Seite - 187 - in The Priority of Locomotion in Aristotle’s Physics

this [kind of] change would also have primacy over the other [kinds] in essence, because of this and [1] for the reason that what is undergoing a change of the [different] changes departs from its essence least in under- going locomotion; [2] for it [i.e. locomotion] alone does not change any- thing of the being [of that which undergoes the change], as of what alters the quality [changes], and of what grows and diminishes the quantity. The second argument presents another reason for locomotion’s primacy in essence. The claim is that locomotion is prior in this sense, since of the four kinds of change it is the only one which completely preserves the essence of its subject. I will argue that Aristotle uses this claim to show in this second sub-argument that locomotion is also prior in essence with respect to eter- nal things, after having argued that locomotion is prior in this way in per- ishable things. If successful, he will have made clear that locomotion in this sense is primary in essence in all things that have locomotion. According to this argument, locomotion has primacy over the other kinds of change, since, as sentence (1) states, if something x is undergoing a change in place, x somehow departs less from its essence (οὐσία) than if it is undergoing any of the other kinds change. The reason (γάρ) for this claim is presented in sentence (2). It does not appear to add very much to the claim already stated: x’s being (εἶναι) does not change at all when x undergoes a locomotion, while its being changes when x is subject to altera- tion, growth or diminution, for x then changes in quality or quantity. Aris- totle does not present any further explanation for these claims, although they are far from self-evident and, as I will show, seem to contradict a basic Aristotelian assumption of his theory of change: change in quality and in quantity—along with locomotion—are labelled as non-substantial changes by Aristotle, i.e. as changes that by definition do not change their subject’s essence.48 This seems to be in conflict with what is stated in sentence (1); for in what way can the non-substantial kinds of change be the cause for their subject’s ‘departing’ from or ‘stepping out’ of its essence (τῆς οὐσίας ἐξίσταται), i.e. its change in essence at all? And, more importantly, if they do not cause a change in essence in general, how could they be responsible for different degrees of change in essence—as suggested in sentence (1)? And assuming that these points turn out to be unproblematic, in what way would this argument fit into the greater context of the inquiry for the pri- mary kind of change? In order to solve these problems and to explain how the argument shows what it is supposed to show, it is necessary to look at it in more detail. I will proceed as follows: I will start by examining the claim stated in sentence (2), namely, that, if x undergoes locomotion, x’s being does not change at 48 See for instance Phys. V 1, 225a34–b5. Locomotion alone preserves its subject’s essence 187 ISBN Print: 9783525253069 — ISBN E-Book: 9783647253060 © 2014, Vandenhoeck & Ruprecht GmbH & Co. KG, Göttingen