Full Idea
McTaggart's proof of time's unreality: A-series positions (past, present and future) are mutually incompatible, so no event can exhibit more than one of them; but since A-series events change position, all events have all A-series posititions. Absurd!
Gist of Idea
A-series time positions are contradictory, and yet all events occupy all of them!
Source
report of J.M.E. McTaggart (The Nature of Existence vol.2 [1927]) by Robin Le Poidevin - Travels in Four Dimensions 08 'McTaggart's'
Book Reference
Le Poidevin,Robin: 'Travels in Four Dimensions' [OUP 2003], p.131
A Reaction
I'm not convinced that this is any more contradictory than someone being married at one time and unmarried at another. No one is suggesting that an A-series event can be both past and future simultaneously.
Related Idea
Idea 22935 The B-series can be inferred from the A-series, but not the other way round [McTaggart, by Le Poidevin]