Moral Vagueness: A Dilemma for Non-Naturalism

This chapter explores the implications of moral vagueness for non-naturalist metaethical theories like those recently championed by Shafer-Landau, Parfit, and others. It characterizes non-naturalism in terms of its commitment to seven theses: Cognitivism, Correspondence, Atomism, Objectivism, Supervenience, Non-reductivism, and Rationalism. It starts by offering a number of reasons for thinking that moral predicates are vague in the same way in which “red,” “tall,” and “heap” are said to be. It then argues that the moral non-naturalist seeking to countenance moral vagueness faces a dilemma: are moral properties vague, or perfectly sharp? On either horn of the dilemma, serious problems arise for some of the central tenets of non-naturalism: vague properties seem to threaten Objectivism, Supervenience, and Non-reductivism; on the other hand, sharp properties raise problems for Supervenience and Rationalism. The difficulties on each horn of the dilemma are real, and while they may not be insuperable, they do, at the very least, drastically limit the things non-naturalists can consistently say about moral properties, facts, and reasons.