LECTURE 7 (254 b 7-255 a 18)

WHATEVER IS MOVED IS MOVED BY ANOTHER

1021. After the Philosopher has explained his intention, he here begins to develop it; namely, not everything is sometimes moved and sometimes at rest. Rather there is something which is absolutely immobile, and something which is always moved.

             This discussion is divided into two parts. First he shows that the first mover is immobile. Secondly, where he says, 'And further, if there is . . .' (259 b 32), he shows that the first mobile object is always moved.

             The first part is divided into two parts. First he shows from the order of movers and mobile objects that the first mover is immobile. Secondly, where he says, '. . . but also by considering . . .' (259 a 21), he proves the same thing from the eternity of motion.

             The first part is divided into two parts. First he shows that the first mover is immobile. Secondly, where he says, 'Since there must always . . .' (258 b 10), he shows that the first mover is eternal.

             Concerning the first part he makes two points. First he explains something that is necessary for the proof of what follows; namely, whatever is moved is moved by another. Secondly, where he says, 'Now this may come about . . .' (256 a 3), he proves his position.

             He has shown above at the beginning of Book VII that whatever is moved is moved by another with a common argument taken from motion itself. But since he has begun to apply motion to mobile things, he shows that that which was proven universally above is universally verified in all movers and mobile objects.

             Hence the first part is divided into two parts. First he gives a division of movers and mobile objects. Secondly, where he says, 'The fact that a thing . . .' (254 b 24), he explains the proposition in individual cases.

             Concerning the first part he makes two points. First he divides movers and mobile objects. Secondly, where he says, 'Thus in things that . . .' (254 b 15), he explains this division.

             1022. First, therefore, he gives three divisions of movers and mobile objects.

             The first of these is that some movers and mobile objects move or are moved per accidens, and some per se. Here he uses 'per accidens' in the broad sense, according to which it includes even that which is 'according to a part'. Hence, to explain the meaning of 'per accidens', he adds that a thing can be said to move or be moved per accidens in two ways. First, those things are said to move per accidens which are said to move because they are in certain movers. For example, it is said that music cures, because he who cures is musical. Similarly, those things are said to be moved per accidens which are in things which are moved, either as located in a place, as when we say that a man is moved because he is in a ship which is moved, or else as an accident in a subject, as when we say that white is moved because a body is moved. Things are said to move or be moved per accidens in another way insofar as they move or are moved according to a part. For example, a man is said to strike or be struck because his hand strikes or is struck. Those things are said to be moved or to move per se which are free of the two preceding modes. For they are not said to move or be moved because they are in other things which move or are moved, nor because some part of them moves or is moved.

             Omitting things which move or are moved per accidens, he subdivides those which are moved per se. First, of those things which are moved per se some are moved by themselves, such as animals, and others are moved by others, such as inanimate things.

             He gives a third division; namely, some things are moved according to nature, and others are moved outside of nature.

             1023. Next where he says, 'Thus in things that . . .' (254 b 15), he explains how motion according to nature and motion outside of nature is found in things which are moved by themselves and in things which are moved by another.

             He says first that things which are moved by themselves (as are animals, which move themselves) are moved according to nature. He proves this from the fact that they are moved by an intrinsic principle. We say that those things whose principle of motion is in themselves are moved by nature. Hence it is clear that the motion of an animal by which it moves itself, if compared to the whole animal, is natural, because it is from the soul, which is the nature and form of the animal. But if it is compared to the body, it happens that motion of this kind is both natural and outside of nature. For this must be considered according to the diversity of motions and of elements from which the animal is constituted. If an animal is composed of predominantly heavy elements, as is the human body, and if it is moved upward, then this motion will be violent in respect to the body. But if it is moved downward, this motion will be natural to the body. If, however, there are some animal bodies which are composed of air, as some Platonists held, then the contrary must be said of them.

             Secondly, he explains how violent and natural motion are found in things which are moved by another.

             He says that some of these are moved according to nature; for example, fire is moved upward and earth downward. But some are moved outside of nature; for example, earth upward and fire downward. This latter is violent motion.

             Thirdly, he gives another mode of unnatural motion in animals according to which the parts of animals are often moved outside of nature if one considers the natures [ratio] and modes of natural motion in the parts of animals. For example, a man bends his arms forward and his legs backward; but dogs and horses and such animals bend their front feet to the rear and their rear feet to the front. But if a contrary motion occurs in animals, the motion will be violent and outside of nature.

             1024. Next where he says, 'The fact that a thing . . .' (254 b 24), he proves that whatever is moved is moved by another.

             He shows this first in cases in which it is obvious. Secondly, where he says, 'The greatest difficulty . . .' (254 b 33), he shows this in cases in which it is open to question.

             He omits, however, things which are moved per accidens, because such things are not themselves moved, but are said to be moved because some other things are moved. Among things which are moved per se, it is especially clear that things which are moved violently and outside of nature are moved by another.

