LECTURE 2 (224 b 35-225 b 4)

THE SPECIES OF MUTATION ARE ESTABLISHED. IT IS SHOWN WHICH OF THESE SPECIES IS MOTION IN THE STRICT SENSE

             649. After the Philosopher has distinguished motion per se from motion per accidens, he here divides mutation and motion per se into their species.

             It must be realized here that, when Aristotle defined motion above in Book III, he took the word 'motion' as common to all the species of mutation. Here he attributes this meaning to the word 'mutation'. And he uses 'motion' in a more limited sense as a certain species of mutation.

             Therefore this part is divided into two parts. In the first part he divides mutation into its species, one of which is motion. In the second part he subdivides motion into its species, where he says, 'If, then, the categories . . .' (225 b 5).

             Concerning the first part he makes two points. First he gives the division of mutation. Secondly, where he says, 'Now change from non-subject . . .' (225 a 12), he clarifies the parts of this division.

             Concerning the first part he makes three points. First he sets forth certain things which are necessary for the division of mutation. Secondly, where he says, 'So it follows necessarily . . .' (225 a 7), he concludes from this the division of mutation. Thirdly, where he says, '. . . for the fourth . . .' (225 a 10), he refutes a certain objection.

             650. He says, therefore, first that every mutation is from something to something. This is clear from the very word 'mutation' which denotes that something is after another, and that one thing is prior and another posterior. Hence on these suppositions it is necessary that that which is changed be changed in four ways. For either both termini are affirmative, and thus a thing is said to be changed from subject to subject. Or the terminus from which is affirmative and the terminus to which is negative, and thus a thing is said to be moved from subject to non-subject. Or, conversely, the terminus from which is negative and the terminus to which is affirmative, and thus a thing is said to be moved from non-subject to subject. Or both termini are negative, and thus a thing is said to be changed from non-subject to non-subject. The word 'subject' here does not mean that which sustains form, but rather anything which is affirmatively signified.

             651. Next where he says, 'So it follows necessarily . . .' (225 a 7), he concludes from the above the division of mutation. He says that it necessarily follows from the above that there are three species of mutation. One species is from subject to subject, as when a thing is changed from white to black. Another is from subject to non-subject, as when a thing is changed from being to non-being. The third species, on the other hand, is from non-subject to subject, as when a thing is changed from non-being to being.

             652. Next where he says, '. . . for the fourth . . .' (225 a 10), he refutes a certain objection. For one might object that, since he has stated that a thing is changed in four ways, he ought to conclude that there are four species of mutation, and not just three.

             But he refutes this objection by saying that there cannot be a species of mutation from non-subject to non-subject. For every mutation is between opposites. But two negations are not opposites, for it cannot be said that they are either contraries or contradictories. A sign of this is that negations are simultaneously true of one and the same thing. Thus a stone is neither healthy nor sick. Hence since mutation per se occurs only between contraries and between contradictories, as was said above, it follows that there is no mutation per se from negation to negation, but only mutation per accidens. For when a thing is changed from white to black, it is changed per accidens from non-black to nonwhite. In this way a thing is said to be changed from non-subject to non-subject. Moreover, that which is in a genus per accidens cannot be a species of that genus. Therefore, there cannot be a species of mutation from non-subject to non-subject.

             653. Next where he says, 'Now change from non-subject . . .' (225 a 12), he clarifies the parts of the given division.

             Concerning this he makes three points. First he clarifies two parts of the division. Secondly, where he says, 'Now the expression . . .' (225 a 20), he shows that neither of these is motion. Thirdly, where he says, 'Since, then, every motion . . .' (225 a 34), he concludes that the remaining part of the division is motion.

             Concerning the first part he makes two points. First he clarifies one part of the division, and secondly the other, where he says, 'Change from subject . . .' (225 a 17).

             654. He says, therefore, first that mutation from non-subject to subject is between opposites which are contradictories. This is called generation, which is a mutation from non-being to being.

             But generation is twofold. For there is simple generation in which a thing is generated simply, and there is another generation in which a thing is generated accidentally. He gives an example of each generation. The first example is of the second type of generation. He says that, when a thing is changed from non-white to white, there is a generation of 'this' and not a simple generation. The second example is of the first type of generation. He says that generation from simple non-being to being which is substance is simple generation. According to this we say simply that a thing comes to be and does not come to be. For since generation is mutation from non-being to being, a thing is said to be generated in this way when it is changed from non-being to being.

