 We shall look at more nuanced reactions to the relativity of simultaneity below, but first it will be useful to introduce an argument that plays somewhat the same role in Minkowski spacetime as McTaggart’s argument did in Newtonian spacetime. Versions of the argument are endorsed in papers by the physicist Wim Rietdijk (1966, 1976) and the philosopher Hilary Putnam (1967), but the presentation here will be based on an example found in Roger Penrose’s book, The Emperor’s New Mind.