Simon Blackburn’s supervenience argument—focusing on the mysterious “ban on mixed worlds”—is still subject to a variety of conflicting interpretations. In this paper, I hope to provide a defense of the argument that clarifies both the argument and the objections it must overcome. Many of the extant objections, I will argue, fail to engage the argument in its true form. And to counter the more compelling objections, it will be necessary to bring in additional argumentation that Blackburn himself does not clearly (...) provide. One important upshot of this discussion is that moral realism is not the only target of the argument: it raises trouble for a variety of metaethical views wed to realist-friendly construals of moral evaluation. Rightly understood, this argument not only survives the prominent responses, but turns out to be more powerful than his critics and Blackburn himself have recognized. (shrink)

In the 1970s and 1980s, Simon Blackburn published a number of much-discussed works in which he argued that the supervenience of the moral on the natural generates a serious problem for moral realism, a problem which his own brand of moral projectivism can avoid. As we will see below, Blackburn construed moral supervenience in terms of what is known as weak supervenience. Partly in response to Blackburn, a number of philosophers have argued that weak supervenience is too weak to capture (...) the intuitive sense in which the moral supervenes on the natural. Instead, it is argued, we should opt for strong supervenience, and, further, that strong supervenience completely disables Blackburn's argument against moral realism. This idea – that strong supervenience undermines Blackburn's argument – is very common in recent metaethics, and the purpose of the present paper is to develop a challenge to this near-orthodoxy. (shrink)

One of the most familiar arguments for expressivist metaethics is the claim that the rival theory, moral realism, cannot provide a satisfying explanation of why moral properties supervene on natural properties. Non-cognitivism, however, has its own problems explaining supervenience. Expressivists try to establish supervenience either by second-order disapproval of type-inconsistent moral evaluations or by pragmatic considerations. But disapproval of inconsistency is merely a contingent attitude that people happen to have; and pragmatic justification does not allow for appraisers to take their (...) own moral attitudes seriously enough. What has been overlooked is a third alternative. The metaethical theory that can best account for supervenience is neither realist nor non-cognitivist but an objectivist version of constructivism. On the constructivist theory, right and wrong are determined by the principles that people would (hypothetically) consent to under ideal conditions. Type-consistency is a required feature of any principles regulating our conduct, if they are to be freely agreed to by ideally rational people. (shrink)