Commentary Aristotle Physics
Book 5. Division of Motion into Its Species
Lecture 1. Motion per se is distinguished from motion per accidens
Everything that changes does so in one of three senses.
It may change accidentally, such as when we say that something musical walks, that which walks being something in which aptitude for music is an accident.
Again, a thing is said without qualification to change because something belonging to it changes, that is, in statements that refer to part of the thing in question. Thus, the body is restored to health because the eye or the chest—that is, to say a part of the whole body—is restored to health.
And above all, there is the case of a thing that is in motion neither accidentally nor in respect of something else belonging to it, but in virtue of being itself directly in motion.
Here we have a thing that is per se movable; and it is a different thing according to the kind of motion—for instance, it may be alterable, and within the sphere of alteration, it is different according as it is curable or able to be heated.
And there are the same distinctions in the case of the mover: one thing causes motion accidentally, another partially (because something belonging to it causes motion), another of itself directly, such as the physician healing and the hand striking.
We have, then, the following: that which directly causes motion, that which is in motion, and that in which motion takes place, time; and (besides these) we have that from which and that to which it proceeds, for every motion proceeds from something and to something, that which is directly in motion being distinct from that to which it is in motion and that from which it is in motion.
For instance, we may take the three things “wood,” “hot,” and “cold,” of which the first is that which is in motion, the second is that to which the motion proceeds, and the third is that from which it proceeds.
This being so, it is clear that the motion is in the wood, not in its form, for the motion is neither caused nor experienced by the form or the place or the quantity. So, we are left with a mover, a moved, and a goal of motion.
I do not include the starting point of motion, since it is the goal rather than the starting point of motion that gives its name to a particular process of change.
Thus, “corruption” is change to non-being, though it is also true that what perishes changes from being, and “generation” is change to being, though it is also change from non-being.
Now, a definition of motion has been given above, from which it will be seen that every goal of motion, whether it be a form, a passion, or a place, is immovable—as, for instance, knowledge and heat.
Here, however, a difficulty may be raised. Passions, it may be said, are motions, and whiteness is a passion.
Thus, there may be change to a motion. To this, we may reply that perhaps it is not whiteness that is a motion, but whitening.
Here also, the same distinctions are to be observed: a goal of motion may be so accidentally, or partially and with reference to something other than itself, or directly and with no reference to anything else.
For instance, a thing that is becoming white changes accidentally to an object of thought, the color being only accidentally the object of thought; it changes to color, because white is a part of color, or to Europe, because Athens is a part of Europe; but it changes essentially to white color.
It is now clear in what sense a thing is in motion essentially, accidentally, or in respect of something other than itself, and in what sense the phrase “directly and per se” is used in the case both of the mover and of the moved, and it is also clear that the motion is not in the form, but in that which is in motion, that is to say “the actually mobile.”
Now, accidental change we may leave out of account, since it is to be found in everything, at any time, and in any respect.
Change that is not accidental, on the other hand, is not to be found in everything, but in contraries and in things intermediate between contraries, and in contradictories, as may be proved by induction.
An intermediate may be a starting point of change, since, for the purposes of the change, it serves as contrary to either of two contraries, for the intermediate is in a sense the extremes.
Hence we speak of the intermediate as in a sense a contrary relative to the extremes and of either extreme as a contrary relative to the intermediate: for instance, the central note is low relative to the highest and high relative to the lowest, and grey is light relative to black and dark relative to white.
638. After discussing motion and the things that accompany motion in general, the Philosopher now undertakes giving 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 6, at “now, if the terms” (231a21; [750]).
The first is divided into two parts:
first, he divides motion into its species;
second, he discusses unity and opposition of motion, at “let us now proceed” (226b18; [684]).
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 “and, since every change” (224b35; [649]).
The first is divided into two parts:
in the first, he distinguishes per se motion from per accidens;
in the second, he shows that, while per accidens need not be discussed, per se motion must be, at “now, accidental change” (224b26; [647]).
In regard to the first, he does two things:
first, he distinguishes per se from per accidens motion;
second, he makes a summary, at “it is now clear” (224b22; [646]).
In the first part, he distinguishes per se motion from per accidens motion in three ways:
first, on the side of the mobile;
second, on the side of the mover, at “and there are the same” (224a30; [640]);
third, on the side of the terminus of motion, at “we have, then, the following” (224a34; [641]).
639. He first says, therefore (224a21), that whatever changes, that is, whatever is being changed, is described as doing so in three ways.
