Commentary Aristotle Physics
Lecture 2
Which species of change is motion in the strict sense
And, since every change is from something to something—as the word itself (metabole) indicates, implying something “after” (meta) something else, something earlier and something later—that which changes must change in one of four ways: from subject to subject, from subject to non-subject, from non-subject to subject, or from non-subject to non-subject, where by “subject” I mean what is affirmatively expressed.
So, it follows necessarily from what has been said above that there are only three kinds of change: from subject to subject, from subject to non-subject, and from non-subject to subject.
For the fourth conceivable kind, that from non-subject to non-subject, is not change, as there is in that case no opposition either of contraries or of contradictories.
Now, change from non-subject to subject, the relation being that of contradiction, is “generation”—“unqualified generation” when in an unqualified way, and “particular generation” when in a particular character.
For instance, a change from not-white to white is a generation of the whole thing, white, while change from unqualified non-being to being is generation simply, in respect of which we say that a thing comes to be without qualification, not that it comes to be some particular thing.
Change from subject to non-subject is “corruption”—“unqualified corruption” when the change is from being to non-being, and “particular corruption” when the change is to the opposite negation, the distinction being the same as that made in the case of generation.
Now, the expression “non-being” is used in several senses, and there can be motion neither of that which “is not” in respect of the affirmation or negation of a predicate, nor of that which “is not” in the sense that it only potentially “is,” that is to say, the opposite of that which actually “is” in an unqualified sense.
For although that which is “not-white” or “not-good” may nevertheless be in motion accidentally (for example, that which is “not-white” might be a man), yet that which is without qualification “not-so-and-so” cannot in any sense be in motion, and therefore, it is impossible for that which is not to be in motion.
This being so, it follows that “generation” cannot be a motion, since it is that which “is not” that “becomes.” For however true it may be that it accidentally “becomes,” it is nevertheless correct to say that it is that which “is not” that in an unqualified sense “becomes.” And it is similarly impossible for that which “is not” to be at rest.
There are these difficulties, then, in the way of the assumption that what “is not” can be in motion;
and it may be further objected that, whereas everything that is in motion is in space, that which “is not” is not in space, for then it would be somewhere.
So, too, “corruption” is not a motion, because a motion has for its contrary either another motion or rest, whereas “corruption” is the contrary of “generation.”
Since, then, every motion is a kind of change and there are only the three kinds of change mentioned above, and since, of these three, those that take the form of “generation” and “corruption”—that is to say, those that imply a relation of contradiction—are not motions, it necessarily follows that only change from subject to subject is motion.
And every such subject is either a contrary or an intermediate (for a privation may be allowed to rank as a contrary) and can be affirmatively expressed, such as naked, toothless, or black.
649. After distinguishing per se from per accidens motion, the Philosopher now divides per se change and motion into its species.
Here, it should be noted that, when Aristotle defined motion in book 3, he took it as being common to all species of change. It is in this sense that he now uses the word “change.” And he is beginning to use the word “motion” in a stricter sense, that is, for a certain species of change.
Therefore, this section is divided into two parts:
in the first, he divides change into its various species, of which one is motion;
in the second, he subdivides motion into its species, at “if, then, the categories” (225b5; [660]).
About the first, he does two things:
first, he gives his division of change;
second, he explains the parts of the division, at “now, change from non-subject” (225a12; [653]).
About the first, he does three things:
first, he states certain things that must be mentioned before dividing change;
second, from these, he infers the division of change, at “so, it follows necessarily” (225a7; [651]);
third, he answers an objection, at “for the fourth” (225a10; [652]).
650. He first says (224b35) that, since every change is from something to something—as is clear from the very word “change,” which denotes that something is after something else, that is, something earlier and something later—it follows from all this that what changes must change in one of four ways.
For both termini might be affirmed, in which case something is said to be changed from subject to subject;
or the terminus from which is affirmed and the terminus to which negated, in which case something is changed from subject to non-subject;
or on the other hand, the terminus from which is negated and the terminus to which affirmed, in which case something is moved from non-subject to subject.
Finally, both termini might be negated, in which case something is said to be changed from non-subject to non-subject. Here, the word “subject” is not taken in the sense of that which sustains a form; rather, anything that is affirmatively expressed is here called a “subject.”
651. Then, at “so, it follows necessarily” (225a7), he derives from these premises his division of change.
And he says that it necessarily follows from these premises that there are three kinds of change:
one is from subject to subject, as when something is changed from white to black;
another is from subject to non-subject, as when something is changed from being to non-being;
the third is from non-subject to subject, as when something is changed from non-being to being.
652. Then, at “for the fourth” (225a10), he precludes a possible objection. For someone might object that, since he mentioned four ways in which change can take place, he should have derived four kinds of change and not merely three. But he dismisses this objection by saying that there cannot be any kind of change from non-subject to non-subject, because every change takes place between opposites and two negations are not opposites. For they are neither contrary nor contradictory. A further proof of this is that any pair of negatives may chance to be true of one and the same thing at the same time; for example, a stone is neither healthy nor sick. Hence, since per se change occurs only between contraries and contradictories, as was pointed out above, it follows that there is no per se change from one negation to another. Such changes would always be per accidens, for when something changes from white to black, it at the same time also changes per accidens from non-black to non-white. This is the way that something is changed from non-subject to non-subject. However, what is per accidens in any genus cannot be a species of that genus. Therefore, there can be no species of change from non-subject to non-subject.
