I am trying to wrap my head around different philosophical concepts of 'forever'. Correct me if I'm wrong, but I believe there to be three versions of 'forever' in terms of temporal duration:
- Strictly eternal, timeless and atemporal: there is no time.
- Actually sempiternal, or actual infinite temporal duration: there is time but it has neither beginning or end (as per Aristotle).
- Potentially sempiternal, or potential infinite temporal duration: there is time and it has a beginning but has no end; the temporal duration from the beginning to now is always finite, but the infinite addition of time makes it potentially infinite.
There is also the 'non-forever' case of truly finite temporal duration in which time has both a beginning and an end.
What is puzzling me is what is time that has an infinite past but will come to an end. The temporal duration of the past is actually infinite, but the fact that will come to an end makes it potentially finite. If we cannot know the future and therefore cannot measure future duration, is it infinite until it's not in the same way that case 3 above is finite until it's not? The main difference is that one never gets to crossover to the infinite in case 3, but one does cross to finite time in this last case.