LECTURE 9 (256 a 3-257 a 34)

IT IS IMPOSSIBLE FOR A THING TO BE MOVED BY ANOTHER TO INFINITY. IT IS NOT NECESSARY THAT EVERY MOVER BE MOVED

1037. After the Philosopher has shown that whatever is moved is moved by another, he begins here to show that it is necessary to arrive at a first immobile mover.

             This discussion is divided into two parts. First he shows that it is necessary to arrive at some first thing which is either immobile or self-moved. Secondly, where he says, 'Now everything that is . . .' (257 a 35), he shows that even if one arrives at some first thing which moves itself, it is still necessary to arrive further at a first immobile mover.

             Concerning the first part he makes two points. First he shows that it is not possible for a thing to be moved by another to infinity. Secondly, where he says, 'And if we consider . . .' (256 b 3), he shows that it is not necessary that every mover be moved.

             Concerning the first part he makes two points. First he proves his position by ascending in the order of movers and mobile objects, and secondly by descending, where he says, 'This same argument . . .' (256 a 21).

             Concerning the first part he makes two points. First he sets forth certain things which are necessary to prove his position. Secondly, where he says, 'If then everything . . .' (256 a 13), he gives an argument to prove his position.

             1038. He sets forth two things, the first of which is a division of movers.

             Since it was said that whatever is moved is moved by something, a thing can be a mover in two ways. In one way it does not move because of itself, that is, by its proper power, but because it is moved by some other mover, which is a second mover. In another way a thing moves because of itself, that is, by its proper power, and not because it is moved by another.

             Now this latter mover may move in two ways. In one way the first mover moves that which is next after the last, that is, it moves that which is next after the second mover. This happens when the first mover moves a mobile object through only one intermediary. In the other way, the mover moves the mobile through many intermediaries, as is clear when a stick moves a stone and is moved by a hand, which is moved by a man, who does not move because he is moved by another. Therefore, the man is the first mover because of himself, and he moves the stone through several intermediaries. If, however, he were to move the stone by his hand, he would move through only one intermediary.

             1039. Secondly, where he says, 'Now we say . . .' (256 a 9), he compares the first and second movers. When we say that both the first and the last movers move, we say that the first mover moves rather than the last.

             This is clear for two reasons. The first is that the first mover moves the second mover, but not vice versa. The second reason is that the second mover cannot move without the first, but the first can move without the second. For example, a stick cannot move a stone unless it is moved by a man, but a man can move a stone without a stick.

             1040. Next where he says, 'If then everything . . .' (256 a 13), he proves his position from the foregoing. It was shown that whatever is moved is moved by something. That by which it is moved either is moved or not moved. And if it is moved, it is moved either by another or it is not. Moreover, these two, that is, that which is moved by another and that which is not moved by another, are so related that when one has been established, so is the other, but not vice versa. For if there is something which is moved by another, it is necessary to arrive at some first thing which is not moved by another. But if there is some first thing which is not moved by another, it is not necessary for there to be some further thing which is moved by another.

             This, indeed, is clear per se. But there may be some doubt that if something is found to be moved by another, then there should be found some first thing which is not moved by another. Consequently, he proves this as follows.

             If a thing is moved by another, and that again by another, and we never arrive at something which is not moved by another, it follows that we proceed to infinity with respect to movers and things moved. That this is impossible was proven above in Book VII. But here he proves this in a more certain way, because among infinite things there is no first. Therefore, if movers and the things which are moved proceed to infinity, there will be no first mover. But it was already said that if the first mover does not move, then neither does the last mover move. Therefore, there will not be any mover, which is clearly false. Hence a thing is not moved by another to infinity.

             Let it be granted that whatever is moved is moved by something, as was shown, and further, let it be assumed that the first mover is moved. Since it has been proven that it is not moved by another, it must be moved by itself.

             However, it should be noted that in this argument it is not proven that the first mover is moved. Rather he assumes this according to the common opinion of the Platonists. With respect to the force of the argument it is not to be concluded that the first mover moves itself rather than that it is immobile. Hence in what follows he draws this same conclusion in a disjunction, as will be clear below.

