Page - 68 - in The Priority of Locomotion in Aristotle’s Physics

most important way in which locomotion is prior, according to the argu- ment. For what Aristotle seems to emphasise in particular is that without alteration there is no change in magnitude and without locomotion, again, alteration cannot come about.77 This stresses the fact that the occurrence of locomotion is a necessary requirement for either of the other two kinds of change in living beings, i.e. they cannot occur without it. In this way the sense of priority shown here seems to be one that is also discussed in the third argument for the priority of locomotion and which I will call ontologi- cal priority in this context.78 Something x is ontologically prior to y, if and only if for y to be there must be x, but not vice versa.79 In other words, y cannot be without x, while x can be without y. This kind of relation between x and y might be described as an asymmetric relation of ontological dependency. This fits very well with what I just said: locomotion has ontolo- gical priority over change in quality and quantity, since the latter two can- not exist without the former. Yet, although Aristotle has clearly shown this, and in which sense this is the case, he has not said anything explicitly about the fact that locomotion does not presuppose the occurrence of any of the other kinds of change.80 But this is not entirely clear, because it seems there are cases that show that locomotion also depends on the occurrence of some other kind of change. For instance, one might say that it is necessary that I eat food and digest it in order to be able to walk around. For, if I do not eat I will at some point become too weak to walk around. As Aristotle has shown, the digestion of food necessarily involves an alteration, so that it seems that locomotion in this sense cannot occur without it. Moreover, something similar seems to hold true with respect to growth: the fact that living things need to develop muscles and limbs, i.e. need to grow in order to be able to move at all, also seems to suggest that locomotion depends on this other kind of non-sub- 77 ἀλλοιώσεως μὴ προϋπαρχούσης: “without a preceding alteration” (260a29–30) and ἄνευ φορᾶς: “without locomotion” (260b4). 78 See Phys. VIII 7, 260b17–19. For my discussion of the third argument see chapter 5, for Aristotle’s explanation of this way of priority in Phys. VIII 7 see section 5.4.1. 79 Also Simplicius expresses this view in In Phys. 8, 1265, 16–20, where he states that in this argument Aristotle is showing that locomotion is πρωτὴ κατὰ φύσιν. This does not refer to the kind of priority for which the fifth argument (261a13–23) according to Aristotle explicitly argues, namely for priority in nature (τῇ φύσει πρότερον) and in essence (κατ᾽ οὐσίαν), but to what I just called ontological priority and which Aristotle calls prior in nature (and in essence) and assigns it to Plato in Met. V 11, 1019a1–4, namely the one according to which x is prior to y, if and only if x can exist without y, but not vice versa. This is also the kind which is presented in Cat. 12, 14a29–35, as the second kind of priority. 80 Simplicius, In Phys. 8, 1265, 17–19, clearly thinks that Aristotle shows in the argument that locomotion does not depend on the occurrence of other kinds of change, however, he does not explain how exactly this is supposed to follow from what is said by Aristotle. 68 Change in quality and quantity of living beings ISBN Print: 9783525253069 — ISBN E-Book: 9783647253060 © 2014, Vandenhoeck & Ruprecht GmbH & Co. KG, Göttingen