Space-Time and the Direction of Time

Abstract

Since McTaggert, two philosophical theories of time have become current, the tensed and the tenseless. Most philosophers impressed with relativity and relativistic space-times have held the tenseless theory. The tensed view has appealed to those philosophers who have relied on ordinary language and common sense for their philosophic wisdom. While I agree that the tenseless rather than the tensed is the appropriate conception of time for a relativistic space-time, I also think the tensed view contains an important insight. In what follows I will show how this insight of the tensed view can be incorporated into the relativistic space-time conception of the universe. According to the tensed theory, it is an objective, irreducible and fundamental feature of the universe that events are continually changing with respect to their being past, present, and future and it is this continually changing or 'moving' present (or becoming) that imposes a direction or arrow on time. At each moment, the arrow points into the future, the direction into which the present moves. Temporal relations are then reduced to, or explained in terms of this moving present. An event (moment) G is earlier than an event (moment) F iff the present moves from G to F i.e, F is in the future of G; G is simultaneous to F iff G and F are copresent, etc. Put differently, temporal relations are explained in terms of the direction or arrow of time, an event (moment) G being earlier than F iff the arrow at G points towards F. The tenseless theory, on the other hand, rejects the idea of an objective, moving present and with it the idea that events (or