 The foregoing Almost-Lewisian thesis about spatiotemporal relations is too strong to be tenable: we now have reasonably good reasons, drawn from quantum physics, for holding that even in the actual world, there are perfectly natural relations other than the purely spatiotemporal ones. (Roughly: the relations—whatever exactly they amount to—coded up in the quantum mechanical wave-function.) Two points in its defense are, however, worth brief mention: First, seemingly obvious counterexamples—involving such basic physical relations as being more massive than—in fact aren’t counterexamples, since Lewis can deny that they are genuinely fundamental or perfectly natural, on the basis that facts about their obtaining reduce to facts about the distribution of monadic perfectly natural properties. (Still, they will certainly turn out to be very natural.) Second, if we could at least maintain, as a contingent thesis, that the only perfectly natural relations are spatiotemporal ones, then we could plausibly settle an unresolved and deeply vexed question about the content of physicalism (the doctrine, to put it rather too crudely, that all there is to the actual world is physical stuff), as explained in the supplementary document