Readers of my blog know that I have been debating whether the is/ought dichotomy is compatible with theistic metaethical realism . I’ve taken the stance the odds the is/ought dichotomy is true are at least as probable as the odds the is/ought dichotomy is false. Since the is/ought dichotomy is incompatible with theistic metaethical realism, and there are more ways to be a moral realist who denies the is/ought dichotomy than theistic metaethical realism, the odds theistic metaethical realism is true are less than 50%; thus, theistic metaethical realism is not obviously true. The preceding argument can be extended further: since theistic metaethical realism is less than 50% likely to be true, we should not be theistic metaethical realists. In place of theistic metaethical realism, I have suggested metaethical non-natural realism: the view that there are non-reducible objective moral truths that constitute their own fully autonomous domain of facts. Richard Bushey has argued the is/ought dichotomy and theistic metaethical realism are compatible , but, thus far, I have found his substantive challenges unconvincing. Here, I respond to another possible argument that the theist may provide against meta-ethical non-natural realism.
The theist may argue that, if the meta-ethical non-natural realist is correct, then it is difficult to explain how we know what moral truths there are. Moral truths would not have any spatial or temporal location, so we cannot observe them in the world; they would have no causal efficacy, so they could not cause various events that we observe; and our brain’s access to non-physical moral truths is mysterious. But, the theist may argue, theistic metaethics does not suffer from these problems. For theistic metaethics, God produces all moral truths, which He communicates to us through divine revelation . The argument can be put formally as follows: