Commentary Aristotle Metaphysics
Lecture 13. Change in sensible things not opposed to their truth
But in reply to this theory we shall also say that there is some reason why these men should think that what is changing, when it is changing, does not exist.
Yet there is a problem here, for what is casting off some quality retains something of what is being cast off, and something of what is coming to be must already exist.
And in general if a thing is ceasing to be, there must be something which is; and if a thing is coming to be, there must be something from which it comes to be and something by which it comes to be. This process cannot proceed to infinity.
But setting aside these considerations, let us say that change in quantity and the change in quality are not the same. Let it be granted, then, that a thing does not remain the same in quantity, but it is by reason of its form that we know each thing.
Again, those who hold this view deserve to be criticized, because what they saw in the case of a very small number of sensible things they asserted to be true also of the whole universe. For it is only that region of the sensible world about us which is always in process of generation and corruption. But this is, so to speak, not even a part of the whole, so that it would have been more just for them to have esteemed the changing because of the whole than to misjudge as they did the whole because of its changing part.
Further, it is evident that, in answering these men, we shall say the same things as we said before. For we must show them and make them understand that there is a kind of nature which is immobile.
And those who say that the same thing both is and is not at the same time can also say that all things are at rest rather than in motion. According to this view, there is nothing into which anything may be changed, since everything is already present in everything.
685. He argues against the foregoing opinions.
First, he argues against the views that were held about the changeable character of sensible things;
second, against the statements that were made regarding sensory appearances, at now concerning the truth.
In regard to the first part he gives six arguments.
The first of these is as follows. He who thinks that what is not does not exist has a true opinion and makes a true statement if he expresses this. But what is being changed, while it is being changed, is neither that to which it is being changed nor that from which it is being changed. Thus some true statement can be made about a thing that is undergoing change.
Hence, in opposing the foregoing theory or account (that is, the opinion that no true statement can be made about anything which is changing), we can say that there is some ground or valid reason in their case, according to the opinion of the foregoing philosophers, for thinking that what is changing, or what is being changed, when it is changing, that is, while it is undergoing change, does not exist. In other words, there is some reason why these men should think that it has no being.
686. Yet there is. Then he gives the second argument, and it runs thus. Everything which is being changed already has some part of the terminus to which it is being changed, because what is being changed, while it is being changed, is partly in the terminus to which it is being changed and partly in the terminus from which it is being changed, as is proved in Physics 6 (or, according to another text, that which is casting off some quality retains something of what is being cast off).
And by this statement we are given to understand that anything which is being moved retains some part of the terminus from which it is being moved, because so long as a thing is being moved it is casting off the terminus from which it is being moved, and it is possible to cast off only some quality which belongs to a mobile subject.
And something of what is coming to be must already exist, because everything which is coming to be was coming to be, as is proved in Physics 6.
And it is also evident that, if something is ceasing to be, there must be something which is, for if it did not exist in any way at all, it already would have ceased to be and would not be ceasing to be. Similarly, if something is coming to be, there must be a matter from which it is coming to be and an agent by which it is coming to be. But this cannot go on to infinity, because, as is proved in book 2 (994a11), there cannot be an infinite regress either in the case of material causes or in that of efficient causes.
Hence a major problem faces those who say that no true statement can be made about anything which is being moved or generated, both because each thing which is being moved or generated has some part of the terminus to which it is being moved and because, in every process of generation or motion, there must be held to be something unproduced and unchangeable both on the part of the matter and on that of the agent.
687. But setting aside. Then he gives the third argument, and this rejects the very ground on which these thinkers base their opinion that all sensible things are always in motion.
For they were led to make this statement because of things that increase as a result of growth. For they saw that a thing increases in quantity to a very small degree during one year, and they thought that the motion of growth was continuous, so that quantity, in which increase is observed, might be divided in proportion to the parts of time. Thus an increase in some part of quantity would take place in some part of time, and this part of quantity would be related to a whole quantity as some part of a period of time to the whole of that period. And since this kind of motion is imperceptible, they also thought that things that appear to be at rest are being moved, although by an imperceptible motion.
688. In opposing these thinkers, then, he says that even apart from the considerations which have been made, it is clear that change in quantity and in quality or form are not the same. And although they admit that change in quantity is continuous in reality, and that all things are always being moved imperceptibly by this motion, it is not therefore necessary for this reason that all things should be being moved in quality or form. Hence it will be possible to have a definite knowledge of things, because things are known by their form rather than by their quantity.
689. Again, those who. Then he gives the fourth argument. He says that those who hold this view, that is, those who entertain the opinion that all sensible things are always being moved because they find a small number of sensible things of which this is true, deserve to be criticized. There are many sensible things that are capable of being moved only from the viewpoint of local motion.
For it is obvious that it is only the sensible things around us here in the sphere of active and passive things that are in process of generation and corruption. But this sphere or place amounts to nothing, so to speak, in comparison with the whole universe, for the entire earth has no sensible quantity in comparison with the outermost sphere. Hence this place is related to the universe as its central point, as the astronomers prove on the grounds that the six signs of the zodiac always appear above the earth.
But this would not be the case if the earth were to hide from us some part of the heavens which are perceived by the senses. For it would be foolish to make a judgment about the whole sensible world in the light of these few things. Indeed, it would have been more acceptable if the whole sensible world had been judged according to the motion of the celestial bodies, which far surpass the others in quantity.
690. Further, it is evident. He gives the fifth argument. He says that we must also use the same arguments against these men as were used above in this same book. That is, we must show them that there is a kind of nature which is immobile, namely, that of the primary mover, as is proved in Physics 8. And this argument must be used against them, and they ought to accept it, as has been proved elsewhere. It is not true, then, that all things are always in motion, and that it is impossible to make any true statement about anything.