LECTURE 8 (229 a 7-b 22)

THE CONTRARIETY OF MOTIONS

             715. After the Philosopher has treated the unity and diversity of motion, he here treats the contrariety of motions. This latter is a species of diversity, as is clear in Metaphysics, X.

             This discussion is divided into two parts. First he explains how one must understand contrariety in both motion and rest. Secondly, where he says, 'Again, a further difficulty . . .' (230 a 19), he raises certain difficulties about this contrariety.

             Concerning the first part he makes two points. First he treats the contrariety of motion, and secondly, the contrariety of rest, where he says, 'But since a motion appears . . .' (229 b 23).

             Concerning the first part he makes three points. First he distinguishes the different modes in which there would seem to be contrariety in motion. Secondly, where he says, 'Now motions respectively . . .' (229 a 16), he eliminates certain of these modes. Thirdly, where he says, 'Since then change differs . . .' (229 a 30), he establishes the true mode of contrariety in motion and mutation.

             716. He says, therefore, first that we must next determine which motions are contraries. Likewise, the contrariety of rest to motion, and of rest to rest, must be determined.

             But in order to treat this problem, we ought first to distinguish the modes in which the nature [ratio] of contrariety in motions can be universally understood. He distinguishes five modes.

             The first is that the nature [ratio] of contrariety in motions be understood as the arrival at and the removal from the same terminus. He expresses this as follows: '. . . contrary motions are motions respectively from and to the same thing, e.g., a motion from health and a motion to health . . .' (229 a 9-10). According to this definition [ratio] generation and corruption would seem to be contraries. For generation is motion to being, and corruption is motion from being.

             In the second mode the nature [ratio] of the contrariety of motions is understood as the contrariety of the termini from which motion begins. He expresses this as follows: '. . . or motions respectively from contraries, e.g., a motion from health and a motion from disease . . .' (229 a 11-12).

             In the third mode the contrariety of motions is understood as the contrariety of the termini at which motion ends. He expresses this as follows: '. . . or motions respectively to contraries, e.g., a motion to health and a motion to disease . . .' (229 a 12).

             In the fourth mode the contrariety of motions is understood as the contrariety of the terminus from which to the terminus to which. He expresses this as follows: '. . . or motions respectively from a contrary and to the opposite contrary, e.g., a motion from health and a motion to disease . . .' (229 a 13).

             In the fifth mode the contrariety is understood in respect to both of the termini. He expresses this as follows: '. . . or motions respectively from a contrary to the opposite contrary and from the latter to the former, e.g., a motion from health to disease and a motion from disease to health . . .' (229 a 13-14).

             The contrariety of motions must be understood according to one or more of these modes. For motion is not opposed to motion in any other way [ratio].

             717. Next where he says, 'Now motions respectively . . .' (229 a 16), he eliminates two of these modes. First he eliminates the fourth mode, which was the contrariety of the terminus from which to the terminus to which. Secondly, where he says, 'Nor are motions respectively . . .' (229 a 20), he eliminates the second mode, which was the contrariety of the termini from which motion begins. Thirdly, where he says, 'Thus we are left with . . .' (229 a 27), he explains how two of the remaining modes are related to each other.

             He says, therefore, first that motion from one contrary cannot be said to be contrary to motion to the other contrary. Thus, one would be saying that motion from health is contrary to motion to sickness. One and the same thing is not contrary to itself. Motion from health is one and the same in subject as motion to sickness. But these motions differ in reason [ratio], in this sense, that to be moved from health is not the same in reason [ratio] as to be moved to sickness. For the one implies the relation of the motion to the terminus from which, and the other the relation of the same motion to the terminus to which. Therefore, the contrariety of motion must not be understood as the contrariety of one terminus to the other.

             718. Next where he says, 'Nor are motions respectively . . .' (229 a 20), he shows that the contrariety of motions must not be understood as the contrariety of the termini from which motion begins.

             He shows this with three arguments. The first is as follows.

             Two motions which tend toward the same thing are not contraries. But two motions which recede from contraries can tend toward one and the same thing. There is equal motion from contrary to contrary or to a middle (which will be discussed later). Thus from either contrary there can be motion to one middle. Therefore, motions are not contraries because of the fact that they begin to be moved from contraries.

             719. He gives the second argument where he says, '. . . but changing to a contrary . . .' (229 a 23).

             The definition [ratio] of contrariety in motion must be taken from precisely that which makes motion contrary. But the contrariety of the termini at which motion ends seems to be more of a cause of the contrariety of motions than the contrariety of the termini from which motion begins. For when one speaks of motions beginning at contrary termini, one speaks of the removal of contrariety. But when one speaks of motions arriving at contraries, one speaks of the establishment of contrariety. Therefore, the contrariety of motions is not to be understood only in respect to the terminus from which.

             720. He gives the third argument where he says, 'Moreover, each several motion . . .' (229 a 25). The argument is as follows.

             A thing receives contrariety from the same thing from which it receives its name and species. For contrariety is a difference in respect to form, as is clear in Metaphysics, X. But each motion is named and receives its species from the terminus to which rather than from the terminus from which. Thus, motion to health is called 'curing', and motion to sickness is called 'becoming sick'. This was explained above. Hence, the contrariety of motions must be taken in respect to the terminus to which rather than in respect to the terminus from which. This is the same conclusion as above.

