Page - 135 - in The Priority of Locomotion in Aristotle’s Physics

the change’s subject, as such changes would involve contrary locomotions. This is because rectilinear locomotion in one direction and in the opposite direction according to Phys. VIII 8 are contraries, which is also in accor- dance with what is said in the discussion of contrary changes in Phys. V 5.58 Hence, in this case as well, a pause between the two different changes is necessary. This implies that rectilinear locomotion from A to B and from B to A cannot occur in one continuous stretch of time, but has to be inter- mitted at some point.59 This, however, is very different in the case of circular motion (κυκλῷ κίνησις) as Aristotle shows in the last part of Phys. VIII 8 (264b9–265a12). According to Aristotle, in contrast to the other kinds of change, it is no pro- blem to consider circular locomotion that is repeated over and over again as one, continuous and eternal change. As we have seen, construing an eter- nal change from any of the other kinds of change always entails the impos- sible consequence that something x undergoes a change and in the same time and respect also undergoes the contrary change. According to Aristotle, the reason why it is possible for circular locomo- tion to be eternal lies in the fact that it differs significantly from all other types of change. Of course, locomotion on a circular path, too, needs to have a starting point as well as an endpoint; yet, in contrast to all other changes the starting point and the endpoint in this case are one and the same and thus cannot be contrary to each other.60 This is made clearer by the following diagram: A B A B Fig.1 58 See Phys. VIII 7, 261b34–36, and V 5, 229b6–10. 59 Another reason that according to Aristotle shows that the change from A to B and the one from B to A need to be contrary changes is that they annihilate each other (see Phys. VIII 8, 262a6–8). 60 See Phys. VIII 8, 264b10–11. Locomotion alone can be one and eternal 135 ISBN Print: 9783525253069 — ISBN E-Book: 9783647253060 © 2014, Vandenhoeck & Ruprecht GmbH & Co. KG, Göttingen