  Arguably the moral case is different from these other cases of supervenience without reduction because the supervenience of the moral on the natural (and non-moral) is analytic. Plausibly, someone who thinks two things could differ morally but be identical in all other respects does not fully grasp the meanings of moral predicates. This is not nearly so plausible in other cases in which we seem to have supervenience without reduction. Cartesian dualists can deny supervenience and their view does not seem conceptually incoherent however mistaken it may be. As Blackburn argues, if this sort of error is a conceptual one then “whole cultures have been prone to denial of an analytic truth” (Blackburn 1985: 59) which at best seems unlikely. The idea here seems to be that the only way a realist could explain supervenience qua analytic truth would be to hold that the moral is analytically identical to some property that can also be characterized in purely naturalistic terms. The non-naturalist, of course, is committed to rejecting any such analyses so if this is the only way to explain the analyticity of supervenience then non-naturalists cannot explain it. In which case, the appeal to analyticity might seem to block the ‘proves too much objection’.