A "Flow" of Time, or a Transient "Now"?
A "Flow" of Time, or a Transient "Now"?
It seems to me very strange that students of McTaggart (he is famous for his "proof" of unreality of time, on the basis of the "contradiction" derived from a "moving now", which he regards as indispensable for our notion of time), including tense-logicians, seldom refer to works on relativity or philosophy of physics, and conversely, philosophers of spacetime seldom refer to McTaggart's "proof" of unreality of time (a notable exception is P. Horwich, Asymmetries in Time, MIT, 1987). This situation may seem understandable, because McTaggart's argument seems quite "a priori" and does not seem to have anything to do with relativity, or physics in general.
However, there are some important works in the philosophy of spacetime, which seem quite relevant to the basic problem McTaggart treated. For instance, Gruenbaum's argument in the Chapter 10 of Philosophical Problems of Space and Time is quite instructive.
He first distinguishes between the question of "anisotropy" of physical time and that of the "flow" of time; the latter may suggest "the direction" of time, but the anisotropy of time provides no warrant for singling out "the direction". Then, is there any hope for determining "the direction" of time, on the basis of physics (not on the basis of common-sense notions)? Reichenbach tried to do so. But Gruenbaum, drawing on Hugo Bergmann's criticism, maintains that any such attempts are bound for a failure.
I maintain with Bergmann that the transient now with respect to which the distinction between the past and the future of common sense and psychological time acquires meaning has no relevance at all to the time of physical events, because it has no significance at all apart from the egocentric perspectives of a conscious (human) organism and from the immediate experiences of that organism. (op. cit., 324)
The reader should read his argument. If this is correct, then it can give a physical content to some part of McTaggart's argument, although, of course, Gruenbaum would not agree with McTaggart on the unreality of (physical) time!
Last modified March 27, 2003. (c) Soshichi Uchii