LECTURE 14 (260 a 20-261 a 27)

LOCAL MOTION IS THE FIRST MOTION

1086. After the Philosopher has shown that the first mover is immobile and the first motion is eternal, he begins here to show what the first motion is and what the nature of the first mover is.

             This discussion is divided into two parts. First he shows what the first motion is. Secondly, where he says, 'We have now to assert . . .' (266 a 10), he shows what the nature of the first mover is.

             Concerning the first part he makes two points. First he states his intention. Secondly, where he says, 'Now of the three . . .' (260 a 27), he develops his position.

             He says, therefore, first that in order that the foregoing may be more certain it is necessary to make a new beginning and to consider whether there is some motion which happens to be infinitely continuous, and if there is such a motion, what is it and is it the first motion.

             But someone might think that the first motion is not a motion which is continuous. To reject this he adds that since motion must be eternal, and since the first motion is eternally continuous because it is caused by a first immobile mover, it is clearly necessary that that motion which is eternally continuous must be the same as the first motion.

             1087. Next where he says, 'Now of the three . . .' (260 a 27), he proves his position, first by means of arguments, and secondly by means of the statements of the ancients, where he says, 'As to locomotion being the primary . . .' (265 b 16).

             Concerning the first part he makes two points. First he shows that local motion is first. Secondly, where he says, 'We have now to show . . .' (261 a 28), he shows which local motion is first.

             He establishes the first point in three ways; first by means of the properties of motions; secondly, by means of the distinction of prior and posterior, where he says, 'Again, there is another . . .' (260 b 15); and thirdly, by means of the order of mobile objects, where he says, 'Above all it is plain . . .' (261 a 24).

             1088. In regard to the first part he gives two proofs, the first of which proceeds as follows.

             First he states his intention. He says that there are three species of motion; one with respect to quantity, which is called the motion of increase and decrease; another with respect to passive quality, which is called alteration; and the third with respect to place, which is called local motion. Of these three local motion must be first.

             Secondly he proves this as follows. It is impossible for increase to be the first motion.

             For increase cannot exist unless alteration pre-exists. For that by which a thing is increased is in a way similar and in a way dissimilar. It is clear that it is dissimilar, for that by which a thing is increased is nourishment, which in the beginning is contrary to that which is nourished because of its different disposition. But when it is added such that it causes an increase, it must be similar. Only through alteration does a thing pass from dissimilarity to similarity. Therefore, before an increase there must exist an alteration through which nourishment is changed from one contrary disposition to another.

             Thirdly he shows that local motion precedes every alteration. For if a thing is altered, there must be an alterer which makes that which is potentially hot to be actually hot. If, however, this alterer were always at the same distance from that which is altered, it would not make it hot now rather than before. It is clear, therefore, that in alteration the mover does not remain at the same distance from that which is altered. Rather at one time it is nearer, and at another it is further away. This cannot occur without local motion. Therefore, if motion must be eternal, then local motion must be eternal since it is the first of motions. And if among local motions one is prior to the others, and if the foregoing is true, then the first local motion must be eternal.

             1089. He gives the second argument where he says, 'Again, all affections . . .' (260 b 9). The argument is as follows.

             As was established in Book VII, alterations occur with respect to passions or passive qualities. According to the opinion of the ancients, the first of these seems to be density and rarity, since both heavy and light, and soft and hard, and warm and cold seem to follow from rarity and density and to be distinguished with respect to them (for among the elements, heavy and cold are found to be dense, and warm and light are found to be rare). And this is in a way true, if the order of the passions is based on their nearness to the material principle. For the rare and the dense especially seem to pertain to matter, as is clear from what was said in Book IV. Moreover, density and rarity seem to be a kind of union and separation. And it was precisely in virtue of this union and separation that the ancient philosophers held that the generation and corruption of substances occur. He now uses this opinion as probable before he establishes the truth about generation and corruption in De Generatione. Things which are united and separated seem from this very fact to be changed with respect to place. Hence, local motion is the principle of alteration.

             It should be noted that the union and separation of actually existing bodies pertains to local motion. But the union and separation with respect to which the same matter is contained under large or small dimensions does not pertain to local motion, but to the motion of alteration. And it is in respect to this that in Book IV Aristotle established the nature [ratio] of the rare and the dense. But here he is speaking of what is probable according to the opinion of other philosophers.

             Moreover, just as local motion is required for alteration, so also is it required for increase. The magnitude of that which is increased or decreased must be changed with respect to place. For that which is increased expands into a larger place, and that which is decreased is contracted into a smaller one. Therefore, it is clear that local motion is naturally prior to both alteration and increase.

             1090. Next where he says, 'Again there is another . . .' (260 b 15), he proves the same thing by distinguishing the modes of the prior and the posterior.

             He says that it will be clear from this consideration that local motion is the first among motions. For just as in other cases a thing is said to be prior to another in many ways, this is also true of motion.

             In one way a thing is said to be prior such that if it does not exist, the others will not exist, yet it can exist without the others. For example, one is prior to two, since two cannot be unless one is, but one can be if two do not exist. Secondly, a thing is said to be prior in time, for example, that which is further removed in the past from the present now, or nearer in the future, as was said in Book IV. Thirdly, a thing is said to be prior with respect to substance, that is, with respect to the completion of substance, as act is prior to potency and the perfect to the imperfect.

