  Simon Blackburn, however, argues that the phenomenon of supervenience especially favors non-cognitivism. According to Blackburn, it is not just the simple fact that moral properties supervene on nonmoral properties that needs to be explained. Nor is it just that appropriate moral predication must supervene on nonmoral predication, to put the point in a way that does not beg the question against non-cognitivism. It is rather to explain how honoring the supervenience constraint can be a requirement of linguistic competence, even while there is no analytic entailment from nonmoral claims to moral claims. In other words, what needs explaining is how supervenience can be a conceptual requirement even while there is no analytic equivalence between moral properties and any non-moral property. Blackburn thinks that we require such an explanation even if there are metaphysically or nomically necessary connections between moral and nonmoral terms or properties. For, he thinks, it is hard to see how such nomic or metaphysical connections could justify the analytic status of the supervenience thesis. People can be ignorant of nomic necessities for it is an empirical matter what natural laws govern our world. And they might be ignorant of certain metaphysical necessities while knowing all the truths about the meanings of their terms. So these necessities cannot justify the apriori and analytic status that the supervenience requirement has. Or to put the same point differently, a requirement to recognize some constraint that one should recognize merely in virtue of having competence with the appropriate terms cannot be explained by citing a fact which mere linguistic competence does not put one in a position to recognize.