Page - 209 - in The Priority of Locomotion in Aristotle’s Physics

here as well it helps to have in mind the context in which the argument is stated: Aristotle is trying to demonstrate that locomotion is prior in differ- ent respects to the other kind of change in order to show that only locomo- tion can be the kind of change that is directly caused by the first unmoved mover. But in what way does what we have learned about locomotion in the second argument contribute anything to this project? The solution may be found if we think about what is directly caused to change by the first unmoved mover, that is, the outermost heavenly sphere. According to Aristotle the spheres and the stars as part of the superlunary realm are not subject to substantial change, but are eternal. This, I take it, is what connects the fact that locomotion does not change its subject’s essence to the greater project of showing that the kind of change that is directly and primarily caused by the first unmoved mover and undergone by the outer- most sphere can only be locomotion. The way in which locomotion is prior in essence to the other kinds of change is with respect to the primum mobile and to eternal things: the outermost sphere can only undergo a change that leaves its essence completely untouched and which is of such a nature that it can be engaged in eternally without thereby posing any threat to its essence. As I have shown in my discussion of the second sub-argument for priority in essence, the only change which does this in the full sense is change in place. For, in contrast to change in quality and quantity, it does not affect its subject’s being in any way and therefore not even in principle can it entail any substantial change; and that coming to be and corruption are not appropriate candidates has been clear from the beginning and did not need an extra argument. The following then is the way in which locomotion is prior in essence with respect to the outermost sphere and to eternal things, respectively: locomotion belongs more to what the outermost sphere is, i.e. to its essence, in the sense that locomotion so to speak is more specific to it than any of the other kinds of change that one might have thought to belong to this or any other eternal entity. For, again, locomotion does not change its subject’s being and essence in any way and this is the reason why the only change the eternal sphere of the stars (as well as all other heavenly bodies) ever has undergone and always will undergo is locomotion. Aristotle does not present this explanation anywhere in the argument for locomotion’s priority in essence explicitly. As is so often the case, the argu- ment is rather compressed and presupposes a number of assumptions that are left unsaid. But at the beginning of the fourth argument, as we have seen, Aristotle at least states that “for eternal things it is only possible to change with respect to this change”, i.e. locomotion.88 One—but, as has 88 τοῖς γὰρ ἀϊδίοις μόνον ἐνδέχεται κινεῖσθαι ταύτην, Phys. VIII 7, 260b29–30. This is clear also from the fact that the heavenly element, aether, according to Cael. I 3, 270a12–35, Conclusion: Locomotion’s priority in essence 209 ISBN Print: 9783525253069 — ISBN E-Book: 9783647253060 © 2014, Vandenhoeck & Ruprecht GmbH & Co. KG, Göttingen