A ristotle on Zeno and the now

Abstract

If we accept the textual emendations favoured by W. D. Ross in his edition of the Physics, Aristotle, we must believe, reported an argument of Zeno's and gave a reply to it in the following words (or something very like them) inZ,ch.9(239b5-9): 'Zeno's argument is unsound. For he says that if (1) everything is always at rest when it is over against what is equal to it, and (2) the moving object is always in this condition in the now, then (3) the moving arrow is motionless. But this is false, since (4) time is not composed of indivisible nows, any more than any other magnitude is composed of indivisibles.' Aristotle briefly recapitulates both argument and reply later in the chapter (239 b 30-33), where he says: 'The third argument is the one I have just mentioned, that the moving arrow is at rest. This conclusion follows from the assumption that time is composed of nows. If this is not granted, the argument will not go through.' What exactly did Aristotle think Zeno's argument consisted in? And what was his reply? I shall try to determine the answers to these questions. To do this is not to determine what Zeno's argument was, but it is intimately related to it. The answer one gives to these questions depends in part on the way in which one interprets the expressions 'in the now' (6v Tup vvv) and 'of indivisible nows' (kx Tr&v vvv rCv &8LaLp&Frwv) that occur in the main passage, and the expression 'of nows' (ix 'rCv viv) that occurs in the recapitulation. Are they intended to refer to extensionless points in time, time-instants, or to atomic periods of time, or are they vaguer, referring to indivisible time-elements whose nature, as extended or extensionless, is not specified? Professor Vlastos supports the second interpretation. (See 'A Note on Zeno's Arrow' in Studies in Presocratic Philosophy, vol 2, edd. R. E. Allen and D. J. Furley, p. 187 and notes 13 and 21 on pp. 196-7). In favour of this view he argues that there is at least one other passage in the Physics (Z, ch. 1, 231 b 18-232 a 24) where it is reasonable to suppose that Aristotle uses the expression 'rO VVV' to refer to an atomic period of time. If we accept Vlastos' interpretation, our answers to the two questions that