Hume’s Dictum and Metaethics

This paper explores the metaethical ramifications of a coarse-grained criterion of property identity, sometimes referred to as Hume's dictum. According to Hume's dictum, properties are identical if and only if they are necessarily co-extensive. Assuming the supervenience of the normative on the natural, this criterion threatens the non-naturalist view that there are instantiable normative properties which are distinct from natural properties. In response, non-naturalists typically point to various counterintuitive implications of Hume's dictum. The paper clarifies this strategy and defends it against objections by Bart Streumer and Ralf Bader. In addition, it is argued that proponents of naturalist and supernaturalist views, along with proponents of a certain kind of nihilism, should also reject Hume's dictum. This shows that non-naturalists can also attack the criterion indirectly, by pointing to partners in guilt. Also, it shows that not just any opponent of non-naturalism can appeal to Hume's dictum. Only certain nihilists can.