 Fourth, Lewis holds that his thesis of Humean Supervenience is, at best, only contingently true. Of course, given that he recognizes the (metaphysical) possibility of perfectly natural, non-spatiotemporal relations, he should treat HS as at best contingent. But he advances reasons for doing so of a quite different sort. They are not particularly good reasons, and so we will pass them by; but see the supplementary document on