 In giving an account of the various aspects of time perception, we inevitably make use of concepts that we take to have an objective counterpart in the world: the past, temporal order, causation, change, the passage of time and so on. But one of the most important lessons of philosophy, for many writers, is that there may be a gap, perhaps even a gulf, between our representation of the world and the world itself, even on a quite abstract level. (It would be fair to add that, for other writers, this is precisely not the lesson philosophy teaches.) Philosophy of time is no exception to this. Indeed, it is interesting to note how many philosophers have taken the view that, despite appearances, time, or some aspect of time, is unreal. In this final section, we will take a look at how three metaphysical debates concerning the nature of the world interact with accounts of time perception.