653. Then, at “now, change from non-subject” (225a12), he explains the parts used in his division.
About this, he does three things:
first, he explains the first two parts;
second, he shows that neither of them is motion, at “now, the expression” (225a20; [656]);
third, he concludes that the remaining part is motion, at “since, then, every motion” (225a34; [659]).
About the first, he does two things.
First, he explains one part of the division;
second, he explains a second part, at “change from subject” (225a17; [655]).
654. He says first (225a12) that the change from non-subject to subject takes place between contradictories and is called generation, which is the change from non-being to being.
Now, this can take place in two ways:
one is unqualified generation, by which something comes to be in the strict sense of the word;
the other is a particular kind of coming to be, that is, in a qualified way.
And he gives an example of both kinds.
First of all, of the second kind, he says that, when something is changed from non-white to white, it is not an unqualified coming to be of the whole thing, but a mere coming to be of its whiteness.
Then he gives an example of the first, and he says that generation from non-being to being in the order of substance is generation simply, in regard to which we say that a thing comes to be without qualification. And, since generation is a change from non-being to being, a thing is said to be generated when it is changed from non-being to being.
However, when something passes from non-white to white, it is not being changed from absolute non-being to absolute being. For speaking strictly, what is being changed is the subject, and the subject of white is an actually existing being.
Hence, since the subject remains throughout the whole change, there already was an actually existing being at the beginning of the change, simply speaking; but it was not a being actually existing as white. Consequently, it was not a case of unqualified coming to be, but a coming to be this, namely white.
But the subject of substantial form is not an actual being, but rather a merely potential one, namely, prime matter, which is under privation at the beginning of generation and under form at the end.
And, so, in the case of a substance being generated, it is said that something comes to be in an unqualified sense.
From this, it can be concluded that, when it is a case of the coming to be of a form that presupposes another form remaining in the matter, it is not unqualified generation, but generation in a particular way, because each form makes a being actual.
655. Then, at “change from subject” (225a17), he makes clear the other part of the division and states that that change which is from subject to non-subject is called corruption, but there is an unqualified corruption, from substantial being to non-being, and another certain corruption that is into the opposite negation of any affirmation, as from white to non-white, which is particular corruption, as has already been said of generation.
656. Then, at “now, the expression” (225a20), he shows that neither of these cases is motion:
first, that generation is not motion;
second, that corruption is not motion, at so, too, “corruption” (225a32; [658]).
He proves the first by two arguments.
In the first argument, he says that what is not unqualifiedly a “this something” cannot be moved, because what does not exist is not moved; but what is unqualifiedly generated is not a “this something,” for it is strictly speaking a non-being. Therefore, what is unqualifiedly generated is not being moved. Hence, unqualified generation is not motion.
In explanation of the first premise, he says that non-being is spoken of in three senses: in the first two senses, non-being is not subject to motion, but in the third, it is subject to per accidens motion.
In one sense, being and non-being refer to the affirmation and negation of a predicate in a proposition, where they refer to truth and falsity; in this sense, being and non-being exist only in the mind, as is said in Metaphysics 6. Hence, they are not subject to motion.
In another sense, what is in potency is called non-being insofar as being in potency is the opposite of unqualified being in act. Taken in this sense, no motion is possible.
In a third sense, that is called “non-being” that is in potency in such a way as to exclude not unqualified actual existence, but actually being such-and-such, such as when non-white is called non-being and non-good. Such non-being is subject to motion per accidens, inasmuch as such non-being is attached to an actually existing thing subject to motion (as when a man is said to be non-white).
Now, why is it that what is not unqualifiedly a “this something” is not subject to motion at all, neither per se nor per accidens? It is because it is impossible for the non-existent to be moved. Consequently, it is impossible for generation to be a motion, since generation concerns itself with what is not.
And, although it was said in book 1 that something comes to be per accidens from non-being and per se from a being in potency, yet it is true to say of what is absolutely coming to be that, strictly speaking, it is non-being; hence, such a thing cannot be moved, and for the same reasons, cannot be at rest. Hence, generation is neither motion nor rest. But, if anyone insists that generation is motion, he will be forced to admit the strange proposition that non-being can be moved and can be at rest.
657. He gives a second reason at “and it may be further” (225a31), which is this. Whatever is moved is in a place; but what does not exist is not in a place, or otherwise its place could be pointed out. Therefore, what does not exist is not moved.
The truth of the first statement is evident from the fact that, since local motion is the first of all motions, whatever is moved has to be moved in respect of place and, consequently, must be in a place. But, if you remove what is prior, you remove whatever depends upon it.
658. Then, at so, too, “corruption” (225a32), he proves that ceasing to be is not a motion, because nothing is contrary to a motion but motion and rest, whereas the contrary of ceasing to be is generation, which is neither motion nor rest, as we have shown. Therefore, ceasing to be is not a motion.
659. Then, at “since, then, every motion” (225a34), he concludes that the remaining member of the above-given division is motion: since motion is a definite kind of change, because there is in it something following something (which pertains to the very idea of motion), and so motion is neither generation nor ceasing to be (which are changes between contradictories), it follows of necessity that motion is from subject to subject, since there are only three species of change. By two subjects is understood two that are affirmative, whether they be contraries or intermediates, for even privation is a kind of contrary that is expressed affirmatively, such as nude, which is a privation, and such as white and black, which are contraries.