Metaethical Lessons of a Failed Ontological Proof of Robust Moral Realism

Abstract Michael Huemer claims to give an ontological proof of robust moral realism, the influential view that we have non-selfish, categorical, observer-independent reasons for action. This paper argues that one of Huemer’s premises – that knowing that baby torture is not objectively wrong would provide us with no first-person reasons to torture babies – is false of agents with sadistic desires. This in turn falsifies Huemer’s further premise that the premises of his “Antitorture Argument” are true independent of interests, desires, or other attitudes. My refutation is then shown to not only deepen extant doubts about whether robust realists can adequately account for the first-person normative authority of morality. It also suggests that realists about categorical moral reasons must either complete a project – moral constructivism – which has never clearly succeeded, or else defend views on the nature of categorical reasons that strain credulity and beg the question against their opponents.