             1041. Next where he says, 'This same argument . . .' (256 a 21), he proves the same thing by descending. This argument is the same as the foregoing with respect to the force of the inference, differing only in the order of procedure. He repeats it for greater clarity.

             He says, therefore, that the previous argument can be developed in another way. He sets forth propositions which have the same nature [ratio] of truth as the foregoing, but in another order. He said above that whatever is moved is moved by another, and that that by which it is moved moves either because of itself or because of a prior mover. This is the procedure of ascending.

             Here, however, he proceeds conversely by descending. He says that every mover moves something and moves by something, either by itself or by another lower mover. For example, a man moves a stone either by himself or by a stick, and the wind hurls something to the ground either by its own power or by a stone which it moves.

             He has also stated above that the last mover does not move without the first, but the opposite may occur. In place of this he says here that it is impossible for that which moves as an instrument to move something without a principal mover. For example, a stick cannot move without a hand. But if a thing moves by itself as a principal mover, it is not necessary for there to be an instrument by which it moves. This is clearer in instruments than in ordered mobile objects, even though it is the same truth. For no one would doubt that the second mover is the instrument of the first. Just as he said above that if something is moved by another there must be something which is not moved, but not vice versa, so here he says by descending that if there is an instrument by which a mover moves there must be something which moves, not by an instrument, but by itself, or else there is an infinite series of instruments. This is the same as an infinite series of movers, which is impossible, as was shown above.

             If, therefore, there is something which moves that which is moved, it is necessary to stop and not proceed to infinity. For if a stick moves because it is moved by a hand, it follows that the hand moves the stick. If, however, something else also moves the hand, it also follows conversely that some mover moves the hand. And so what follows for moved instruments must also follow for the movers which move the instruments. But it was proven above that there is no infinite series of movers. Therefore neither is there an infinite series of instruments. Therefore, since a thing which is moved is always moved by another, and since there is no infinite series, there must be some first mover which moves through itself and not through an instrument.

             If, therefore, it is granted that this first thing which moves through itself is moved, but there is no other thing moving it (for thus it would be the instrument), it follows necessarily that it moves itself, supposing, according to the Platonists, that every mover is moved.

             And so, also according to this argument, that which is moved will either be moved immediately by a thing which moves itself, or else one will at some time arrive at a mover which moves itself.

             1042. Next where he says, 'And if we consider . . .' (256 b 3), he shows that not every mover is moved, which was assumed in the above arguments.

             Concerning this he makes two points. First he proves that not every mover is moved. Secondly, where he says, 'It is not necessary . . .' (257 a 25), he concludes to his main point from both this and the above arguments.

             He says, therefore, first that the following points can be added to the above to prove our position. Concerning this he makes three points. First he sets forth a certain division. Secondly, where he says, 'Let us consider . . .' (256 b 8), he rejects one alternative. Thirdly, where he says, 'We will now take . . .' (256 b 27), he rejects the other alternative.

             He says, therefore, first that if everything which is moved is moved by something which is moved, that is, if every mover is moved, this can be taken in two ways. This might be found in things per accidens such that the mover does not move because of that which is moved (for example, we might say that a musician is a builder, not because he is musical, but per accidens). Or the mover might be moved per se and not per accidens.

             1043. Next where he says, 'Let us consider . . .' (256 b 8), he rejects the first alternative in three ways.

             First he uses the following argument. Nothing which is per accidens is necessary. For what is in a thing per accidens is not in it of necessity, but might happen to be not in it, as music in the builder. If, then, movers are moved per accidens, it follows that they might not be moved. But when you grant that every mover is moved, then it follows that if movers are not moved, they do not move. It follows, then, that at some time nothing would be moved. This is impossible, however, since it was shown above that motion must be eternal. This impossibility, however, does not follow because we have assumed that movers are not moved. For if it is per accidens that movers are moved, then it will be possible for movers not to be moved. For no impossibility follows from an assumed possibility. The conclusion, therefore, from this is that it is impossible that every mover be moved.

