This essay is the first act of a two-act play. My ultimate aim is to defend a simple proposition: time passes. To be more precise, I want to defend the claim that the passage of time is an intrinsic asymmetry in the structure of space-time itself, an asymmetry that has no spatial counterpart and is metaphysically independent of the material contents of space-time. It is independent, for example, of the entropy gradient of the universe. This view is part of common-sense, (...) but has been widely attacked by philosophers. The passage of time, we are told, is a myth, an illusion, even an incoherent notion. Because the notion that time passes is common sense, it perhaps requires little positive defence; if there are no weighty objections to the view, it ought to be accepted. So the first, and more important, act of the play is defusing the arguments which have been used to cast doubt on the passage of time. I have positive arguments to give, but not having space for them here, I will confine myself to an examination of the common philosophical arguments that have been used to cast doubt on the passage of time. (shrink)