Is there a supervenience problem for robust moral realism?

The paper describes the problem for robust moral realism of explaining the supervenience of the moral on the non-moral, and examines five objections to the argument: (1) The moral does not supervene on the descriptive, because we may owe different obligations to duplicates. (2) If the supervenience thesis is repaired to block (1), it becomes trivial and easy to explain. (3) Supervenience is a moral doctrine and should get an explanation from within normative ethics rather than metaethics. (4) Supervenience is a conceptual truth and should be explained by the nature of our concepts rather than by a metaphysical theory. (5) The moral does not supervene on the descriptive, because moral principles are not metaphysically necessary. It concludes that none of these objections is successful, so Robust Realists do have an explanatory debt to worry about.