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.

About this, he does two things:

first, he raises questions and solves them;

second, he explains certain matters that may still be doubtful in regard to these questions, at with regard to coming (231a5; [747]).

The first part is divided into three sections, one for each question he raises.

About the first point he does two things:

first, he raises a question;

second, he solves it, at we answer that, if (230a29; [740]).

738. Therefore he first (230a18) raises the question why it is that, in the genus of local motion, but not in the other genera, there are found some motions and rests that are according to nature and some outside of nature. For example, why is it that there are alterations according to nature but none outside of nature? For getting well does not seem to be according to nature or outside of nature any more than getting sick, since each originates from a natural intrinsic principle. The same is true in regard to turning white and turning black or in growing and decreasing, for the former motions are not so contrary to one another that one is according to nature and the other outside of it, since each is a natural process. Nor is one growing contrary to another growing in such a way that one is according to nature and the other outside of it. The same is true of generation and ceasing to be, for generation cannot be said to be according to nature and ceasing to be outside of it, for growing old—which is the road to ceasing to be—is according to nature. Nor does it appear that one generation is according to nature and another outside of it.

739. Now, it seems that what he says here is opposed to a declaration in De caelo 2.6 that old age and every defect and ceasing to be are against nature. (Cf. St. Thomas, Commentary on De caelo, bk. 2, lect. 9.) But it must be said that old age and ceasing to be and decreasing are against nature in one sense and according to nature in another. For if we consider the specific nature of anything—that is, its particular nature—it is clear that all ceasing to be and all defects and decrease are against nature, because each thing’s nature tends to preserve the subject in which it exists, whereas the contrary of this happens when the nature is weak or defective.

But, if we consider nature in general, all these things are the result of a natural intrinsic principle, as the destruction of an animal results from the contrariety of hot and cold; and the same is true for all the others.

740. Then, at we answer that, if (230a29), he answers this question by invalidating it.

About this, he does two things:

first, he shows that things according to nature and outside of nature are found in every genus;

second, he shows how these two things are contrary when they occur in motions and in states of rest, at now, motions and states (230b10; [742]).

About the first, he does two things:

first, he determines the truth;

second, he removes an objection, at but it may be objected (230b6; [741]).

He says first (230a29) that, since what takes place through force is outside of nature (because force arises from a principle outside a thing in such a way that the thing suffering force does not cooperate, whereas what is natural comes from an intrinsic principle), it follows that forced ceasing to be is contrary to natural ceasing to be, just as a ceasing to be that is outside of nature is opposed to one according to nature.

According to the same argument, he concludes that some generations are by force and not according to fate—that is, not according to the order of natural causes (because the order of natural causes can be called “fate”)—as when a person grows roses or fruits by artificial means out of season or when the generation of frogs or other natural things is procured artificially. Consequently, since these generations are by force, they are outside of nature and are contrary to generations according to nature.

He shows the same for growing and decreasing. For some cases of growth are by force and outside of nature, as is evident in persons who reach the state of puberty in an abnormally short time on account of soft living or on account of their food; that is, they are fed abundantly and delicately. The same is also apparent in the growing of wheat, for sometimes the grains grow unnaturally through abundance of moisture and are not compact (that is, made thick and solid by normal digestion).

It is likewise in alterations. Some are by force and some natural, as is especially evident in the process of getting well. For some recover from fever on the critical days and some not on the critical days. The former are cured according to nature and the latter outside of nature.

741. Then, at but it may be objected (230b6), he raises an objection against the foregoing. For since what is outside nature is contrary to what is according to nature, if there are some generations that are according to nature and some not (and the same for ceasing to be), it follows that instances of ceasing to be are contrary not to generation, but to one another, because one thing cannot be contrary to two.

But he solves this by saying that there is nothing to prevent generation from being contrary to generation and ceasing to be to ceasing to be. This is true even if you were to abstract from the contrariety between what is according to nature and what is outside of nature.

For if you take the case of something sweet coming to be and then ceasing to be, and the case of something sad coming to be and ceasing to be, the two cases of coming to be would be contrary and the two of ceasing to be would be contrary.

When he speaks of the coming to be and the ceasing to be of the sweet, he means when something more noble comes to be from the less noble that has ceased to be, as when fire is generated from air;

on the other hand, the coming to be and ceasing to be of the sad refers to the less noble coming to be from the ceasing to be of the more noble, as when air is generated from fire.

Now, even though ceasing to be is contrary to ceasing to be, it does not follow that it is not opposed to coming to be, for ceasing to be is opposed to coming to be when both are taken generically, while ceasing to be is opposed to ceasing to be in a specific sense. For example, avarice is contrary to liberality in the way that a vice is contrary to a virtue, but it is opposed to prodigality as one species to another. Thus, what he concludes is that ceasing to be is contrary to ceasing to be not simply—that is, in a generic sense (Cf. lect. 9, n. 728.)—but one ceasing to be is this and another that—that is, by force and outside of nature, or sweet and sad.

742. Then, at now, motions and states (230b10), he explains contrariety in motion and rest on the basis of their being outside nature and according to nature. And he says that not only is coming to be contrary to coming to be and to ceasing to be from the viewpoint of being outside nature and according to nature, but all motions and rests are in general contrary in this way. For example, an upward motion is contrary to a downward one (because up and down are contrarieties of place), and each of these motions is natural to certain bodies: fire is naturally carried upward, and earth downward.

And, again, in regard to each of these motions, one can take as contrary differences that which is according to nature and that which is outside of nature. And this is what he means when he says contrary to one another, namely, that the motions are differences; or he might mean that, in respect to the very bodies that are moved, there are contrary differences in their motions, namely, according to nature and outside their nature. For an upward motion is natural to fire, but a downward is outside of nature.

So, it is clear that a motion that is according to nature is contrary to one that is outside of nature. It is likewise for states of rest. For rest that is above is contrary to a downward motion. But rest above is not natural to earth, whereas a downward motion is. According to the foregoing, then, it is clear that rest that is outside of nature is contrary to the natural motion of the body involved, for even in the same body, motions are mutually contrary in the sense that the natural motion of one body is contrary to an unnatural motion of the same body. The same is true of rest, for some contrary rests will be according to nature, as rest above for fire and rest down for earth; others are outside of nature, as down for fire and up for earth.

743. Then, at here, however, the question arises (230b21), he raises the second question: has every state of rest that is not eternal a becoming, which becoming is called a coming to a standstill? This is done so that we will not understand coming to a standstill and “being at rest” to mean the same thing. Rather, coming to a standstill means “to arrive at a state of rest.” This perhaps sounds better in Greek.

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. (Lect. 9, n. 729.) 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.