LECTURE 11 (258 a 6-b 9)

HOW THE PARTS OF A SELF-MOVER ARE RELATED TO EACH OTHER, AND HOW THE WHOLE IS SAID TO MOVE ITSELF WITH RESPECT TO THEM

1062. After the Philosopher has shown that a self-mover is divided into two parts, of which one part moves and is not moved, and the other is moved, here he shows how such parts are related to each other.

             Concerning this he makes three points. First he states his intention. Secondly, where he says, 'Thus let A . . .' (258 a 9), he proves his position. Thirdly, where he says, 'From what has been . . .' (258 b 4), he draws his main conclusion from all of the above.

             He says, therefore, first that there are two types of movers; namely, a mover which is also moved by another, and a mover which is immobile. And again, there are two types of mobile objects; namely, a mobile object which also moves, and a mobile object which moves nothing. Hence it must be said that a self-mover is composed of two parts, one of which so moves that it is immobile, and the other is so moved that it does not move.

             The term 'necessarily' (258 a 8), which he adds, can be understood in two ways. If it is understood that the moved part of a self-mover does not move something which is part of the self-mover, then the text should be read such that 'necessarily' remains affirmative and modifies 'does not . . . impart motion' (258 a 8). For he proves immediately the impossibility of there being, in that which primarily moves itself, a third part which is moved by the moved part. But if it is understood that the moved part does not move something extrinsic, then the term 'necessarily' becomes negated. For the moved part of a self-mover does not necessarily move something extrinsic. However this is not impossible.

             1063. He next shows how this occurs where he says, 'Thus let A . . .' (258 a 9).

             Concerning this he makes two points. First he proves his position. Secondly, where he says, 'Here a difficulty . . .' (258 a 27), he answers a difficulty.

             Concerning the first part he makes two points. First he shows how the parts of a self-mover are related to each other. Secondly, where he says, 'If, then, that which . . .' (258 a 21), he explains how a whole is said to move in respect to these parts.

             Concerning the first part he makes two points. First he shows that in a self-mover there are only two parts, one of which moves and is not moved, and the other of which is moved and does not move. Secondly, where he says, '. . . and each of these two . . .' (258 a 20), he explains how these two parts are joined to each other.

             He explains the first part as follows. Let it be granted that the moved part of a self-mover moves something else which is part of the same self-mover. Let the first part of the self-mover be A, which is an immobile mover. Let the second part be B, which is moved by A, and which moves a third part, C, which is so moved by B that nothing else moves which is part of the self-mover. Now it cannot be said that there is a descent to infinity with respect to the parts of a self-mover, that is, that a moved part in turn moves another. For thus it would move itself to infinity, which is impossible, as was shown above. There will be some part of the self-mover which is moved but does not move. This we call C. And although there may be many intermediaries which move and are moved, there must be a last thing moved, which is C. In the place of all the intermediaries let there be one, namely, B. Therefore this whole, which is ABC, moves itself. If the part C is removed from the whole, AB will still move itself. For one part of it is the mover, that is, A, and the other is moved, that is, B, and that is what is required for a thing to move itself, as was explained above. But C will not move itself or any other part, according to what was assumed.

             Likewise, BC does not move itself without A. For B does not move except insofar as it is moved by another, namely, A, which is not part of it. Hence it follows that only AB moves itself primarily and per se.

             And so it is necessary that a self-mover has two parts, one of which is an immobile mover, and the other of which is a moved part which cannot move anything which is a part of the self-mover. This conclusion follows from the previous argument.

             And he adds that the moved part 'does not necessarily move anything else' (258 a 19). For the moved part of a self-mover does not necessarily move some other extrinsic thing.

             1064. Next where he says, '. . . and each of these two . . .' (258 a 20), he shows how these two parts are related to each other.

