Conceptually born from the seemingly diametrically opposed notions of
apocalypse and
stasis, apocatastasis is the name of the belief that the
end of the world (in whatever form such might take) would ultimately result in a restoration of the conditions from which it first arose, or existing before the world came about at all. This is not especially a theological notion, as it is possible that such a condition could arise in a world utterly lacking in spiritual import. Indeed, the idea was first developed amidst not-especially-theological
rumination, with those reliable ancient Greeks hypothesizing that the purely physical conditions from which things have come may be the conditions to which things will go. But, the idea went on to be a great subject of debate in early
Christianity. Would
God, especially if we speak of an unchanging God, in ending the world, in fact bring about the same conditions as preceded it? And would these same conditions then inspire a new
Creation? For if God is unchanging, then God's inclination to create once Creation is absent would be unchanging as well.
More modernly, an almost
science-fiction-delving variation of the notion has been discussed, even by serious physicists, wherein our world is in some sort of temporal loop, happening over and over and over again, with exactly the same set of occurrences and outcomes. Alternately, it is supposed that the world begins anew each time with the same initial conditions, but that some tiny fluctuations occur in their unfolding which leads either to vastly different realities or (in a highly unlikely manner, which really is relegated to science fiction) realities which are nearly identical but present subtle distortions. These might themselves be considered
parallel universes, for although they are ordered in time, they don't know this. Once each ends, so ends time within it, and the next one forms, essentially outside of time (or, at the least, outside of the time of any other), and so oddly enough all can exist simultaneously, even though each came after one and before another.