BOOK V

Lecture 1

Per se notion is distinguished from per accidens

638. After discussing motion and the things that accompany motion in general, the Philosopher now undertakes to give various divisions of motion. And his treatment falls into two parts:

In the first he divides motion into its species;

In the second he divides motion into quantitative parts in Book VI.

In the first he makes two parts:

First he divides motion into its species;

Secondly, he discusses unity and opposition of motion, at L. 5.

The first is divided into two sections:

In the first he distinguishes motion per se from per accidens;

In the second he divides motion into its species, at L. 2.

The first is divided into two parts:

In the first he distinguishes per se motion from per accidens;

In the second he shows that per accidens need not be discussed but that per se motion must, at 647.

In regard to the first he does two things:

First he distinguishes per se from per accidens motion;

Secondly, he makes a summary at 646.

In the first part he distinguishes per se motion from per accidens motion in three ways:

First, on the side of the mobile;

Secondly, on the side of the mover, at 640;

Thirdly, on the side of the termini of motion, at 641.

639. He says therefore first (465) that whatever changes, i.e., whatever is being changed, is described as doing so in three ways. First, per accidens, as when we say that a musician is walking, because the person who is walking happens to be a musician. Secondly, a thing is described as being changed without qualification even though only some part of it is changing, i.e., in statements which refer to part of the thing in question: thus the body is said to be restored to health, because the eye or the chest, which are parts of the body, are restored to health. Thirdly, there is the case of a thing that is in motion neither accidentally nor in respect of something that belongs to it as a part but in virtue of its being directly and per se in motion. And he says “directly” to exclude motion of a part, and per se to exclude motion that is per accidens. Now this per se mobile is a different thing according to the various kinds of motion: for example, it may be a thing capable of alteration—in which case it is called alterable—or it may be capable of growing—in which case it is called augmentable. Again, in the sphere of alteration it is called heal-able, if it is moved in respect of health, and heat-able, if it is moved in respect of heat.

640. Then at (466) from the side of the mover he distinguishes per se from per accidens motion, And he says that the preceding distinctions which were posed from the side of the mobile can be found in the mover. For a thing is described in three ways as causing motion. First, per accidens, as “the musician is building”. Secondly, by reason of a part (when some part of the mover causes motion), e.g., the man is said to strike, because his hand strikes. In a third way, something is described as acting or moving directly and per se, as “the healer heals”.

641. Then at (467) looking at the terminus of motion, he divides motion once more in the same manner.

First he lays down some presuppositions;

Secondly, he gives his division, at 645.

About the first he does three things:

First he declares how many things are required for motion;

Secondly, he mutually compares them, at 642;

Thirdly, he settles a question, at 644.

He says therefore (467) that five things are needed for motion, First, there must be a first mover, i.e., a source from which the motion originates; secondly, a mobile that is being moved; thirdly, a time in which the motion occurs. In addition to these three are required the two termini; one from which the motion starts and another into which the motion tends; for every motion is from something into something.

642. Then at (468) he compares these five things:

First he compares the mobile to the two termini;

Secondly, he compares one terminus with the other, at 643,

He says therefore (468) that whatever is being moved directly and per se is distinct from the terminus into which the motion tends and from the terminus from which the motion begins, as is evident in these three things: wood, hot and cold. For in the motion called heating, the wood is the mobile subject, whereas the hot which is the terminus into which, is something else, as is the cold, which is the terminus from which.

Now he says that what is moved directly is distinct from both termini, because there is nothing to prevent what is being moved per accidens from being either of the termini: for a subject, such as wood, is what becomes hot per se; but the privation, which is a contrary, namely, cold, is what becomes hot per accidens, as was explained in Book I.

That the mobile is distinct from each terminus he proves on the ground that motion is in its subject, for example, in the wood, and not in either of the termini, i.e., not in the species “white” or in the species “black”. This is clear from the fact that that in which the motion exists is what is being moved. But the terminus of motion neither moves nor is moved: whether the terminus be a quality, as in alteration, or a place, as in local motion, or quantity, as in the motion called growing and decreasing. However, the mover moves the subject, which is being moved, into the terminus ad quem, Therefore, since motion exists in the subject being moved but not in the termini, it is clear that the mobile subject is distinct from the termini of the motion,

643. Then at (469) he compares one terminus with the other. And he says that a change gets its name from the terminus ad quem rather than from the terminus a quo; for example, a change into non-being has the special name “corruption’, while, on the other hand, “generation” is the change into being, even though it starts from non-being. Consequently, the name “generation” pertains to being and “corruption” to non-being. The reason for this is that through change the terminus a quo is taken away, but a terminus ad quem is acquired: for which reason, motion seems to have a repugnance for the terminus a quo and a kinship to the terminus ad quem —that is why it gets its name from the latter.