             1091. Secondly, where he says, 'Now there must be motion . . .' (260 b 20), he proves that local motion is first in the three ways mentioned above. First he discusses the first way; secondly, the second way, where he says, 'Secondly, locomotion . . .' (260 b 29); and thirdly, the third way, where he says, 'Thirdly, that which is . . .' (261 a 13).

             He says, therefore, first that since motion must be eternal, as was proven above, this may be understood in two ways. First there may be some continuous motion; secondly, it may be that motions are consecutively related such that between them there is no intermediate. The eternity of motion is better preserved, however, if motion is continuous. Furthermore, it is more fitting for it to be continuous rather than consecutive because it would then have more of the nature [ratio] of unity and eternity. We ought always to accept what is more fitting in nature, if it is possible. It is possible, moreover, for motion to be infinitely continuous, but this is true only of local motion. This at present we assume; it will be proven later. From this it appears to be necessary to admit that local motion is first.

             For the other motions are not required for local motion. It is not necessary that what is changed with respect to place be either increased or altered, for it is not necessary that a body which is moved with respect to place be generated or corrupted. But increase and alteration have place only in those things which are generated and corrupted. But none of these motions occurs unless there is that eternal motion which the first mover moves, and which we said could only be local motion. Therefore, local motion can occur without the others, but not vice versa. Hence local motion is first according to the first mode of priority.

             1092. Next where he says, 'Secondly, locomotion . . .' (260 b 29), he proves that it is prior in time.

             Concerning this he makes two points. First he shows that, simply speaking, it is prior in time. For that which is eternal, simply speaking, is prior in time to that which is not eternal. Only local motion, however, happens to be eternal, as has been said. Hence, simply speaking, it is first in time.

             1093. Secondly, where he says, 'It is true indeed that . . .' (260 b 30), he rejects a certain objection which seems to contradict this. If we consider a newly-generated body, local motion is the last in time among all its motions. For it is first generated, afterwards it is altered and increased, and finally it has motion with respect to place when it has been perfected, as is clear in man and in many animals.

             But this does not disprove that local motion is absolutely first in time. For before all the motions which occur in that which is generated, some local motion must have preceded in some prior mobile object which is the cause of generation in things which are generated, just as the generator is the cause of that which is generated even though it itself is not generated.

             And he shows that the motion preceding generation is local motion and that it is absolutely the first of motions. He says that generation seems to be the first motion in things which are generated because a thing must come to be before it is moved. And this is true of whatever is generated. Nevertheless there must be some moved thing prior to things which are generated, which itself has not been generated. Or, if it has been generated, there must be another prior to it. Hence, either there must be an infinite series, which is impossible, as was shown above, or there must be a first.

             But it is impossible for generation to be first. For then it would follow that all things which are moved are corruptible, for whatever is generable is corruptible. Hence, if the first mobile object is generated, it follows that it is corruptible, and consequently so are all other mobile objects. And if generation is not absolutely first, it is clear that none of the consequent motions can be absolutely first. By 'consequent motions' I mean increase, alteration, decrease, and finally, corruption, all of which motions follow generation in time. Hence, if generation is not prior to local motion, it follows that none of the other mutations can be absolutely prior to local motion. And so, since there must be something which is absolutely first, it follows that local motion is first.

             1094. Next where he says, 'Thirdly, that which is . . .' (261 a 13), he proves that local motion is first in perfection. He proves this in two ways.

             The first is as follows. Everything which comes to be, while it is becoming, is imperfect and tends toward its principle, that is, it tends to become like the principle of its own origin, which is naturally first. From this it is clear that that which is posterior in generation is prior with respect to nature. But in the process of generation in all generable things local motion is found to be last, not only in the same thing, but also in the total progress of the nature of generable things. Among these, certain living things are totally immobile with respect to place because they lack organs, for example, plants, which do not have the organs of progressive motion, and likewise many genera of animals. But local motion is present in perfect animals. Therefore, if local motion is present in things which better embrace nature, that is, which achieve a more perfect nature, it follows that local motion is first of all motions with respect to the perfection of substance.

             1095. Secondly, where he says, '. . . but also because a thing . . .' (261 a 21), he shows the same thing as follows.

             Insofar as a motion removes less from a mobile object, its subject is to that extent more perfect, and even the motion itself is in a way more perfect. But only in local motion is there nothing removed from the mobile object. For in alteration there is a mutation with respect to quality, and in increase and decrease there is a mutation with respect to quantity, which are in the subject. The mutation of generation and corruption occurs with respect to the form which determines the substance of the object. Local motion occurs only with respect to place, which it contains externally. Hence it follows that local motion is the most perfect.

             1096. Next where he says, 'Above all it is plain . . .' (261 a 24), he proves by means of the mobile object that local motion is first.

             It is clear that a self-mover most properly moves itself with respect to local motion. Since, therefore, a self-mover is the principle of other movers and mobile objects, and consequently is first among all things which are moved, it follows that local motion, which is proper to it, is first among all motions.

             Therefore, he concludes from the foregoing that local motion is the first among all motions.