Eternalism

Eternalism's strongest scientific support comes from special relativity's relativity of simultaneity: two events that one observer, moving at a certain velocity, judges to happen at exactly the same moment, another observer, moving differently, will judge to happen at different times, with neither observer's frame of reference privileged as the correct one, which makes the very idea of a single, objective present moment shared across the universe difficult to sustain physically.

If there is no privileged present, eternalists argue, then there is no principled physical basis for saying the past has ceased to exist while the future has not yet begun to; instead, all events at all times are equally real, differing from one another only in their position along the time dimension, much as different places differ only in their position along a spatial dimension, an analogy that gives the view its common name, the block universe. On this picture, change and the felt passage of time are not features built into the fabric of reality itself but features of how a conscious observer, embedded at one location within the block, experiences moving through it, in something like the way a person reading a novel experiences the story unfolding page by page even though the entire book, beginning to end, already exists complete on the shelf.

Eternalism sits uneasily against most religious pictures of time, which generally treat the future as genuinely open, not yet decided, and treat human choices as making a real difference to what becomes real rather than merely revealing what, in some higher sense, was already there all along; process theology in particular was developed specifically to preserve this kind of openness against any deterministic or eternalist block, insisting that even God experiences time's passage and does not simply survey a completed four-dimensional universe from outside it.

Eternalists reply that the metaphysical reality of all moments existing does not by itself settle whether the future is determined or undetermined, since a block universe can, in principle, still contain genuinely undetermined events at later coordinates, so eternalism and determinism, though often discussed together, are not strictly the same claim and need not stand or fall together. The dispute with presentism remains largely unresolved within physics itself: relativity is widely taken as strong evidence for eternalism, but some philosophers of physics argue a suitably reformulated presentism, keyed to each observer's own reference frame rather than to a single universal now, can still be made consistent with relativistic physics, keeping the debate active rather than settled by science alone.