Lecture 12 — Motion pertains to quantity, quality, and place

If the categories are divided into substance, quality, place, action, passion, relation, and quantity, there must be three kinds of motion, namely, of quality, of quantity, and of place.

There is no motion of substance, because substance has no contrary.

Nor is there motion of relation, for it is possible that, when one of two relative things has undergone a change, the other may be truly referred to under a new term even though it has not been changed in any way.

Hence, the motion of these relative things will be accidental.

Nor is there motion of agent or of patient as of mover and thing moved, because there is no motion of motion or generation of generation. There are two ways in which there might be motion of motion.

First, motion might be of the subject moved, as a man is moved because he is changed from white to black. Thus motion might be heated or cooled or might change its place or might increase. But this is impossible, for change is not a subject.

Second, some other subject might be changed from change to some other form of being, as a man might be changed from sickness to health. But this is possible only accidentally, for every motion is a change from one thing to something else. The same applies to generation and destruction, although the opposites involved in these changes are different from those of motion.

Therefore, a man changes at the same time from health to sickness, and from this change itself to another. And it is evident that, if a man has become ill, he will be changed into something else, whatever it may be (for he can come to rest).

Further, this will always be to some opposite which is not contingent, and that change will be from something to something else. Hence, its opposite will be becoming healthy, but this will happen accidentally. Likewise, there is a change from recollection to forgetting, because the subject to which forgetting belongs is changed—sometimes to a state of knowledge and sometimes to one of ignorance.

Further, the process will go on to infinity if there is change of change and generation of generation. Therefore, if the latter comes to be, the former must also. For example, if generation in an unqualified sense at one time was coming to be, that which is coming to be something was also coming to be.

Hence that which was coming to be in an unqualified sense did not yet exist, but there was something which was coming to be, or which has already come to be. Therefore, if this also at one time was coming to be, then, at that time, it was not coming to be something.

However, since there is no first term in infinite things, neither will there be a subsequent one. Hence it is impossible for anything to come to be or be moved or be changed in any way.

Further, of the same thing of which there is contrary motion and rest, there is also generation and destruction.

Hence, when that which is coming to be becomes that which is coming to be, it is then being destroyed. For it is not destroyed as soon as it is generated or afterward, for that which is being destroyed must be.

Further, there must be some matter underlying the thing which is coming to be or being changed. What, then, will it be that becomes motion or generation in the same way that a body or a soul or something else of this kind is alterable? Further, what is the thing to which motion proceeds?

For motion must be of this particular thing from this to that, and yet the latter should not be a motion at all. In what way, then, is this to take place? For there can be no learning of learning, and therefore no generation of generation (1067b12–1067b21).

And since there is no motion of substance or of relation or of action or of passion, it follows that there is motion of quality, of quantity, and of location; for each of these admits of contrariety. By “quality,” I mean not that which comes under the category of substance (for even difference is quality), but the passive power in virtue of which a thing is said to be acted upon or to be incapable of being acted upon.

The immovable is what is totally incapable of being moved, or what is moved with difficulty over a long period of time or begins to be moved slowly, or what is naturally fit to be moved but is not capable of being moved when it is so fit, and where, and in the way in which it would naturally be moved.

And this is the only kind of immobility which I call rest, for rest is contrary to motion. Hence, it will be the privation of what is receptive of motion.

2376. Having divided change into generation, destruction, and motion, here he subdivides the other member of this division (namely, motion) on the basis of the categories in which it takes place. In regard to this, he does two things.

First (1068a8; [2376]), he indicates the categories in which motion can be found.

Second (1068b20; [2401]), he explains the different senses in which the term immovable is used, at the immovable.

In regard to the first, he does three things.

First, he sets forth his thesis.

Second (1068a10; [2378]), he proves this, at there is no motion.

Third (1068b15; [2399]), he draws his main conclusion, at and since.

He accordingly first says (1068a8) that, since the categories are divided into substance, quality, and so on, and since there cannot be motion in the other categories, there are therefore three categories of being in which motion can be found. These are quality, quantity, and location, for which he substitutes the term “place,” since location merely signifies being in a place: to be moved with respect to place is merely to be moved with respect to one’s location. For motion with respect to place is not attributed to a subject in which place inheres, but to the thing in place.

2377. Now it should be noted that he seems to omit three categories, namely, “when,” posture, and outfitting. For, since “when” signifies being in time, and time is the measure of motion, the reason why there is no motion in the category of temporal situation or in that of action and of passion, which signify motion itself under special aspects, is the same. And posture adds nothing to location except a definite arrangement of parts, which is nothing else than a definite relationship of parts to each other. And outfitting implies the relation of one clothed to his clothing. Hence, the reason why there does not seem to be motion with respect to posture, outfitting, and relation seems to be the same.

2378. There is no motion of substance (1068a10). Next, he proves his thesis, and in regard to this, he does three things.

First (1068a10; [2378]) he shows that there is no motion with respect to substance;

second (1068a11; [2385]), that there is no motion with respect to relation, at nor is there motion of relation;

third (1068a13; [2386]), that there is no motion with respect to action and passion, at nor is there motion of agent.

