Supervenience, Repeatability, & Expressivism

Expressivists traditionally explain normative supervenience by saying it is a conceptual truth. I argue against this tradition in two steps. First, I show the modal claim that stands in need of explanation has been stated imprecisely. Classic arguments in metaethics for normative supervenience and those that rely on it as a premise presuppose a constraint on the supervenience base that is rarely (if ever) made explicit: the repeatability of the non-normative properties on which the normative supervenes. Non-normative properties are repeatable when it is possible for numerically distinct individuals to share them. Second, I show if the modal truth that stands in need of explanation entails that there are individuals exactly alike in repeatable non-normative respects that cannot normatively differ, then standard expressivist accounts of normative supervenience as a conceptual truth are unsuccessful. Expressivist metasemantics for normative terms, together with constitutive facts about the non-cognitive attitudes essentially involved in normative thought, strongly suggest that repeatable supervenience could not be a conceptual truth. I argue, finally, that although repeatable supervenience bears the marks of a conceptual truth, expressivists should be content to treat it as an ordinary normative truth, and to explain it the same way they explain other normative truths.