 What about perfectly natural relations? Here matters are less clear. Lewis certainly thinks that spatiotemporal relations are perfectly natural; what is less obvious is whether, by his lights, physics could rationally lead us to reject this claim. For now I will simplify, and have Almost-Lewis add a fifth constraint—one that is in tension at least with the spirit of the fourth, and that the real Lewis certainly rejects. It is this: not only are spatiotemporal relations perfectly natural, they are the only perfectly natural relations. (The only possible ones—though remember that given Lewis’s reductionism about modality, that is an idle addition.)