He accordingly first proves (1068a10) that there cannot be motion with respect to substance, because motion is a change from subject to subject. Therefore, the two subjects between which there is motion are either contraries or intermediates. Hence, since nothing is contrary to substance, it follows that there cannot be motion with respect to substance, but only generation and destruction, whose limits are opposed to each other as contradictories and not as contraries, as has been stated above (1067b21; [2366]).

2379. Now, it seems that his statement that substance has no contrary is false, because fire clearly appears to be contrary to water, and because Aristotle had proved in On the Heavens 1 that the heavens are not destructible, since they do not have a contrary, whereas other bodies, which are corruptible, have a contrary.

2380. Hence, some said that there is nothing contrary to the whole composite substance, because the subject of contraries must be one; but nothing prevents a substantial form from having a contrary. For they said that heat is the substantial form of fire. But this cannot be true, because substantial forms are not perceptible of themselves. And, again, it is evident that, in other bodies, heat and cold are accidents. But what belongs to the category of substance cannot be an accident in anything.

2381. Others have said that heat and cold are not the substantial forms of fire and water, but that their substantial forms are contraries differing in degree and are intermediate, so to speak, between substance and accidents. But this is wholly unreasonable, for since form is the principle of a species, if the forms of fire and of water are not truly substantial, neither are fire and water true species in the category of substance. It is impossible, then, that there should be an intermediate between substance and accidents, because they belong to different categories, and between such things, an intermediate does not fall, as has been shown above in book 10 (1057a33; [2102]), and also because the definitions of substance and accident have no intermediate. For a substance is a being of itself, whereas an accident is not a being of itself, but has being in something else.

2382. It is necessary, then, to say that substantial forms cannot be contraries, because contraries are extremes of a certain definite distance, and in a sense, they are continuous, since motion is from one contrary to another. In those categories, then, in which no such continuous and definite distance is found, it is impossible to find a contrary, as is clear in the case of numbers. For the distance between one number and another does not mean continuity, but the addition of units. Hence, number is not contrary to number, nor similarly is figure contrary to figure.

2383. The same thing applies to substances, because the intelligible structure of each species consists in a definite unity. But, since form is the basis of difference, if substantial forms are not contrary to each other, it follows that contrariety cannot be found between differences.

2384. It is necessary to say, then, that a substantial form, considered in itself, constitutes a species in the category of substance, but that, according as one form implies the privation of another, different forms are the principles of contrary differences. For in one respect, a privation is a contrary, and living and non-living, rational and irrational, and the like are opposed in this way.

2385. Nor is there motion of relation (1068a11). Next, he shows that there is no motion in the proper sense in the category of relation except accidentally. For just as a thing is moved accidentally when motion takes place in it only as a result of something else being moved, in a similar way, motion is said to be accidental to a thing when it takes place in it only because something else is moved. Now, we find this in the category of relation, for unless something else is changed, it is not true to say that change occurs in relation. For example, the unequal comes from the equal only when there has been change in quantity. Similarly, the like comes from the unlike only when there has been a change in quality. Thus, we see that one of two relative things is said to be changed when change affects the other one of them; for example, a thing which is unmoved of itself changes from left to right when some other thing changes its place. Hence it follows that there is motion in the category of relation only accidentally.

2386. Nor is there motion of agent (1068a13). Here he shows that motion does not occur with respect to either action or passion. He proves this by four arguments.

The first is as follows. Action and passion constitute motion and designate it. If, then, motion were to occur in action and in passion, it would follow that there would be motion of motion and generation of generation and change of change. But this is impossible. Therefore, it is also impossible that there should be motion in action and in passion. That it is impossible for motion to be moved he proves thus.

There are two ways in which there might be motion of motion: first, there might be motion of motion as of a subject which is moved; second, as of the limit of motion.

And motion might be the subject of motion, as we say that there is motion of a man because a man is moved because he is changed from white to black. In a similar way, motion would be moved, and would be either heated or cooled, or changed with respect to place, or increase. But this is impossible, because motion cannot be the subject of heat or of cold or of similar attributes. It follows, then, that there cannot be motion of motion if motion is regarded as a subject.

2387. But neither can there be motion of motion as of a limit, some other subject being changed from one species of change to another, as a man might be changed from sickness to health. For this is possible only accidentally.

2388. Hence, he shows next that it is impossible for motion to be moved per se, because every motion is a change from one thing to something else. Similarly, generation and destruction are a change from one thing to something else, even though, in their case, the limits of change are not opposed to each other as they are in that of motion, as has been said above (1067b12; [2363]). If, then, there is change from one change to another, as from becoming sick to some other process of change, it will follow that, while a thing is being changed from health to sickness, it is being changed at the same time from that change to another, because, while one of the limits of a change is arising, a change from one limit to another occurs. Thus, if two processes of change are the limits of one change, it follows that, while the original change is occurring, a change into another takes place. And so, at the same time that a thing is being moved from health to sickness, it will be being changed from becoming healthy to some other change.