             It must be noted that Aristotle has not yet proven that the first mover does not have any magnitude. He will prove this below. For certain of the ancient philosophers held that there is no substance without magnitude. Hence Aristotle, leaving this open to question before he proves it, as is his custom, says that the two parts of the self-mover, one of which is the mover and the other of which is moved, must be joined in some way because they are parts of one whole. But this is not a union by continuity. For he has said above that a self-mover and that which is moved cannot be continuous, but must be separated. Hence it follows that these two parts must be joined by contact, either in such a way that both parts touch each other, if both parts have magnitude, or such that only one part is touched by the other, and not vice versa, which is the case if the mover has no magnitude. For that which is incorporeal can touch a body by its own power of moving it, but it is not touched by the body. Two bodies, however, touch each other.

             1065. Next where he says, 'If, then, that which . . .' (258 a 21), he explains why a whole is said to move itself when one part moves and the other is moved.

             Let us suppose for the present that each part is continuous, that is, each has magnitude. For it was proven in Book VI that whatever is moved is continuous. And let us now assume the same thing in regard to the mover, before the truth is established.

             Granting this assumption, three things, namely, to be moved, to move, and to move itself, are attributed to the whole which is composed of two things. Now 'to move itself' is attributed to it, not because some part moves itself, but because the whole moves itself. And 'to move' and 'to be moved' are attributed to the whole by reason of its parts. For the whole neither moves nor is moved. Rather the part A moves, and the part B is moved. For it was already shown that there is no third part, C, which is moved by B. This is impossible if we take that which moves itself primarily, as was explained above.

             1066. Next where he says, 'Here a difficulty . . .' (258 a 27), he raises a certain question about the foregoing. First he raises the question, and secondly he answers it, where he says, 'Perhaps we may state . . .' (258 a 32).

             This question arises from what was proven above; namely, in that which moves itself primarily there are only two parts, of which one moves and the other is moved. If there were a third, then when it is removed, that which is composed of the first two parts moves itself. And thus this latter is the first self-mover.

             From this arises the following difficulty. Let us assume that the part of the self-mover which is an immobile mover, namely, A, is a continuum. From what was said before, it is clear that the part which is moved, namely, B, is a continuum. Every continuum, however, is divisible. The problem, then, is as follows: if some part is subtracted by division from A or from B, does the remaining part move or be moved? If this remaining part moves or is moved, then a part of AB moves itself. Hence, AB does not move itself primarily. And it follows further that nothing moves itself primarily.

             1067. Next where he says, 'Perhaps we may state . . .' (258 a 32), he answers this difficulty.

             It must be noted that Aristotle has proven in Book VI that in motion there is no first either in respect to the mobile object or in respect to the time or in respect to that in which motion occurs, especially in increase and in local motion. This is so because he was then speaking about motion in general and about mobile objects insofar as they are continuous, not yet applying his remarks to determinate natures. And according to this it would follow that there is not something which is moved primarily, and consequently there is not something which moves primarily, if the mover is a continuum. Thus there would also not be something which moves itself primarily. But now Aristotle is speaking about motion by applying it to determined natures. Therefore, he holds that there is something which moves itself primarily.

             He answers the foregoing difficulty as follows. Nothing prevents a continuum from being divisible in potency. Now the mover and the moved are either each continuous or at least one of them is, namely, that which is moved, which must be a continuum. Nevertheless it is possible that a continuum, whether it be the mover or the moved, have such a nature that it cannot be actually divided, as is clear in regard to the body of the sun. And if it happens that a continuum is divided, it will not retain the same potency to move or be moved which it had before. For such a potency follows from some form. A natural form, however, requires a determined quantity. Hence, if a body is incorruptible, it cannot be divided in act. If, however, it is corruptible, and if it is divided in act, it will not retain the same potency, as is clear in regard to the heart. Hence, there is nothing to prevent a first among things which are divisible in potency.

             1068. Next where he says, 'From what has been said . . .' (258 b 4), he draws his main conclusion from all of the foregoing.

             He says that it is clear from the above that there must be a first immobile mover. For since movers and things moved by another do not go on to infinity, it is necessary to stop at some first which is either immobile or a self-mover. It makes no difference whether movers and things moved stop at a first immobile mover or at some first thing which moves itself. In either case there is a first immobile mover, for in a self-mover one part is an immobile mover, as has now been shown.