Lecture 11 — Motion and change

Either everything which is changed is changed accidentally (as when we say that a musician walks) or it is changed without qualification because something belonging to it is changed (as what is changed in some of its parts)—for example, the body is said to be healed because the eye is. And there is some primary thing which is moved of itself, and this is what is per se movable.

The same division applies to a mover, for it causes motion either accidentally or in some part of itself or per se.

And there is a primary mover and something which is moved. And there is also a time in which it is moved, and something from which it is moved, and something to which it is moved. But the species and modifications and place to which things in motion are moved are immovable, as science and heat. Heat is not motion, but heating is.

Now, change which is not accidental is not found in all things, but between contraries and between their intermediates and between contradictories. We may be convinced of this by induction. Whatever is changed is changed either from a subject to a subject, or from a non-subject to a non-subject, or from a subject to a non-subject, or from a non-subject to a subject. And by “subject,” I mean what is expressed by an affirmative term. Hence there must be three changes—for to go from a non-subject to a non-subject is not change, because there is no opposition, since the limits are neither contraries nor contradictories.

The change from a non-subject to a subject which is its contradictory is generation. If it is unqualified, it is generation in an unqualified sense, and if in a part, partial generation. The change from a subject to a non-subject is destruction.

If non-being has several different meanings, then neither that which involves a combination or separation of terms nor that which refers to potency and is opposed to being in an unqualified sense is capable of being moved (for what is not-white or not-good can be moved only accidentally, since what is not-white may be a man).

But non-being in an unqualified sense cannot be moved in any way, because it is impossible for non-being to be moved. And if this is so, generation cannot be motion, because non-being is generated.

For even if it is most certainly generated accidentally, it will still be true to say that what is generated in an unqualified sense is non-being. The same argument applies to rest. These are the difficulties, then, which result from this view.

And if everything moved is in a place, though non-being is not in a place, it would have to be somewhere.

Nor is destruction a motion, for the contrary of motion is motion or rest, but the contrary of destruction is generation.

And since every motion is a kind of change, and the three changes are those described (1067b12), and of these, those which refer to generation and destruction are not motions, and these are changes between contradictories, only change from a subject to a subject must be motion. And the subjects are either contraries or their intermediates; for even privation is given as a contrary and is expressed by an affirmative term, such as naked or toothless or black.

2355. Having explained what motion is, and having dealt with the infinite, which is a certain attribute of motion, here the Philosopher establishes the truth about the parts of motion. This is divided into two parts.

In the first (1067b1; [2355]), he distinguishes the parts of motion,

and in the second (1068b26; [2404]), he explains the connection between motion and its parts, at things that are.

The first is divided into three members, corresponding to the three divisions which he makes in motion, although one of these is included under the other as a subdivision of the preceding division.

In regard to the first, he does two things.

First, he divides motion with regard to the thing moved;

second (1067b6; [2358]), with regard to a mover, at the same division.

He accordingly first says (1067b1) that a thing may be changed in three ways.

In one way, a thing may be changed only accidentally, as when something is said to be changed because the thing to which it belongs is changed, whether it belongs to it as an accident to a subject (as when we say that a musician walks), or as a substantial form to matter (as the soul belongs to the body which is moved), or as a part is said to be moved when the whole is moved, or as something contained is moved when its container is moved (as a sailor is said to be in motion when his ship is in motion).

2356. In a second way, a thing is said to be changed without qualification because some part of it is changed, as those things that are moved in some part. For example, the body of a man is said to be healed because the eye is. This is to be moved per se, but not in the first way.

2357. In a third way, a thing is said to be moved primarily and of itself, as when some whole is moved in its totality—for example, when a stone is moved downward.

2358. The same division (1067b6). He then gives the same division with regard to a mover, for a thing is said to be a mover in three ways.

First, a thing is said to cause motion accidentally, as when a musician builds.

2359. Second, a thing is said to be a mover in regard to some one of its parts, as when a man strikes and injures someone with his hand.

2360. Third, a thing is said to be a mover per se, as when fire heats and a physician heals.

2361. And there is (1067b7). Then he gives a second division of motion or change, and in regard to this, he does three things.

First (1067b7; [2361]), he prefaces his discussion with certain points which are necessary for an understanding of the division of motion.

Second (1067b12; [2363]), he divides motion, at now, change.

Third (1067b21; [2366]), he explains the division of change, at the change.

He first says that there are five things found in every change:

first, there is a primary mover;

second, something which is moved;

third, a time during which the motion takes place, because every motion occurs in time;

fourth, a starting point from which motion begins;

and fifth, a terminus to which the motion proceeds.

However, motion or change is not divided into species on the basis of neither the mover, nor of the thing moved, nor of time, because these are common to every change, but it is divided on the basis of the starting point from which it begins and the terminus to which it proceeds.

2362. He therefore explains the last two, saying that the species, that is, forms, and modifications, that is, qualities, and place are limits of motion, since those things that are movable are moved with respect to these. He uses the term “species” because of generation; “modifications” because of alterations; and “place” because of local motion. He gives examples of modifications by using science and heat. And because it might seem to some that heat is the same as alteration, and then it would follow that heat is motion and not a limit or terminus of motion, he therefore says that heat is not motion, but heating is.

2363. Now, change (1067b12). Then, passing over two parts of the first division, he takes the third, namely, change which is neither accidental nor in a part, and subdivides it according to its limits. He says that change which is not accidental is not found between just any limits whatever. Its limits must be either contraries, as change from white to black, or intermediates, as change from black to red and from red to gray. There is also change between contradictories, as from white to not-white (and vice versa). He says nothing of privative opposites because they are found between contradictories and contraries and are understood to come under these.