2389. But this seems to be true only inasmuch as one change succeeds another. And it is possible that any other change may succeed this one by which something is being moved from health to sickness—for example, becoming white or becoming black or change of place or any other change. Hence, it is evident that, if someone is becoming ill because he is being moved from health to sickness, he can be changed from this change to any other. Nor is this surprising, because he can even be changed from this change to a state of repose, for it is possible that someone might come to rest after this change.

2390. But, since every change will always be to some opposite which is not contingent, that is, an opposite which cannot be true at the same time as the opposed term, it follows that, if there is a change from change to change, it will always be to an opposite change, which he calls not contingent. And that change in which the transition takes place will have to be from one thing to something else. Hence, the transition from a change of becoming ill will only be to the opposite change, which is called becoming healthy.

2391. And so two contrary positions seem to follow, namely, that an opposite change passes from one change to any other, and only to its opposite. And from this, it further follows that, at the same time that something is being changed to one of its opposites, it is also being changed to a change as if it were another opposite. This seems to be impossible, for it would follow that nature inclines to opposite effects at the same time. Hence, it cannot be that anything is changed per se from one change to another.

2392. But this can happen accidentally. For example, a person may change from recollection to forgetfulness because the subject is changed, sometimes in relation to one extreme and sometimes to the other—not that it may be the mover’s intention that, at the same time that he is being changed to one extreme, he is intending to move to the other.

2393. Further, the process (1068a33). Then he gives the second argument, which runs thus. If there is change of change, as limit of limit, or generation of generation, one change must be reached only by another change, as one quality is reached only by a preceding alteration. Thus, it will be possible to reach that preceding change only by a prior change, and so on to infinity.

2394. But this cannot be the case, for if it is assumed that there are an infinite number of changes related in such a way that one leads to the other, the preceding must exist if the following does.

Let us suppose that there is a particular instance of the generation of a generation in an unqualified sense, which is the generation of substance. Then, if the generation sometimes comes to be in an unqualified sense, and (again) if the coming to be of generation in an unqualified sense itself at one time came to be, it will follow that that which is coming to be in an unqualified sense did not yet exist, but there was generation in one respect—namely, the very generation of the process of generation. And if this generation also came to be at some time, since it is not possible to have either an infinite regress or any first term among infinite things, it is impossible ever to come to any first process of generation.

But, if the preceding member in a series does not exist, there will be no succeeding member, as has been pointed out above, and the consequence will be that neither will there be a subsequent one, that is, one which follows it. It follows, then, that nothing can come to be or be moved or be changed. But this is impossible. Hence change of change is impossible.

2395. Further, of the same thing (1068b6). Then he gives the third argument, which is as follows. Contrary motions, rest and motion, and generation and destruction belong to the same subject, because opposites are suited by nature to come to be in the same subject. Therefore, if some subject is being changed from generation to destruction, at the same time that it is being generated, it will be undergoing change leading to destruction, which is to be changed into non-being (for the terminus of destruction is non-being). Now, what is being changed into non-being is being destroyed. Hence, it follows that a thing is being destroyed at the same time that it is being generated.

2396. But this cannot be true, for while a thing is coming to be, it is not being destroyed, nor is it corrupted immediately afterward. For, since destruction is a process from being to non-being, that which is being destroyed must be. And thus there will have to be an intermediate state of rest between generation, which is a change to being, and destruction, which is a change to non-being. Hence, there is no change from generation to destruction.

2397. Further, there must be (1068b10). Then he gives the fourth argument, which runs as follows. In everything that is being generated, two things must be present: first, the matter of the thing which is generated; second, that in which the generation is terminated.

If, then, there is generation of generation, both generation and motion will have to have some matter, such as an alterable body or a soul or something of this kind. But it is impossible to assign matter of this kind to generation and to motion.

2398. Similarly, there must also be something in which the process of change is terminated, because some part—namely, the matter of the thing generated—must be moved from one attribute to another, and that in which motion is terminated cannot be motion, but is the terminus of motion. For of the kind of change which we call learning, there is not some other learning which is terminated in it, which is a learning of learning. Hence, there is nothing to conclude but that there is no generation of generation.

2399. And since (1068b15). Here he draws as his conclusion his main thesis. He says that, since there cannot be motion either in the category of substance, or in that of relation, or in that of action and passion, it follows that motion belongs to quality, quantity, and location. For in these categories, there can be contrariety, which stands between the termini of motion, as has been pointed out.

2400. But since “quality” is sometimes used to mean substantial form, he adds that, when there is said to be motion in quality, it is not understood to signify substance, in view of the fact that substantial difference is predicated as something qualitative; but it refers to the kind of quality by which something is said to be acted upon or to be incapable of this. For there is alteration, properly speaking, only in terms of susceptible qualities, as is proved in Physics 7.

2401. The immovable (1068b20). Then he explains the different senses in which the term “immovable” is used, and he gives three of these.

First, the immovable means what is completely incapable of being moved, as God is immovable.

2402. Second, it means what can be moved with difficulty, as a huge boulder.

2403. Third, it means what is naturally fit to be moved but cannot be moved when it is fit, and where, and in the way in which it is fit to be moved. And only this kind of immobility is properly called “rest,” because rest is contrary to motion. Hence, rest must be the privation of motion in what is susceptible of motion.