This, therefore, must be considered assuming another beginning, if any thing moves itself, how, and after what manner it moves. It is necessary then that whatever is moved should be divisible into things. perpetually divisible: for this was before demonstrated in the universal discussions concerning nature, viz. that every thing which is moved essentially is continued. It is impossible, however, that a thing which moves itself, should wholly itself move itself: for the whole would be carried, and would carry according to the same lation, since it is one and an individual in species. It would also be changed in quality, and be the cause of change in quality; so that a man might teach and be at the same time taught, might impart health and be made well, according to the same health. Farther still, it has been shown that a thing which is moveable, is moved; but this while it is moved, is in capacity and not in energy; and that which is in capacity proceeds to energy. But motion is the imperfect entelecheia of that which is moveable; and that which moves is already in energy. Thus, that which is hot, heats; and in short, that which possesses form, generates; so that the same thing will be at once and according to the same hot, and not hot. The like also will take place in every thing else, the mover of which necessarily has the synonymous((Taylor: “Aristotle means such things as move essentially, and is of opinion that in these contradiction is at the same time true if any one says that a thing is moved by itself, and not in things which move and are moved according to accident.”)) Hence, of that which moves itself, one thing moves, and the other is moved. But that it is not possible that the same thing can so move itself, as that each part should be moved by each, is from these arguments evident; for neither will there be any first mover, if each part moves each; since that which is prior is more the cause of a thing being moved, and will more move than that which adheres: for to move is twofold; one kind of mover being that which is moved by something else; and another that which is moved by itself. But that which is more remote from the thing moved is nearer to the principle than that which is between. Again, it is not necessary that the mover should be moved except by itself. According to accident, therefore, the other will reciprocally move. I assume, therefore, that it may happen that it does not move. Hence, one thing will be that which is moved; and another that which moves being immoveable. Farther still, it is not necessary that the mover should be in its turn moved; but either it is necessary that something immoveable should move, or that itself should be moved by itself if it is necessary that motion should always exist. Again, with that motion with which it moves, it will also be moved; so that a thing which heats will be heated. However, neither of that which first moves itself, will one one part, or many parts severally move, themselves: for if the whole should be itself moved by itself, it will either he moved by some one of its parts, or the whole will be moved by the whole. If therefore it is moved, because some one of its parts is moved by itself, this part will be that which first moves itself; for if it were separated, this would itself move itself; but the whole will no longer move itself. But if the whole is moved by the whole, these parts would move themselves accidentally. Hence, if they do not move themselves necessarily, let it be assumed that they are not moved by themselves. Of the whole therefore, one part will move being immoveable; but the other will be moved: for thus alone is it possible that any thing can be self-motive.
Again, if a whole line should move itself, one part of it will move, but the other will be moved. The line A B, therefore, will be rnoved by itself, and by A. But since one thing moves, being moved by something else, but another being immoveable; and since one thing which is moved also moves, but another does not move any thing, it is necessary that a thing which itself moves itself, should consist from that which is immoveable, but moves; and besides this, from that which is moved and does not move from necessity, but just as it may happen: for let A be that which moves indeed, but is immoveable; and let B be that which is moved by A, and moves C. But this is moved indeed by B, but does not move any thing: for though through many media it may some time or other arrive at C, yet let it arrive through one only. The whole, therefore, A B C itself moves itself. But if I should take away C, A B will indeed move itself; for A is that which moves, and B is that which is moved; but C will not itself move itself, nor in short, will it be moved. Nor will the part B C move itself without A: for B moves because it is moved by something else, and not because it is moved by any part of itself. Hence A B will alone itself move itself. It is necessary therefore, that a thing which itself moves itself, should have that which moves being immoveable, and that which is moved, but does not necessarily move any thing. These likewise must either both touch each other, or the one must touch the other. Hence, if that which moves is continued, (for it is necessary that the thing moved should be continued) it is evident that the whole will itself move itself, not because some part of it is such as to move itself; but the whole will itself move itself, and will at the same time move and be moved; because there is some part of it which moves and is moved: for the whole docs not move, neither is the whole moved; but A indeed moves, and B is alone moved. It is however dubious, if any one takes away from A (if that which moves but is immoveable is continued) or from B which is moved; whether the remaining part of A will move, or of B will be moved: for if this be the case, A B will not be that which is first moved by itself; since though something is taken away from A B, nevertheless that which remains of A B will move itself. Or shall we say that nothing prevents both, or one of them, viz. that which is moved, from being divisible in capacity, but indivisible in energy; and that if it were divisible it would no longer possess the same power? Hence, nothing prevents a thing from being primarily inherent in capacity in things divisible. From these things, therefore, it is evident that the nature which primarily moves is immoveable: for whether that which is moved, and is moved by something, immediately stops at the first immoveable, or at that which is itself moved indeed, but moves itself and is permanent; in both ways it will happen that the first mover in all things which are moved, is immoveable.