2364. He shows by induction that change takes place only between the above-mentioned limits. Now, the limits of change admit of four possible combinations.

First, when both limits are affirmative or positive terms, as when something is said to be changed from white to black, and this change he describes as one from a subject to a subject.

Second, when both limits are negative terms, as when something is said to be changed from not-white to not-black, or in his words, from a non-subject to a non-subject.

Third, when the starting point from which change begins is a positive term and the terminus to which it proceeds is a negative one, as when a thing is said to be changed from white to not-white, or as he says, from a subject to a non-subject.

Fourth, when the starting point of change is a negative term and the terminus to which it proceeds is a positive one, as when a thing is said to be changed from not-white to white, or as he says, from a non-subject to a subject. He explains the meaning of the term “subject,” which he had used, as what is signified by an affirmative or positive term.

2365. Now, one of these four combinations is useless. There is no change from a non-subject to a non-subject, because two negative terms—such as not-white and not-black—are neither contraries nor contradictories, since they are not opposites. For they can be affirmed truly of the same subject, because there are many things that are neither white nor black. Hence, since change is between opposites, as is proved in Physics 1, it follows that there is no change from a non-subject to a non-subject. Therefore, there must be three kinds of change, two of which relate to contradiction and the other to contrariety.

2366. The change (1067b21). Then he shows what these three changes are, and in regard to this, he does three things.

First, he shows that generation and destruction are two of these.

Second (1067b25; [2368]), he shows that neither of these is motion, at if non-being.

Third (1068a1; [2375]), he draws his conclusion as to which change is called motion, at and since every.

He accordingly first says (1067b21) that, of the three changes mentioned above, that which is from a non-subject to a subject, or between contradictory terms, is called generation. And this is twofold.

Either there is change from non-being in an unqualified sense to being in an unqualified sense, which is generation in an unqualified sense (and this occurs when a movable subject is changed substantially),

or there is change from non-being to being, not in an unqualified sense, but in a qualified one, such as change from not-white to white, which is generation in a qualified sense.

2367. But that change which proceeds from a subject to a non-subject is called destruction. In this change, we also distinguish between destruction in an unqualified sense and in a qualified one, just as we did in the case of generation.

2368. If non-being (1067b25). Then the Philosopher shows that neither of these changes is motion.

First (1067b25; [2368]), he shows that this is true of generation;

second (1067b36; [2374]), that it is true of destruction, at nor is destruction.

He accordingly says, first (1067b25), that the term “non-being” is used in the same number of senses as “being” is. One meaning is the combination and separation found in a proposition. Since this does not exist in reality, but only in the mind, it cannot be moved.

2369. Being and non-being are used in another sense with reference to act and potency. That which is actual is a being in an unqualified sense, but that which is potential only is a non-being. He therefore says that, even that sort of non-being which is a being potentially, but not actually, cannot be moved.

2370. He explains why he had said that actual non-being is opposed to being in an unqualified sense, when he adds for what is not-white. For potential being, which is opposed to actual being and is not being in an unqualified sense, can be moved, because what is not not-white actually or not-good actually can be moved, but only accidentally. For what is moved is not the not-white itself, but the subject in which this privation is found, and this is an actual being. For that which is not white may be a man, but that which is an actual non-being in an unqualified sense—that is, in substance—cannot be moved at all. Now, if all of these statements are true, I say that it is impossible for non-being to be moved. And if this is the case, generation cannot be motion, because non-being is generated. For generation, as has been pointed out (1067b21; [2366]), proceeds from non-being to being. Hence, if generation in an unqualified sense were motion, it would follow that non-being in an unqualified sense would be moved.

2371. But one can raise an objection to this process of reasoning by saying that non-being is generated only accidentally, for the subject of generation; that is, a being in potency, is generated per se. But non-being signifies privation in a matter. Hence, it is generated only accidentally.

2372. For even if (1067b32; [2366]). Then he refutes this objection. He says that, even if a being is generated only accidentally, nevertheless it is true to say that what is generated in an unqualified sense is non-being. And of each of these it is true to say that it cannot be moved. Similarly, it cannot be at rest, because non-being in an unqualified sense is neither in motion nor at rest. These are the untenable results if one maintains that generation is motion.

2373. In order to show that non-being is not moved, he adds that everything that is moved is in a place because local motion is the first of all motions, whereas non-being in an unqualified sense is not in a place, for it would then be a being somewhere. Hence it cannot be moved; therefore, generation is not motion.

2374. Nor is destruction (1067b36). From these considerations, he further shows that destruction is not motion, for the only thing that is opposed to motion is motion or rest. But destruction is opposed to generation. Therefore, if destruction were motion, generation would have to be either motion or rest. But this cannot be true, as has been shown.

2375. And since every motion (1068a1). Next he shows which change is said to be motion. He says that every motion is a kind of change. But there are only three changes, and two of these, which involve contradictories—generation and destruction—are not motion. It follows, then, that only change from a subject to a subject is motion. And since the subjects between which motion takes place must be opposed to each other, they must be contraries or intermediates, for even though a privation is expressed by an affirmative term, such as naked, toothless, and black, it is regarded as a contrary, because privation is the primary contrariety, as has been pointed out in book 10 (1055b11; [2049]). And he says that black is a privation not in an unqualified sense, but inasmuch as it participates deficiently in the nature of its genus.