls into three divisions.

Aristotle first argues against the philosophers who had made the soul the principle of movement;

second, at there are, then, three ways (409b18; [178]), against those who regarded it as the principle of knowledge;

and third, at since knowledge does belong to the soul (411a26; [199]), he raises a question whether movement, sensing, and knowing ought to be attributed to the soul as to one principle or several.

The first of these divisions is again divided.

He first adduces objections against simply identifying the soul itself with a source of movement;

second, against an opinion proceeding from this identification, according to which the soul was also a self-moving number. This comes at by far the most unreasonable (408b32; [168]).

The former argument again subdivides into two:

first, a criticism of the way in which these philosophers had predicated movement of the soul, inasmuch as they attribute movement to the soul itself;

and second, at one might with more reason (408a34; [146]), a query whether this predication might have been made differently.

Then the criticism is divided into two:

first, a general argument against all who said that the soul was the source of movement;

and second, at some say that a soul moves (406b15; [87]), a series of particular discussions of special points.

Finally, the general argument is subdivided.

First, he says what he intends to do;

second, he argues in support of his own opinion, at since there are four motions (406a12; [75]).

70. He begins then by remarking that philosophers have studied the soul from two points of view, from motion and from sensation. This is clear from what has been said. (Lect. 3, n. 32.) And Aristotle says that he will start from movement (405b31).

Now, all the other philosophers who came to know the soul from motion had one principle in common, namely, that everything that produces movement is itself in motion. They thought, therefore, that if soul is by nature a cause of movement, the soul has this from its own substance. So they put movement into its definition, calling it something that moves its very self.

71. Now, here there are two disputable points, the reasoning of the position and the position itself, for each of these is false. For both the argument for their position and their position is false. For they supposed something as true through itself—that everything that moves another is moving—when it is false, as is clearly enough shown in Physics 8, where Aristotle proves the existence of an immobile mover. (Aristotle, Physics 8.5–6, 10; cf. Aquinas, Commentary on Physics, bk. 8, lect. 9, 12, 22.)

And as to this, we may give here a short proof: for if something that produces movement is also moving, it is certain that insofar as it produces movement, it is in act, and insofar as it is moving, it is in potency. And thus the same thing would be in act and potency in the same respect, which is incongruous.

72. But even setting this difficulty aside, the position that the soul is in movement is disputable. Its upholders indeed added the further proposition, that movement was of the soul’s substance; but Aristotle denies both, where he says, for perhaps. He puts it like this because he has not yet proved his assertion, namely, that it is not only false to say that movement is of the substance of the soul (which is what they imply when they say the soul is self-moving or is able to move itself) but that it is also quite impossible that the soul should move at all.

73. That not everything which causes movement need itself be moving was already stated in an earlier work, book 8 of the Physics. Now, in any self-mover there are two things to be considered, the thing moving and the thing moved; and the former cannot through itself be the same as the latter. In animals, however, though the moving part is not in motion through itself, yet it is in motion accidentally.

For everything that is in motion moves in two ways, either in virtue of another or in virtue of itself: in virtue of another, or accidentally, when it is not itself moving but that in which it is, is moving, just as the sailor is moving not because he himself is moving, but because the ship is moving; hence, this, the ship, moves virtue of itself, but the sailor only accidentally. And that this sailor is not moving through himself is clear, since when someone is moving through himself, he is moving in virtue of his own parts, as in someone walking, walking belongs to the feet in a prior way; but when the sailor is on a ship, this is not how it is. Movement, then, can be taken in either of these two ways, in through itself and accidentally; but since the philosophers we are discussing said that the soul moves through itself, we can forgo at present the question whether it moves accidentally, and consider only whether it moves through itself and participates in motion, as they maintained.

74. To show that the soul does not move through itself, Aristotle uses six arguments.

With regard to which, we should note that, while the arguments may not appear strong, still they are effective in relation to the position he is criticizing. For one should argue in one way for one who intends to find the truth simply speaking, since one must proceed from true things, but one who is arguing against a position proceeds from the things granted. Hence it is that when Aristotle criticizes the positions, he often seems to use rather weak arguments. In each case, he is, in fact, using appropriately effective arguments because, to destroy the position, he is proceeding from the things granted.

75. The first argument begins at since there are four motions (406a12) and may be stated as follows. If the soul moves, its movement is either through itself or accidentally.

If accidentally, then it is not of the substance of the soul (which is against their opinion); rather, the soul moves in the same way as whiteness or three cubits, which move only accidentally, and they themselves do not need place for this.

But if the soul moves through itself, it moves in one of the four species of movement: change of place, growth, decrease, or alteration. (For coming-to-be and passing-away are not movements, properly speaking, but changes.) Hence the soul will have to move in one of these four species—in reference to place; by increase or decrease; or by an alteration. But if it moves in one of these and all these movements occur in place, the soul will then also be in a place.

