This is the text of The Lindley Lecture for 1962, given by Arthur N. Prior (1914-1969).

There are ways in which the new tenseless theory of time is analogous to David Lewis’s modal realism. The new tenseless theory gives an indexical analysis of temporal terms such as ‘now’, while Lewis gives and indexical analysis of ‘actual’. For the new tenseless theory, all times are equally real; for Lewis, all worlds are equally real. In this paper I investigate this apparent analogy between these two theories, and ask whether a proponent of one is committed, by parity of (...) reasoning, to the other. I conclude that the analogy is merely apparent, and that independent reasons are needed to support each theory. (shrink)