The first is per accidens, as when we say that a musician is walking because the person who is walking happens to be a musician.
Second, a thing is described as being changed without qualification even though only some part of it is changing, that is, in statements that 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, is restored to health.
Third, something is said to be 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 varies according to the various kinds of motion: 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 healable if it is moved in respect of health, and heatable if it is moved in respect of heat.
640. Then, at “and there are the same” (224a30), from the side of the mover, he distinguishes per se from per accidens motion. And he says that the preceding distinctions that 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;
second, by reason of a part (when some part of the mover causes motion), as the man is said to strike because his hand strikes;
in a third way, as acting or moving directly and per se, as the healer heals.
641. Then, at “we have, then, the following” (224a34), looking at the terminus of motion, he divides motion once more in the same manner.
First, he sets out some presuppositions;
second, he gives his division, at “here also, the same distinctions” (224b16; [646]).
About the first, he does three things:
first, he declares how many things are required for motion;
second, he compares them to one another, at “that which is directly” (224b1; [642]);
third, he settles a question, at “now, a definition of motion” (224b10; [644]).
He says therefore (224a34) that five things are needed for motion.
First, there must be a first mover, that is, a source from which the motion originates;
second, a mobile that is being moved;
and third, 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 “that which is directly” (224b1), he compares these five things:
first, he compares the mobile to the two termini;
second, he compares one terminus with the other, at “I do not include” (224b7; [643]).
He says therefore (224b1) 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 1.
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, that is, 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 form, that is, a quality, as in alteration; a place, as in local motion; or a quantity, as in the motion called growing and decreasing. However, the mover moves the subject, which is being moved, into a goal of motion, that is, the terminus to which. Therefore, since motion exists in the subject being moved but not in the terminus, it is clear that the mobile subject is distinct from the terminus of the motion.
643. Then, at “I do not include” (224b7), he compares one terminus with the other. And he says that a change gets its name from the terminus to which, rather than from the terminus from which; 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 from which is taken away but a terminus to which is acquired, and for this reason, motion seems to have a repugnance for the terminus from which and a kinship to the terminus to which—that is why it gets its name from the latter.
644. Then, at “now, a definition of motion” (224b10), he settles a doubt.
And about this, he does three things.
First, he mentions two things that are clear from the foregoing:
first, that we have already pointed out in book 3 what motion is;
second, that, in the immediately foregoing, we have said that forms—that is, qualities—and place and passions, which are the termini of motion, are not themselves being changed, since there is no motion existing in them, as we have already said; as is clear from heat, which is a certain species, and from science, which is a certain passion or passible quality.
Second, at “here, however, a difficulty” (224b13), he mentions a matter about which there is doubt, saying that someone may wonder whether passions, such as heat and coldness and whiteness and blackness, might not be types of motion, since none of them is a subject of motion.
Third, at “thus, there may be” (224b14), he mentions a discrepancy that would arise if such a view were posited. Since whiteness is a terminus into which a motion tends, if whiteness itself were a motion, it would follow that motion is 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 that is motion, but whitening. But he adds perhaps because he has not yet proved that a motion cannot terminate in a motion.
645. Then, at “here also, the same distinctions” (224b16), 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 division, which is one taken on the side of the terminus.
And, since motions are named from the terminus to which rather than from the terminus from which, he develops his division not on the side of the latter, but of the former. And he says that, even here—that is, the termini—it is possible to find in motion a goal that is so per accidens, and one that is so according to a part or to something other than itself, and one that is directly and not with reference to something else.
It is 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, since it is said to be changing into a color because it is becoming white, which is a part of the genus color.
And, similarly, if I should say of someone who is going to Athens that he is going to Europe, this will be according to a part, 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 “it is now clear” (224b22), he summarizes what he has said. And he says that it is clear how something is in motion per se, how it is so per accidens, and how in respect of something other than itself, that is, 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 form, that is, the quality that is the terminus of motion; rather, motion is in what is being moved, that is, in the actually mobile, which is the same thing.
647. Then, at “now, accidental change” (224b26), he shows which kind of motion needs to be discussed.
First, he states his proposition;
second, he explains something he said, at “an intermediate may be” (224b30; [648]).
He says first, therefore, 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, since 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 contraries and in things intermediate between contraries in respect to motions that affect quantity, quality, and place, and in contradictories, such as 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 “an intermediate may be” (224b30), 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 relative to the extremes and of either extreme as a contrary relative to the intermediate; for instance, the central note is low relative to the highest and high relative to the lowest, and grey is light relative to black and dark relative to white.