76. There seem to be two doubtful points in this argument.

The first is that, while it is clear enough that locomotion, growth, and decrease occur in a place, it suggests a difficulty about alteration. Some meet this difficulty by saying that as only bodies are subject to alteration, and all bodies are in place, alteration itself may be said to occur in place. But this does not keep to the letter of the argument: Aristotle says that this kind of movement is in place and not merely according to place. And therefore one should say that alteration certainly occurs in place, for motion in a place is something other than motion according to place. But alteration is not according to place, but it is in place, for in an alteration the agent producing it must draw near to the thing being altered; otherwise, nothing would ever be altered. And since drawing near is a local movement, it follows that local motion is present there as its cause.

77. The second difficulty is that these philosophers do not in fact see anything incongruous in the soul’s being in place, since they maintain that it moves through itself. So Aristotle’s objection seems not strong. To this, two answers might be given: in one way, that the incongruity of the soul’s being in place will become clearer in subsequent arguments; and in another way, because this is why it is incongruous: if the soul were in place, it would have to be assigned a proper and separate place within the body, and thus would not be the form of the whole body.

78. The second argument, at further, if it moves (406a22), is this. If the soul moves through itself according to place, the movement must be natural to it. But anything that moves naturally is also moved by force. Now, its natural movement implies a natural rest, and if it comes to rest naturally, it comes to rest by force. Therefore the soul moves by force and rests by force. But this is impossible, since the soul’s motions and rests are voluntary.

79. A difficulty here seems to be with the claim that what is moved naturally is also moved by force; for the heavens move naturally but not by force. I answer that the position is in truth false but, relative to the position, it is true. For these philosophers maintained that the only bodies that moved with a natural movement were the four elements, in which we do observe enforced movement and rest. This opinion is presupposed by the argument.

80. The third argument, at again, if (406a27), runs as follows: these who ascribe movement to the soul and to the body only as derived from the soul, also say that this movement is due to one or other of the elements, fire or earth or one of the intermediates. But if the soul participates in the motion of fire, it will only rise; if in that of earth, it will only sink; whereas in fact it moves in all directions. This argument is by supposition.

81. The fourth argument comes at since it seems (406a30). It is this. You say that it is in moving the body that the soul moves. It would seem reasonable, then, to say that it moves the body by its own movements; and conversely, that it is moved by the same motions which move the body. But the body is moved by change of place; so also, then, the soul. But if the soul’s local movements affect the body, the soul might, after leaving the body, enter it once more. And since it is the soul’s entrance into the body that gives life to the body, it follows that dead animals might, even naturally, rise again, which is impossible.

82. Against this argument some have objected that it ignores the difference between the movements which affect the soul itself and those by which it moves other things, including the body. The former are movements of appetite and will; not so the latter.

But in reply, one may say that to desire and to will and so on are not movements of the soul but its activities. Movements and activities differ in that movement is an act of something incomplete, whereas an activity is an act of something complete. Still, what Aristotle says is true relative to the position under discussion, for they said the soul is mobile only insofar as it moves the body.

83. But is it true that if the soul had local movement dead animals would come to life again? One should say that some have maintained that the soul pervades the whole body and is united according to some kind of proportion, and that it is not separated unless this proportion is destroyed; so according to them, the conclusion would not follow. But it does follow from the opinion of those who say the soul is located in the body as in a place or a vessel, (Themistius, In De anima, f. 5vb3.) which it sometimes enters and sometimes leaves.

84. The fifth argument comes at if it does move (406b5), and it runs as follows. It is clear that when anything belongs to something through itself, its presence in the latter is not through something else, except maybe accidentally. If, then, motion is present in the soul through itself and according to its own nature, it is necessary that the soul is mobile in virtue of itself, so it does not need to be moved through or by anything else. But we see that it is in fact moved by sensible things when it senses, and by desirable things when it desires; therefore, it does not move through itself.

85. The Platonists meet this argument by denying that the soul is moved by sensible things; these, they say, are merely involved in the soul’s own movement when it passes from one object to another.

But this is false. As Aristotle proves, the potential intellect is brought into act through them, that is, through the species of sensible realities, so it must be moved by them in this way.

86. The sixth argument begins at but if it moves itself (406b11). Clearly, if the soul moves itself, it will be in motion according to its own substance. But in every movement, the moving thing comes away or proceeds from that which moves it and inasmuch as it is moved; for instance, if anything is moved by a quantity, it departs and proceeds from that quantity. If, then, the soul is moved by its own substance and by itself (as they say), it must be displaced or proceed from its own substance, which is as much as to say that it causes its own destruction. How then could it be through movement itself that the soul becomes god-like and immortal, as some philosophers whom we have mentioned supposed? (Lect. 5, n. 61.)

This argument bears against those who did not distinguish between movement and activity. For activity does not make a displacement, but rather it completes the one acting, whereas in motion there must be a departure.