Metaphysics

​Since there were three substances, two physical and one immovable, about this latter we must say that it is necessary that there should be some eternal immovable substance. For substances are the first of existing things, and if they are all destructible, all things are destructible; but it is impossible that movement should either come into being or be destroyed (for it always was), nor yet time. For it is not possible that there should be “before” and “after” if time is not; and movement also, then, is continuous in the same way as time; for time is either the same as movement or some affection of movement. But there is no continuous movement except movement in place, and of this only circular movement. But indeed, if there is something capable of moving or of acting, but not active, there will be no movement; for that which has power may not act. There is no use, then, even if we make eternal substances, as do those who assume the Ideas, unless there is in them some principle capable of causing change; nor, indeed, will this be sufficient, nor another substance besides the Ideas; for if it does not act, there will be no movement. Further, not even if it acts, but its substance is potentiality; for then there will be no eternal movement; for that which is in potentiality may fail to be. There must then be such a principle whose substance is actuality. Further, then, these substances must be without matter; for they must be eternal, if indeed anything else is eternal. They must, then, be actuality. Yet there is a difficulty; for it seems that everything active is capable of acting, but not everything capable of acting is active, so that potentiality is prior. But indeed, if this is so, nothing of existing things will be; for it is possible for things to be capable of being and yet not to be. And yet, if it is as the theologians say who generate all things from Night, or as the physicists say who say “all things were together”, the same impossibility occurs. For how will they be moved, if there is to be no cause in actuality? For matter will not move itself, but the craft of carpentry will; nor will the menses or the earth move themselves, but the seeds and the semen. Therefore some assume an eternal actuality, as do Leucippus and Plato; for they say that there is always movement. But why and what it is they do not say, nor, if it is in this way or that, do they state the cause. For nothing is moved by chance, but there must always be some cause present, just as now it is moved in this way by nature, and in that way by force or by intellect or by something else. (Then, which is first? For this makes an immense difference). But indeed, neither is it possible for Plato to state what he sometimes thinks is the principle, namely, that which moves itself; for the soul is subsequent to and contemporary with the heaven, as he says. Now, to think that potentiality is prior to actuality is in one sense right and in another not (and how this is has been said); but that actuality is prior Anaxagoras witnesses (for intellect is actuality) and Empedocles with Love and Strife, and those who say that movement is eternal, such as Leucippus; so that there was no Chaos or Night for an infinite time, but the same things always existed, either in a cycle or otherwise, if indeed actuality is prior to potentiality. If, then, the same thing is always in a cycle, there must be something that always remains acting in the same way. And if there is to be generation and destruction, there must be something else which is always acting in different ways. It must, then, act in this way by itself, and in that way by another; and either, then, by that other or by the first. It must, indeed, be by the first; for that is again the cause of itself and of the other. Therefore the first is better; for that was the cause of the “always in the same way”, and the other of the “otherwise”, and both of the “always otherwise” obviously. Therefore the movements also are in this way. Why then should we seek other principles?