  Nonetheless, Baldwin is mistaken to suppose that this entirely disarms the argument from supervenience. Baldwin might well show that Blackburn cannot escape the charge of proving too much simply by appealing to the thesis that supervenience in the moral case is a priori. Showing that Blackburn’s move does not explain why the argument would not prove too much still does not provide a satisfactory defense of non-naturalism, though. For if the non-naturalist simply appeals to conventional and linguistic facts then they might well explain why it is analytic that if there are any moral properties then they must supervene on the natural (and non-moral) ones. The original objection, though, was a metaphysical one rather than a semantic one. The problem for the non-naturalist now becomes one of explaining how the non-natural properties in question could satisfy the relevant supervenience constraints and hence count as moral in the first place. The challenge is to provide a metaphysical account of how there could be properties like the properties to which the non-naturalist maintains our moral vocabulary purports to refer. Otherwise we are left either with the error-theoretic conclusion that there are no moral properties or the non-cognitivist conclusion that moral vocabulary does not even purport to refer (in the sense of ‘refer’ in play when one does serious metaphysics, anyway; again, the non-cognitivist will allow that we can ‘speak with the vulgar’ here). So there is still a problem for the non-naturalist. Nonetheless, Baldwin seems right in that the appeal to analyticity seems not to have done the work for which it was invoked by Blackburn. For it again seems as if the argument from supervenience generalizes to other cases of supervenience without reduction. Perhaps the non-naturalist’s critics should simply embrace this implication but argue that the prospects for reduction in these other cases are much brighter than the non-naturalist suggests they are.