             1044. Secondly where he says, 'Moreover, the conclusion . . .' (256 b 14), he proves the same thing with another probable argument, which is as follows.

             Three things are found in motion: one is the mobile object which is moved; another is the mover; and the third is the instrument by which the mover moves. Of these three it is clear that that which is moved must be moved, but it is not necessary that it move. The instrument by which the mover moves must both move and be moved (for it is moved by the principal mover, and it moves the ultimate thing moved). Hence everything which both moves and is moved has the nature [ratio] of an instrument.

             Therefore, the instrument by which the mover moves both moves and is moved, because it communicates with both, having a certain identity with that which is moved. This is particularly clear in local motion. For from the first mover up to the ultimate thing moved, everything must be in contact with everything else. And so it is clear that the intermediate instrument is the same through contact with the mobile object, and thus is moved together with it insofar as it communicates with it. But it also communicates with the mover. For it is a mover, in the sense that it is an instrument by which it moves. But it is not immobile.

             Therefore, from the foregoing it is clear that the ultimate thing moved is indeed moved, but it does not have within itself a principle of moving either itself or another. It is moved by another, not by itself. Hence it seems to be reasonable, that is, probable (we do not care to say at the present time that it is necessary) that there is some third thing which moves, though it is immobile.

             For it is probable that if two things are joined per accidens, and if one is found without the other, then that other will also be found without the first. (It is necessary that it can be found without the other, because things which are joined per accidens can be not joined.) For example, if whiteness and sweetness are joined per accidens in sugar, and if whiteness is found without sweetness, as in snow, it is probable that sweetness will be found in something without whiteness, as in cinnamon. Therefore, if a mover is moved per accidens, and if 'being moved' is found in something without a 'moving', as in the ultimate thing moved, then it is probable that a 'moving' will be found without a 'being moved', such that there may be some mover which is not moved.

             It is clear from this that such an argument has no force in regard to substance and accident, and matter and form, and in similar things, of which one is found without the other, but not vice versa. For accident is in substance per se, and it is per se agreeable to matter to have existence through form.

             1045. Thirdly, where he says, 'So, too, Anaxagoras . . .' (256 b 25), he proves the same thing from the testimony of Anaxagoras.

             For since there is a mover which is not moved, Anaxagoras spoke correctly when he said that intellect is impassive and unmixed. He said this because he held that intellect is the first principle of motion. For only if it is unmixed will it be able to move and command without being moved. For that which is mixed with another is moved in some way when the other is moved.

             1046. Next where he says, 'We will now take . . .' (256 b 27), he takes up the other part of the division, that is, whatever is moved is moved by something which is moved per se and not per accidens.

             He rejects this with two arguments, the first of which is as follows. If the mover is moved, not accidentally, but necessarily, and if it can never move without being moved, this must occur in two ways. One way is that the mover is moved with respect to the same species of motion by which it moves. The other way is that the mover is moved according to one species of motion, and that which is moved is moved according to another species of motion.

             He next explains the first way where he says, '. . . either that which is . . .' (256 b 31). We say that the mover is moved with respect to the same species of motion when, for example, that which heats becomes hot, and when that which cures is cured, and when that which moves in place is moved in place.

             He explains the second way where he says, '. . . or else that which is making healthy . . .' (256 b 33). This means that a thing moves and is moved according to different species of motion.

             Next he shows the impossibility of the first way where he says, 'But it is evident . . .' (256 b 34).

             It is clearly impossible for a mover to be moved with respect to the same species of motion. For it is not sufficient to stop at some subalternate species, but one must proceed by division all the way to the most specific species. For example, if someone teaches, not only is he taught, but he teaches and is taught the same thing. If he is teaching geometry, he is taught this same geometry. Or if he moves according to the species of local motion which is called throwing, then he is moved according to the same motion of throwing. And this is clearly false.

