Commentary Aristotle Physics
And the answer seems to be “no,” for two reasons.
First of all, if there is coming to be of every state of rest that is not eternal, it will follow that there is coming to be for states of rest that are outside nature (as when earth is at rest above). Now, rest can be produced only by a previous motion, and the motion preceding an unnatural state of rest is by force. Consequently, it follows that, when earth is violently projected upward, it is then that it comes to a standstill, that is, that rest then comes to be. But this cannot be, because the velocity of that which comes to a standstill seems always to increase; that is, when rest is being generated through motion, it is true that, as the state of rest gets closer, the motion gets swifter. For since the perfection of coming to be is the thing produced, and since each thing gets stronger and more intense as it gets closer to its perfection, it follows that the motion through which rest is produced is swifter the more it approaches rest, as is abundantly clear in natural motions.
But in things that are moved by force, the contrary happens, for the motion grows less intense the closer it gets to the state of rest. Consequently, forced rest is not generated. This is what he means when he says that some things come to rest by force without having become so, that is, in such a way that their rest is not generated.
744. He gives the second reason at moreover, “coming to a standstill” (230b26), and it is this: coming to a standstill, or the coming to be of rest, either is entirely the same as the natural motion by which something is carried to its natural place or is something that happens to accompany it.
Now, it is clear that both are the same reality, though differing in account. For the goal of a natural motion is to be in a natural place, but to be in a natural place and to be at rest in it are really the same thing.
Consequently, a natural motion and the coming to be of rest are the same thing in reality and differ only in account.
However, it is evident that forced rest is not brought about by a natural motion. Therefore, coming to a standstill is not present in forced states of rest; that is, such states are not generated.
745. Then, at “there is also another” (230b28), he raises a third question about a point mentioned above, that rest in something is contrary to motion from it. Now, this seems to be false, for when something is moved from a thing as from a place, or the thing is being abandoned (as in the case of a quality or quantity), while it is being moved, it still seems to have that which is cast off or left behind. For a thing does not leave its entire place all of a sudden, but successively; likewise, it is only gradually that it loses whiteness. Therefore, while it is being moved, it still retains something of the starting point. If, therefore, the state of rest whereby something remains in a starting point is contrary to the motion by which departure is made from it, it follows that two contraries are together—which is impossible.
746. So, he solves this difficulty at “but may we not say” (230b32). And he says that what is being moved by departing from its starting point is at rest in it not absolutely, but in a certain sense only, namely, in the sense that it is there not in its entirety, but partly, because it is universally true that, in all cases of motion, part of the mobile is in the terminus where, or from which, and part in the terminus to which. Nor is it unacceptable that one contrary be mixed with another in a certain respect; but the less it is mixed, the more perfectly is it contrary. Therefore, a motion is more contrary to another motion (since they are never intermingled) than a rest is, which somehow intermingles.
Finally, in summary, he says that we have spoken about motion and rest and how unity and contrariety are found therein.
747. Then, at “with regard to coming” (231a5), he states some things that will clarify the foregoing. These passages are said not to be found in the Greek text, and according to the Commentator, not even in the Arabic text; consequently, these statements seem to have been lifted from the sayings of Theophrastus or some other expositor of Aristotle.
Three things are here posited in an attempt to clarify the foregoing.
The first pertains to the question previously raised about the generation of unnatural rest. And he says that someone may wonder about coming to a standstill—that is, about the coming to be of rest: if all motions that are outside nature have an opposing state of rest, an unnatural one, does that state of rest come to a standstill, that is, come to exist? If it is held that there is no coming to a standstill in cases of forced rest, something unacceptable follows. For it is clear that a thing in motion by force will sometimes remain—that is, come to rest—by force. Consequently, it will follow that something will be at rest not eternally, without having come to rest—which seems impossible. But it is plain that sometimes there is forced rest. For just as things are moved outside their nature, so also they rest outside their nature. But it should be observed that what is said here appears contrary to what was said above (230b21; [743]). Hence, Averroes says that a solution is now being given to a question previously raised.
However, it is better to say that the previous doctrine contains more truth, although what is being said here is somehow true also. For forced rest is not, strictly speaking, generated in the sense that it proceeds from a cause that is essentially productive of rest, as happens when natural rests are generated.
But forced rest is generated per accidens through lack of a productive force, for when the force of the mover either ceases or meets an obstacle, the state of forced rest comes to be. This is why motions by force peter out at the end, but natural ones become more intense.
It should be noted also that there is another text for this place, to which we should give our attention. It reads: someone may ask whether to a motion outside nature there is any contrary rest not according to nature. This does not inquire whether, properly speaking, a state of rest that is contrary to nature is opposed to a motion that is contrary to nature, as Aristotle taught above; rather, here he is now speaking in wide and loose terms in the sense of the general opposition between rest and motion. And he says that it seems unreasonable not to find unnatural states of rest. For it is clear that the violence of the mover will remain, that is, will cease at some time, and unless rest eventuates, the motion will not come to a standstill. Hence, it is clear that forced motions are opposed to forced states of rest, because what is moved outside its nature rests outside its nature.
748. Then, at “further, some things have” (231a9), he mentions a second fact to explain his doctrine on the contrariety of natural and forced motion. He says that, since certain things are subject to motions that are according to nature and outside their nature, as fire is moved upward according to nature and downward outside its nature, the question arises whether the natural upward motion of fire has for its contrary the forced downward motion of fire or the natural downward motion of earth.
He answers that both are contrary to the natural upward motion of fire, but not in the same way. For the downward motion of earth is contrary to the upward motion of fire as something natural contrary to something natural, but a downward motion of fire is contrary to the upward motion of fire as something natural contrary to something by force. The same is true for the contrariety of states of rest.
749. Then, at “but there would seem” (231a16), he mentions a third point to explain what he previously said about contrariety of rest to motion. And he says that perhaps motion is not strictly opposed to rest, but only in some sense. For when someone is being moved from a place, in which he was at rest, and is putting it off, he seems to retain something of the place. Hence, if rest in this place is contrary to a motion from this place to a contrary place, it follows that contraries are together. But yet, a thing is somehow still at rest while it perseveres in A; indeed, speaking generally of a thing in motion, part of it is in the terminus from which and part in the terminus to which. Consequently, rest is less contrary to motion than a contrary motion is, as was explained above.
Finally, he sums up, as is clear of itself.
Now, the fact that the same words that appeared in an earlier passage (230b29) are repeated lends support to the possibility that they are not the words of Aristotle, but of some expositor.