             For it is clear from the very definition of violence that things which are moved by violence are moved by another. For as is said in Ethics, III, the violent is that whose principle is outside, the patient contributing none of the force.

             After he has shown that things which are moved by violence are moved by another, he shows that things which are naturally moved by themselves, as animals are said to move themselves, are also moved by another. For in these cases it is clear that something is moved by another. But there can be a difficulty of how one should designate the mover and the moved in these cases. At first sight it seems (and many think this) that that which moves and that which is moved are distinct in animals, just as they are in ships and in other artificial things which do not exist according to nature. For it seems that the soul which moves is related to the body which is moved as a sailor is related to a ship, as is said in De Anima, II. Thus it seems that a whole animal moves itself insofar as one part of it moves another. Whether the soul is related to the body as a sailor to a ship he leaves for investigation in De Anima. He will explain later how a thing is said to move itself insofar as one part of it moves and another part is moved.

             1025. Next where he says, 'The greatest difficulty . . .' (254 b 33), he explains his position in cases in which there is greater difficulty.

             Concerning this he makes three points. First in regard to cases in which there is greater difficulty he states that whatever is moved is moved by another. He is referring to heavy and light things when they are moved according to nature. Secondly, where he says, 'It is impossible . . .' (255 a 5), he shows that such things do not move themselves. Thirdly, where he says, 'It is the fact that . . .' (255 a 19), he explains how they are moved.

             He says, therefore, first that it is rather clear that the proposition 'whatever is moved is moved by another' applies to things which are moved by violence and to things which move themselves. The main difficulty arises in the remaining alternative of the last division, namely, in things which do not move themselves, but are nevertheless moved naturally.

             He says the 'last' division; namely, of things which are not moved by themselves but by another, some are moved outside of nature and some on the contrary are moved according to nature. In the latter cases the difficulty is: by what are they moved? For example, heavy and light things are moved to their contrary places by violence and to their proper places by nature, that is, the light is moved upward and the heavy downward. But what moves them is not clear when they are moved by nature as it is when they are moved outside of nature.

             1026. Next where he says, 'It is impossible . . .' (255 a 5), he proves with four arguments that such things do not move themselves.

             The first of these is that to move oneself pertains to the nature [ratio] of life and is proper to living things. For by motion and sensation we distinguish the animate from the inanimate, as is said in De Anima, I. Now it is clear that these things are not living or animated. Therefore they do not move themselves.

             1027. He gives the second argument where he says, 'Further, if it were . . .' (255 a 7). The argument is as follows.

             Things which move themselves can also be the cause of their own rest. For example, we see that by their appetites animals are moved and stopped. Therefore, if heavy and light things move themselves by natural motion, they would be able to stop themselves, just as if a man is the cause of his own walking, he is also the cause of his non-walking. But we see that this is false, because such things are not at rest outside of their proper places unless some extrinsic cause prevents their motion. Therefore they do not move themselves.

             But someone might say that even though such things are not the cause of their own rest outside of their proper places, nevertheless, they are the cause of their own rest in their proper places. Hence he adds a third argument where he says, '. . . and so, since on this supposition . . .' (255 a 9). The argument is as follows.

             It is irrational to say that things which move themselves are moved by themselves with respect to only one motion and not a plurality of motions. For that which moves itself does not have its motion determined by another, but determines its own motion. Sometimes it determines for itself this motion, and sometimes another. Hence, that which moves itself has the power to determine for itself either this or that motion. Therefore, if heavy and light things move themselves, it follows that if fire has the power to be moved upward, it also has the power to be moved downward. But we never see this happen except through an extrinsic cause. Therefore they do not move themselves.

             It should be noted, however, that these two arguments are probable with respect to those things which are apparent in things which move themselves among us. Such things are found to be moved sometimes by this motion, sometimes by another motion, and are sometimes at rest. And so he did not say 'impossible' but 'irrational', which is his custom when speaking of probables. For he will show below that if there is some self-motion in which the mover is altogether immobile, then it is moved always and by one motion. But this cannot be said of heavy and light things in which there is not something which is not moved per se or per accidens, since they are generated and corrupted.

             1028. He gives the fourth argument where he says, 'Again, how can anything . . .' (255 a 12). The argument is as follows.

             No continuous thing moves itself. But heavy and light things are continuous. Therefore, none of these moves itself.

             He proves as follows that no continuous thing moves itself. The mover is related to the moved as agent to patient. When, however, the agent is contrary to the patient, a distinction is necessary between that which naturally acts and that which is naturally acted upon. Therefore, insofar as some things are not in contact with each other, but are altogether one and continuous both in quantity and form, they cannot be acted upon by each other. Therefore, it follows that no continuous thing moves itself. Rather the mover is separated from that which is moved, as is clear when inanimate things are moved by animate things, as a stone by a hand. Hence in animals which move themselves there is a certain collection of parts rather than a perfect continuity. For one part can be moved by another, but this is not found in heavy and light things.