             But when a thing comes to be white from non-white, it is not changed from non-being simply to being simply. For that which is properly changed is the subject, and the subject of white is some being in act. Hence, since the subject remains throughout the whole mutation, at the beginning of the mutation it was also being in act, that is, white. Therefore, this is not called becoming simply, but becoming this, that is, white.

             But the subject of substance is not being in act, but being in potency only, that is, primary matter, which at the beginning of generation is under privation and at the end is under form. Therefore a thing becomes simply in respect to the generation of substance.

             From this it can be seen that, in respect to a form which presupposes another form in matter, there is no simple generation but only accidental generation. For any form puts a being in act.

             655. Next where he says, 'Change from subject . . .' (225 a 17), he clarifies the other part of the division.

             He says that mutation from subject to non-subject is called corruption. But there is simple corruption, which is from substantial being to non-being; and there is another corruption to the opposite negation of any affirmation, as from white to non-white. This latter is a corruption of 'this', as was also said in regard to generation.

             656. Next where he says, 'Now the expression . . .' (225 a 20), he shows that neither of the foregoing is motion.

             First he shows that generation is not motion, and secondly that corruption is not motion, where he says, 'So, too, "perishing" . . .' (225 a 33).

             He proves the first point with two arguments. The first is as follows. That which is simply not a 'this' cannot be moved. For that which is not is not moved. But that which is generated simply is not a 'this'; for it is simply non-being. Therefore, that which is generated simply is not moved. Therefore simple generation is not motion.

             To clarify the first proposition he says that non-being is said in three ways. In regard to two of these ways non-being is not moved. In regard to the third way it is moved per accidens.

             In one way being and non-being are said in respect to the composition and division of the proposition, such that they are the same as the true and the false. Such being and non-being are in the mind only, as is said in Metaphysics, VI. Hence motion does not pertain to them.

             In another way non-being is said to be that which is in potency, insofar as being in potency is opposed to that which is being in act simply. And such non-being is also not moved.

             In a third way non-being is said to be that which is in potency and which does not exclude being in act simply, but only being in this act. Thus non-white and non-good are called non-being. Such non-being can be moved per accidens insofar as such non-being occurs in something existing in act which happens to be moved.

             Now since it is impossible for that which is not to be moved, it is clear that that which is simply not a 'this' is in no way moved, neither per se nor per accidens. Hence generation cannot be motion. For that which is not becomes or is generated. And although, as was said in Book I, a thing comes to be from non-being per accidens and from being in potency per se, nevertheless it is true to say that that which becomes simply simply is not. Hence it cannot be moved; and for the same reason [ratio] it is not at rest. Thus generation is neither motion nor rest.

             Therefore, if one holds that generation is motion, these difficulties follow: non-being is moved and is at rest.

             657. He gives the second argument where he says, '. . . and it may be further . . .' (225 a 31). The argument is as follows.

             Whatever is moved is in place. But that which is not is not in place, because it can be said to be anywhere. Therefore that which is not is not moved. This is the same conclusion as the above. The truth of the first proposition arises from the fact that, since local motion is the first motion, it is necessary that whatever is moved be moved with respect to place, and thus is in place. And when that which is prior is removed, things which are consequent are also removed.

             658. Next where he says, 'So, too, "perishing" . . .' (225 a 33), he proves that corruption is not motion. Nothing is contrary to motion except motion or rest. But generation, which is neither motion nor rest, as was shown, is contrary to corruption. Therefore corruption is not motion.

             659. Next where he says, 'Since, then, every motion . . .' (225 a 34), he concludes from the above that motion is the remaining part of the division given above.

             Motion is a certain species of mutation because in motion there is something after another, which he said above pertains to the nature [ratio] of mutation. But motion is neither generation nor corruption, which are mutations in respect to contradictories. And since there are only three species of mutation, it follows of necessity that motion is mutation from subject to subject.

             Moreover by the two 'subjects', that is, the two affirmations, we mean contraries or intermediaries. For privation also in a way is a contrary and is sometimes signified affirmatively. Thus naked is a privation, and white and black are contraries.