             721. Next where he says, 'Thus we are left with . . .' (229 a 27), he concludes that, since the two modes dealing with the contrariety of the termini have been eliminated, there remain two other modes--the third and the fifth. One of these deals only with the contrariety of the termini to which, which he indicates where he says, '. . . motions respectively to contraries . . .' (229 a 27). The other deals with the contrariety of both of the termini, which he indicates where he says, '. . . motions respectively to contraries from the opposite contraries . . .' (229 a 27-28). Furthermore, the first mode did not deal with any contrariety of termini, but with the arrival at and removal from the same terminus. He concludes, finally, that perhaps these two remaining modes are the same in subject, for motions to contraries are also from contraries. But perhaps in respect to reason [ratio] they are not the same, because motion has different relations to its termini, as was said above. His example is that motion to health and motion from sickness are the same in subject, but not in reason [ratio]. It is the same with motion from health and motion to sickness.

             722. Next where he says, 'Since then change differs . . .' (229 a 30), he shows how contrariety is found in motion. He shows this first in regard to motion to a contrary. Secondly where he says, 'And wherever a pair of contraries . . .' (229 b 15), he shows this in regard to motion to a middle.

             Concerning the first part he makes two points. First he shows what causes contrariety in motions, and secondly in mutations, where he says, 'On the other hand . . .' (229 b 10).

             Concerning the first part he makes two points. First he establishes his position with a syllogism, and secondly by induction, where he says, 'Moreover, the consideration of . . .' (229 b 2).

             He first gives the following argument. The contrariety of things is established by their proper species and nature [ratio]. The proper specific nature [ratio] of motion is that it has two termini and it is a mutation from a certain affirmative subject to a certain affirmative subject. (In this way motion differs from mutation which does not always have two affirmative termini.) Hence it follows that the contrariety of motion requires contrariety in respect to both of the termini. Thus, properly speaking, motion from contrary to contrary is contrary to motion from contrary to contrary. For example, motion from health to sickness is contrary to motion from sickness to health.

             723. Next where he says, 'Moreover, the consideration of . . .' (229 b 2), he shows the same thing by induction.

             First he mentions bodily alteration. Becoming sick is contrary to becoming healthy. The former is motion from health to sickness, and the latter is motion from sickness to health. This is also clear in alterations of the soul. To be deceived, not by one's self but by another, is contrary to learning. These motions are to contraries from contraries. For learning is a motion from ignorance to knowledge, and being deceived is a motion from knowledge to ignorance.

             He explains why he adds 'not by one's self'. It sometimes happens that one acquires knowledge by one's self. This is called discovery. And sometimes one acquires knowledge, not by one's self, but from another. This is called learning. In the same way it sometimes happens that one is deceived by one's self, and sometimes by another. This latter is properly opposed to learning.

             Such contrariety is also apparent in local motion. Upward motion is contrary to downward motion. These are contraries in respect to length. Motion to the right is contrary to motion to the left. These are contraries in respect to width. Forward motion is contrary to backward motion. These are contraries in respect to depth.

             But it must be realized that he is speaking here of these differences of position, that is, length, width, and depth, insofar as they are in man. For upward and downward are considered in respect to the length of man; right and left in respect to his width, and forward and backward in respect to his thickness, which is called depth.

             It must also be realized that contrariety in respect to upward and downward is also found in natural motions. But contrariety in motions in respect to right and left, and forward and backward, is not found in nature but in motion from the soul, which moves to these contrary parts.

             724. Next where he says, 'On the other hand . . .' (229 b 10), he shows how there is contrariety in mutations.

             First he shows how contrariety of mutation is found in things in which there is contrariety. Secondly, where he says, 'And in all cases . . .' (229 b 12), he shows how this is found in things in which there is no contrariety.

             He says, therefore, first that if there is contrariety only in respect to the terminus to which (as when that which is to a contrary is called contrary), this does not produce contrariety of motion, but of mutation, which is generation and corruption. Thus, to become white and to become black are contraries. And it is not necessary that the contrariety of these generations include a contrariety of the terminus from which. For in generation the terminus from which is not affirmative but negative. White comes to be from non-white, but not from something affirmative. For change from subject to subject is not mutation, but motion.

             725. Next where he says, 'And in all cases . . .' (229 b 12), he shows that in things in which there is no contrariety, such as substances and such things, the contrariety of mutation is due to the arrival at and removal from the same terminus. He says that in things in which there is no contrary, the contrariety of mutation is due to a removal from and an arrival at the same thing. For example, the arrival at the form of fire, which pertains to the generation of fire, and the removal from this same form, which pertains to the corruption of fire, are contraries. Hence, generation is contrary to corruption, and each removal is contrary to each arrival. However, such things are not motions, but mutations.

             It is clear, therefore, that of the five modes given above, two of them, the second and the fourth, have no application. But one of them applies to the contrariety of motions, and two apply to the contrariety of mutations.

             726. Next where he says, 'And wherever a pair of contraries . . .' (229 b 15), he treats the contrariety of motion in respect to a middle.

             He says that, whenever a middle is found between contraries, motions which terminate at this middle must be said to be contraries in the same way that motions which terminate at contraries are contraries. For a motion uses a middle as a contrary, so that from this middle there can be motion to either contrary. For example, from grey, which is a middle between black and white, a thing is changed to white as if it were changed from black to white. And conversely, a thing is changed from white to grey as if it were changed to black. And a thing is changed from black to grey as if it were changed to white. For since grey is a middle between both of these extremes, it is said to be either of them. In comparison to white it is black, and in comparison to black it is white, as was said above.

             Finally he draws his main conclusion. Motion is contrary to motion in respect to the contrariety of both of the extremes.