 Despite their differences, optimalism and (Truth Supervenes Upon Being) share a key idea in common—that a negative existential truth isn’t true because something exists, but because something doesn’t, viz. a truth-maker for its contradictory, a false-maker for it. C.B. Martin has objected that this doesn’t obviate the need to posit truth-makers for negative existentials. This is because a statement that there are no false-makers for a negative existential truth is itself a negative existential truth. So this statement “can’t be used to explain or show how the latter needs no truth-making state of the world for it to be true” (1996: 61). Lewis takes Martin’s objection to be that this account of the truth of negative truths isn’t informative. Take the statement that there are no unicorns. Why is it true? Well because there are no unicorns. That’s not much of an explanation! But, Lewis retorts, the positive existential statement that there is a cat is true because there is a cat. That’s “No explanation at all, and none the worse for that” (Lewis 2001: 611–12). Fair enough; but perhaps Martin meant that optimalists and their fellow-travellers were presupposing what they set out to show—because they assumed without argument that a special class of negative claims stood in no need of truth-makers, those according to which other negative statements lacked false makers.