時間の「方向」

Abstract

This paper examines the common view that time is "unsymmetrical" or has a "privileged direction." An examination of some uses of the word 'direction' in ordinary language leads to the conclusion that reference to "direction" is permissible either in connexion with motions and changes or in connexion with the relative spatial orientation of bodies. In all such literal senses, reference to the "direction" of time is unintelligible. The underlying metaphor of time as a flowing stream is held to be absurd, because it requires reference to a "super-time" in which ordinary time can "flow." An attempt is then made to analyse what is meant by saying that space is "isotropic, " with a view to deciding whether time isotropic or not. A distinction is made between the "order" and the "arrangement" of bodies placed along a line; the identification of a particular arrangement is held to involve the use of what is here called an "incomplete relation" (one involving the relative orientation of an observer). In science, it seems, both time and space are treated as "isotropic." Hence, if the entire history of the universe were "run backwards, " nothing in the scientific description of the universe would be changed. But while this is true of science, ordinary uses of 'earlier than' and other temporal expressions show an absolute distinction between the two possible arrangments of a temporal series of events. It is misleading to refer to this feature of uses of temporal words by saying that time has a "direction." Talk about time's "direction" is a symptom of conceptual confusion.