It sounds absurd to ask whether time is real — we feel it passing every moment. Yet the question has produced some of philosophy's most rigorous arguments, and modern physics has given it new force. Two separate issues hide inside it: whether time exists at all, and whether the flowing 'present' we experience is a real feature of the world or merely our perspective on it. Both have been answered in startling ways.
The most famous argument that time is unreal comes from J. M. E. McTaggart. He argued that time essentially requires the A-series — the ordering of events into past, present, and future — because without genuine change from future to past, nothing really deserves to be called time. But the A-series, he claimed, is contradictory: every event is past, present, and future, and these are incompatible properties. Attempts to escape by saying an event is present now, past later, and future earlier only smuggle in a second time-series and start the problem over. If time needs the A-series, and the A-series cannot be coherent, then time is unreal. Few accept the conclusion, but the argument has proven remarkably hard to dismiss cleanly, and it forced everyone to say clearly which features of time they take to be fundamental.
Against such skepticism, realists insist that time is as fundamental as anything could be. Change, causation, memory, and experience itself all seem to presuppose time; to deny its reality looks like sawing off the branch we sit on. The realist's challenge is not to prove time exists — that seems obvious — but to say exactly what its reality consists in, and here the debate meets physics head-on.
Block or presentEternalism versus presentism.
Relativity reshaped the question by suggesting that there is no universal, objective 'now.' Because observers in different states of motion can disagree about whether distant events are simultaneous, many philosophers conclude that no single present is privileged — which points toward eternalism, or the 'block universe': the view that past, present, and future are all equally real, laid out in a four-dimensional whole, with 'now' being perspectival, like 'here.' On this picture, dinosaurs and distant future events are every bit as real as this moment; they are simply elsewhere in the block.
The main rival is presentism: the view that only the present moment exists, the past having ceased and the future not yet having come to be. Presentism fits our intuitive sense that only now is real, but it must grapple with relativity's apparent denial of a universal present. A middle option, the growing block, holds that the past and present are real while the future is genuinely open and not yet real. Where you land shapes everything downstream — whether time truly flows, and whether the future is fixed or open. Those questions carry forward into the next pages of this wing.