ABSTRACT
According to the companions-in-guilt objection to moral error theory: If the arguments for the moral error theory are sufficient to establish that the moral error theory is true, then those arguments are sufficient to establish that the epistemic error theory is true (the parity premise). The epistemic error theory is false (the epistemic existence premise). So, the arguments for the moral error theory are not sufficient to establish that the moral error theory is true. I defend a new response this objection. I first argue that the moral and epistemic properties that are the truth-makers of moral and epistemic judgments are categorical moral and epistemic reasons of rationality, such that “practical rationality yields ... reasons”. Categorical reasons are constituted by causal relations and desires that we are rationally required to have regardless of any other desires that we may have (and hypothetical reasons are constituted by causal relations and desires that we are rationally permitted but not required to have), where which desires and beliefs we are rationally required and permitted to have is determined by rational requirements like the requirement to believe what we have complete evidence to believe. Second, I defend an account of the subject-matter of morality on which moral norms govern human interactions and concern the welfare of all sentient beings. Finally, I argue that practical rationality yields categorical reasons with epistemic but not with moral subject-matter, since there are no rational requirements to muster desires with moral content (or to abandon desires with immoral content). The parity premise in the companions-in-guilt objection to moral error theory suggests that the metaphysical structure of moral and epistemic reasons fully determines the fate of their existence, but this is not true as their subject-matter makes an important difference.