             Next he rejects the second mode, that is, the mover is not moved according to the same species of motion, but rather it moves by one genus of motion, and is moved by another genus. For example, the mover moves with respect to place and is moved by increase, or else the mover moves by increase and is moved by another through alteration. And that which alters it is moved by some other motion.

             It is clear that motions are not infinite, either in genus or in species. For it was shown in Book V that motions differ in genus and in species with respect to the differences of the things in which there are motions. Moreover, the genera and species of things are not infinite, as he has proven elsewhere. And so, neither are the genera and species of motion infinite. If, then, the mover must be moved by another genus or another species of motion, this will not go on to infinity. Rather there will be some first immobile mover.

             1047. But someone might say that when all the species of motion are exhausted, there will be a return to the first, that is, if the first thing moved is moved locally, then when all the genera and species of motions have been distributed through different movers, the mover which remains will be moved by local motion. To reject this he says next that if there is this cycle such that that which alters is moved in place (he says this because above he named local motion first and alteration last), then this cycle is the same as if it were said immediately at the beginning that the mover is moved in place, and not only in genus but also in species, as when he said that the teacher is taught.

             And that this is so he proves as follows. Whatever is moved is moved more by a higher mover than by a lower one, and consequently much more by the first mover. Therefore, if that which was given as moved locally is moved by the nearest mover which is increased, and that again is moved by something which is altered, and that again is moved by something which is moved in place, then that which is moved with respect to place will be moved more by the first thing which is moved with respect to place than by the second thing which is altered or by the third thing which is increased.

             Therefore, it will be true to say that that which moves with respect to place is moved with respect to place. And the same can be said of each species of motion. However, this is not only erroneous, as can be seen in many instances, but it is also impossible. For it would follow that the teacher is learning while he teaches, which is impossible. This is a contradiction, because a teacher has a science but a learner does not. Hence it is clear that a mover is not necessarily moved.

             1048. He gives the second argument where he says, 'Still more unreasonable . . .' (257 a 14). This argument differs from the preceding one only in that the first argument led to certain particular inconsistencies, for example, that the thrower is thrown, or that the teacher is taught. This argument, however, leads to a general inconsistency.

             He says that although it is inconsistent that the teacher is taught, the following is even more unreasonable. For if nothing is moved except by that which is moved, then every motive force is mobile. And thus it will follow that every mover is mobile. For example, it might be said that whatever has the power of curing, or which is actually curing, is curable; and whatever has the power of building is buildable. This is more unreasonable than saying that a teacher is taught, for the teacher was first capable of learning, but the builder was never built.

             This follows in two ways. For if it is granted that every mover is moved according to the same species of motion, then it follows immediately that the builder is built, and that the one who cures is cured. And if it is granted that the mover is not moved according to the same species of motion, it follows that it comes to the same thing through many intermediaries.

             And he explains this. Let it be granted that every mover is moved by another, although it is not moved immediately by the same motion by which it moves, but by another motion. For example, that which has the power to cure is not immediately cured but is moved by the motion of learning. Nevertheless, since the species of motion are not infinite, by ascending from mobile object to mover we will arrive at some time at the same species of motion, as was explained above.

             One of these two is clearly impossible, that is, that the builder is immediately built. And the other, that is, that it comes to this through many intermediaries, seems to be a fiction. For it is inconsistent to say that that which naturally alters necessarily is naturally increased.

             1049. Therefore, from an examination of the foregoing arguments (the first of which concluded that whatever is moved is not moved by another to infinity, and the second of which concluded that not every mover is moved), from all of these arguments we can conclude that it is not necessary that that which is moved be moved by another to infinity such that it is always moved by a mover which is moved. Therefore, it is necessary to stop at some first. This first must be either immobile or a mover of itself.

             But if it is asked whether the first cause of motion in the genus of mobile objects is that which moves itself or a mobile object which is moved by another, it is probable among all that the first mover is that which moves itself. For a cause per se is always prior to a cause through another. And it is for this reason that the Platonists held that before things which are moved by another there is something which moves itself.

             Therefore, we must consider that which moves itself and make another beginning, that is, we must consider that if something moves itself, how is this possible.