LECTURE 4 (252 b 7-253 a 21)

HE ANSWERS ARGUMENTS WHICH SEEM TO PROVE THAT MOTION IS NOT ETERNAL

             997. After the Philosopher has given arguments to prove that motion is eternal, he intends here to answer possible objections to the contrary.

             Concerning this he makes two points. First he gives the arguments. Secondly, where he says, 'Of these objections . . .' (252 b 29), he answers them.

             Concerning the first part he gives three arguments and states his intention. He says that it is not difficult to answer possible objections to the contrary.

             From three arguments it seems indeed to follow that motion began to be at some time before which it did not exist at all. The first of these is that no mutation is infinite, which he proved above in Book VI. With the same argument it can be proven that no mutation is eternal.

             No terminated mutation is eternal, just as it is not infinite. But every mutation is terminated. For every mutation is naturally from something to something, and these two are contraries. And so the termini of every mutation must be the contraries between which the change occurs. But since contrariety of the termini is not clear in every local motion, he adds that it is common to all motion that nothing is moved to infinity. For nothing is moved to that which it cannot attain, as was said in Book VI. Therefore, it is clear that no mutation is eternal, just as it is not infinite. Hence, if no mutation is eternal, it seems to be possible to designate a time in which there is no mutation. This first argument deals with motion.

             998. The second argument deals with the mobile object and is given where he says, 'Secondly, we see . . .' (252 b 12).

             If motion cannot come to be anew before which it was not, it seems consistent to say of anything that it either is always moved or is never moved. For if in regard to one mobile object it is possible that there is sometimes motion and sometimes not, this argument applies equally to the whole universe. But we see that it is possible for a thing to be moved which before was not moved either in respect to the whole or in respect to one of its parts. For example, this is clear in inanimate things in which a mobile object begins to be moved, although before neither the whole nor a part was moved. Rather it was totally at rest. It follows, therefore, that in the whole universe there can be motion which before was not.

             999. But although in inanimate things it is clear that motion begins anew in something, with no motion pre-existing in that same being, nevertheless, it is clear that motion pre-exists in some exterior being by which it is moved. The third argument, therefore, deals with animals, which are not moved by an extrinsic being, but by themselves. He gives this argument where he says, 'Thirdly, the fact . . .' (252 b 17).

             That motion begins when before it was not is much more apparent in animate things than in inanimate things. For when we have been at rest for some time, with no motion existing in us, we begin at some time to be moved. The principle of our motion is from ourselves, even if nothing extrinsic should move. In inanimate beings this does not occur. Rather some extrinsic being always moves them, either by generating, or by removing an obstacle, or by imparting violence. It follows from this that if an animal is at some time completely at rest, then in some immobile being motion begins to be when before it was not, and this occurs not by some extrinsic thing which moves, but by the very thing which is moved. And if this can occur in an animal, it seems that there is nothing to prevent the same thing from happening in the universe. For an animal, and especially man, has a certain similarity to the universe. Hence it is said by some that man is a little world. And so, if in a little world motion begins when before it was not, it seems that the same thing can also occur in the large world. And if this happens in the world, it can also happen in an infinite whole, which some posit outside the world, provided that there is an infinite which can be moved and be at rest.

             1000. Next where he says, 'Of these objections . . .' (252 b 29), he answers the above arguments in order.

             In answering the first argument he says that it is correct to assert that motion between contraries cannot endure as one and the same in number. Perhaps this is necessary, as he will prove below. Since this has not yet been proven, he leaves it open to question. But someone might say that even motion between contraries can always be one in number because of the identity of a mobile object which is moved back and forth from contrary to contrary. For example, a thing is moved first from white to black, and then from black to white, and so forth. He adds, therefore, that it is impossible for the motion of one and the same mobile object to be always one and the same through repetition. And he explains this with an example. Suppose that a harp string is in a situation of this kind, and the mover who plays the harp is in a similar situation in moving. There is a problem as to whether two strokes on one harp string are one and the same motion and sound, or whether they are always different.

             Nevertheless, whatever may be true of other mobile objects, nothing prevents a motion which is not between contraries, such as circular motion, from remaining always the same and continuous and perpetual. This will be more clear from the following. Therefore, although every motion is finite in respect to its termini, nevertheless some motions can be continuous and perpetual through repetition.

             1001. Next where he says, 'As regards the second . . .' (253 a 2), he answers the second argument.

             He says that there is no inconsistency if an inanimate being begins to be moved when before it was not moved, if this happens because an extrinsic mover is sometimes present and sometimes not. For it is clear that motion must pre-exist in the mover which at some time becomes properly a mover when previously it was not. But this seems to be a difficulty which must be investigated: when the mover exists, is the same thing sometimes moved by the same thing and sometimes not? For he said above that this could not occur except through some previous mutation either on the part of the mobile object or on the part of the mover. And thus motion always pre-exists whether the mover pre-exists or not. Hence it seems that this must be asked because he who introduced this argument seems only to inquire why things which are at rest are not always at rest and why mobile objects are not always being moved.

             1002. Next where he says, 'The third objection . . .' (253 a 7), he answers the third argument.

             He says that the third objection especially makes us think that motion can exist when before it was not, as seems to happen in animate things. For it seems that an animal which before was at rest is afterwards moved by a progressive motion, with no motion caused from the exterior. And so it seems that no motion preceded the animal's motion, either in the animal itself or in another, as was said of inanimate things.

             But it is false that the motion of the animal did not come to be from something exterior. For in animals we always see some natural motion, that is, something which is not moved by the will. The cause of this natural motion is not the animal itself through its appetite. Rather the cause of this natural mutation is perhaps the air and ultimately a celestial body, as is clearly apparent when an animal body is altered by the warmth or coldness of the air.

             He says 'perhaps', because in an animal there is also natural motion from an interior principle, as is clear in the mutations in the vegetative soul which are seen in the digestion of food and the subsequent changes. These are called natural because they do not follow apprehension and appetite. But it seems to be contrary to that which is proper to animals for them to move themselves. Therefore, he adds that when we say that an animal moves itself, we do not refer to every motion but to local motion, according to which an animal moves itself through apprehension and appetite.

             Therefore it is possible--in fact it is necessary--that in an animal body there are many changes from the container, that is, the air and a celestial body. Some of these move the intellect or the appetite, and as a further result the whole animal is moved.

             1003. Moreover, it must be noted that he here describes the way in which celestial bodies act on us. They do not act directly on our souls, but on our bodies. When our bodies have been moved, motion occurs per accidens in the powers of the soul which are acts of corporeal organs, but not necessarily in the intellect and in the intellective appetite, which do not use corporeal organs. Sometimes, however, the intellect and the will follow some of the above mutations, as when one through reason chooses either to follow, or reject, or do something because of a passion which has arisen either in the body or in the sensitive part. Therefore he does not say that all motions which are caused by the container move the intellect or the appetite. Rather he says 'some', in order to completely exclude necessity from the intellective part.

             He gives, moreover, examples of the things which he has said. In those who sleep there seems to be the greatest rest in respect to animal motions. Moreover in them there is no sensible motion, that is, no motion which proceeds from sensible apprehension. Again, awakened animals arise because of some motion existing interiorly, either from the work of the nutritive soul, as when the evaporations which cause sleep disappear when food is digested, and the animal is aroused, or because the body is altered by the container through warmth or coldness.

             And so it is apparent to the careful thinker that never does any motion appear anew in us unless it is preceded by some other motion. And he promises that he will make this much clearer in what follows.