644. Then at (470) he settles a doubt, About which he does three things:

First, he mentions two things that are clear from the foregoing: first, that we have already pointed out in Book III what motion is; secondly, that in the immediately foregoing we have said that qualities and place and passible qualities that are the termini of motion are not themselves being changed, since there is no motion existing in them, as we have already said and as is clear from heat, which is a passible quality, and from science, which is a quality.

Secondly, at (471) he mentions a matter about which there is doubt, saying that someone may wonder whether passible qualities, such as heat and coldness and whiteness and blackness might not be types of motion, since none of them is a subject of motion.

Thirdly, at (472) he mentions a discrepancy that would arise if such a view were posited. For since whiteness is a terminus into which a motion tends, then if whiteness itself were a motion, it would follow that there is motion in the terminus of a motion, which cannot be, as will be proved later. And from this he arrives at the truth that it is not whiteness but whitening that is motion, But he adds “perhaps” because he has not yet proved that a motion cannot end up in a motion.

645. Then at (473) from the fact that termini of motion are distinct from the mover and from the mobile, he shows that in addition to the divisions of motion taken on the side of the mover and of the mobile, there is a third, i.e., one taken on the side of the terminus. And since it is from the terminus ad quem rather than from the terminus a quo that motions are named, he develops his division not on the side of the latter but of the former. And he says that even on the side of the termini it is possible to find in motion (1) a goal that is so per accidens or (2) partially, i.e., with reference to a part or to something other than itself or (3) directly and not with reference to something else.

And first of all, per accidens: when it is said of what is becoming white that it is being changed into something that can be understood or recognized by someone—that will be per accidens for it is accidental to the color white that it is recognized.

But if it is said of what is becoming white that it is being changed into a color—this will be according to a part: for it is said to be changing into a color because it is becoming white, which is a part of the genus color. Likewise, if I should say of someone who is going to Athens that he is going to Europe, for Athens is a part of Europe.

However, if it is said of what is becoming white that it is being changed into the color white, this will be directly and per se.

The Philosopher does not divide motion from the viewpoint of time (which was one of the five things required for motion) because time is related to motion as an extrinsic measure.

646. Then at (474) he summarizes what he has said. And he says that it is clear how something is in motion per se and how per accidens and how in respect of something not its entire self, i.e., in respect of a part, and again how what is referred to as directly and per se is found both in the mover and in the mobile, For it has been said what a direct and per se mover is and also what is being moved directly and per se. Finally, we have said that there is no motion in the quality which is the terminus of motion; rather motion is in what is being moved, i.e., in the actually mobile, which is the same thing.

647. Then at (475) he shows which kind of motion needs to be discussed.

First he states his proposition;

Secondly, he explains something he said, at 648.

He says therefore first that per accidens change will not be the subject of our discussion, whether it be per accidens on the side of the mover or of the mobile or of the terminus. The reason for this is that per accidens motion is indeterminate: for it is present in all things, in all termini, in all times, in all subjects and in all movers, and an infinity of things can be per accidens in something. But a change that is not per accidens is not found in all things; it is found only in situations (1) that involve contraries or the intermediate between contraries in respect to motions that affect quantity, quality and place, or (2) that involve contradictories, for example, generation and corruption, whose termini are being and non-being—and all this is evident by induction. Now art concerns itself only with things that are determinate, and there is no art to deal with the infinite.

648. Then at (476) he explains his statement that motion can be in the intermediates. And he says that an intermediate may be a starting point of change and go to either of two contraries, inasmuch as we can take the intermediate as being contrary to both extremes. For the intermediate, inasmuch as it is akin to both extremes is in a sense either of them. Hence, we speak of the intermediate as in a sense contrary relatively to the extremes and of either extreme as a contrary relatively to the intermediate; for instance, the central note is low relatively to the highest and high relatively to the lowest, and grey is light relatively to black and dark relatively to white.