Commentary Aristotle Physics
In one sense, it implies a subject, which is either an actual being, as when non-white is in a body, or a potential being, as when privation of substantial form is in prime matter.
In a second sense, “non-being” can imply that no subject is involved; that is, that we are dealing with absolute non-being.
If “non-being” is taken in the first sense—that is, that a subject is implied—then it would be possible to find out how one non-change is contrary to another non-change, for it could be said that a non-change in being is opposed to a non-change in non-being. For since non-being has a subject, there is nothing to prevent that subject from persevering in non-being, which is the same as not changing.
But if there is nothing that is not—that is, if non-being has no subjects—then the question remains: to which non-change is the non-change or rest in being contrary? For what does not exist at all cannot be said to be at rest or to be unchangeably permanent. And, since some kind of non-change must be contrary to non-change or rest in existence, it follows that the non-existence from which generation begins and toward which ceasing to be tends is a non-being that has a subject.
735. Then, at “if it is, then either” (230a12), he explains something he had supposed, namely, that the opposite of generation and of ceasing to be is not rest.
For if it were, then either of two things would follow: first, that not every rest is contrary to motion; or, second, that generation and ceasing to be are motions.
So it is clear that, whatever it is that is opposed to generation and ceasing to be, it is not rest, unless generation and ceasing to be are motion—which they are not, as we have proved above.
736. Then, at “we must say that it is” (230a16), he shows how non-change is contrary to change. And he says that there is a parallel between the contrariety of non-change to change and that of rest to motion: a non-change in being is contrary either to no non-change (which it would be, if non-being has no subject) or to that non-change that is in non-being (if non-being has a subject); and this contrariety is like the opposition between one rest and another.
Or we can say that a non-change in being is the opposite of corruption, as rest is of motion. However, it is not the opposite of generation, because corruption departs from non-change and rest in being, whereas generation tends to it. And we already know that the opposite of motion and change is not rest in the goal, but rest in the starting point.
Lecture 10
Certain difficulties are answered
Again, a further difficulty may be raised. It may be asked how it is that, in local change, both remaining and moving may be natural or unnatural, but in the other changes, this is not so.
For instance, alteration is not now natural and now unnatural, for convalescence is no more natural or unnatural than falling ill, whitening no more natural or unnatural than blackening. So it is also with increase and decrease: these are not contrary to each other in the sense that either of them is natural while the other is unnatural, nor is one increase contrary to another in this sense.
And the same account may be given of generation and corruption: it is not true that generation is natural and corruption unnatural (for growing old is natural), nor do we observe one generation to be natural but another to be unnatural.
We answer that, if what happens under violence is unnatural, then violent corruption is unnatural, and as such, contrary to natural corruption.
Are there then also some generations that are violent and not according to fate (and are therefore contrary to natural generations), and violent increases and decreases—for instance, the rapid growth to maturity of pubescents on account of their food, and the rapid ripening of seeds even when not packed close in the earth? And how is it with alterations?
Surely it is just the same: we may say that some alterations are violent while others are natural—for instance, patients alter naturally or unnaturally according as they throw off fevers on the critical days or not.
But it may be objected that we then shall have corruptions contrary to one another, not to generation. Certainly; and why should not this in a sense be so? Thus, it is so if one corruption is of the sweet and another of the sad, and so one corruption will be contrary to another not simply, but insofar as one has this quality and the other that.
Now, motions and states of rest universally exhibit contrariety in the manner described above: for instance, upward motion and rest above are respectively contrary to downward motion and rest below, these being instances of local contrariety;
and upward locomotion belongs naturally to fire and downward to earth (that is, the locomotions of the two are contrary to each other).
And again, fire moves up naturally and down unnaturally, and its natural motion is certainly contrary to its unnatural motion. So it is also with remaining: remaining above is contrary to motion from above downwards, and to earth this remaining comes unnaturally, but this motion [comes] naturally.
So, the unnatural remaining of a thing is contrary to its natural motion, just as we find a similar contrariety in the motion of the same thing: one of its motions, the upward or the downward, will be natural, the other unnatural.
Here, however, the question arises whether every state of rest that is not permanent has a generation, and whether this generation is a coming to a standstill.
If so, there must be a generation of that which is at rest unnaturally, such as of earth at rest above, and therefore this earth, during the time that it was being carried violently upward, was coming to a standstill.
But, whereas the velocity of that which comes to a standstill seems always to increase, the velocity of that which is carried violently seems always to decrease, and so it will be in a state of rest without having become so.
Moreover, “coming to a standstill” is generally recognized to be identical to, or at least concomitant with, the locomotion of a thing to its proper place.
There is also another difficulty involved in the view that remaining in a particular place is contrary to motion from that place.
For when a thing is moving from or discarding something, it still appears to have that which is being discarded, such that, if a state of rest is itself contrary to the motion from the state of rest to its contrary, the contraries “rest” and “motion” will be simultaneously predicable of the same thing.
But may we not say that, insofar as the thing is still stationary, it is in a state of rest in a certain sense only, not absolutely?
For in fact, whenever a thing is in motion, part of it is where it started, while part is at the goal to which it is changing.
Consequently, a motion finds its true contrary rather in another motion than in a state of rest. With regard to motion and rest, then, we have now explained in what sense each of them is one and under what conditions they exhibit contrariety.
With regard to coming to a standstill, the question may be raised whether there is an opposite state of rest to unnatural as well as to natural motions. It would be absurd if this were not the case, for a thing may remain still merely under violence, and thus we shall have a thing being in a non-permanent state of rest without having become so.
But it is clear that it must be the case, for just as there is unnatural motion, so, too, a thing may be in an unnatural state of rest.
Further, some things have a natural and an unnatural motion: for instance, fire has a natural upward motion and an unnatural downward motion. Is it, then, this unnatural downward motion that is contrary to the natural upward motion, or is it [rather] the natural downward motion of earth [that is contrary]?
It is clear that both are contrary, but not in the same sense: the natural motion of earth is contrary inasmuch as the motion of fire is also natural, whereas the upward motion of fire as being natural is contrary to the downward motion of fire as being unnatural. The same is true of the corresponding cases of rest.
But there would seem to be a sense in which a state of rest and a motion are opposites.
For since it is moved from this and casts it off, it seems still to have what is cast off. So, if the very rest is contrary to that which is thus in opposition to motion, two contraries will exist simultaneously—if it rests a little, or still remains. In general, what is in motion [is opposed] by being here and by what it is being changed into. Therefore, contrary motion is more opposed to motion than rest. Which motion is simply one has been said, and likewise how motion and rest are each one, and what is contrary to what.
737. After discussing the contrariety of motions and of rests, the Philosopher now raises some questions concerning these matters.