I. Presentism and Eternalism

The problem of defining time concerns the status attributed to the present.

Since at least Saint Augustine,understanding time from the present only leads to confusion. The past is not, since it is no longer present; the future is not, since it is not yet present; and the present is only insofar as it slips by and is already no more, since its being is to become. Augustinian confusion essentially comes from the desire to define the present as presence (to the mind), and presence as being or as existence. The present is what is present, and what is present is what is.

On the other hand, understanding time without invoking the present, by restricting oneself to the order of events before and after, allows the creation of a series organising what is prior and what is subsequent, but which does not exist – for example, as we see in McTaggart's analysis of the connection between past, present, and future in 'The unreality of Time'.

Two possibilities emerge. Either the past, present, and future are equally real, in which case the present is no longer really present (since it is no longer a distinguished presence, but only one presence among others); or the present is really present, in which case the past and future are no longer really real. One never carries the theoretical day on all fronts.

Trenton Merricks writes: