Moral principle explanations of supervenience

Non-naturalists realists about morality face the challenge of explaining the supervenience of the moral facts on the natural facts. An influential recent suggestion, developed by Scanlon (2014) and Fogal and Risberg (2020), is that the non-naturalist can easily explain supervenience by appealing to explanatory moral principles, or metaphysical laws. The idea is that the general moral principles are necessary and so trivially supervene on the natural facts, while the particular moral facts are explained by the general, necessary, moral principles and the natural facts so they supervene on the natural facts too. I argue that such a strategy is unsuccessful. Either it (i) fails to explain supervenience because it doesn't correctly identify the difference-makers for supervenience, or it (ii) does explain supervenience, but only by postulating another striking fact-and it cannot give a satisfactory explanation of this fact that properly identifies the difference-makers. Making sense of supervenience is one of the key challenges for a non-naturalist metaphysics of modality. Views based on moral principles look like they fail this challenge. Consequently, the non-naturalist should look to other metaphysical machinery to develop their view.