Abstract

Sometimes, a metaphysical theory has revisionary ethical consequences: for example, some have thought that modal realism entails that there are no moral obligations. In these cases, one may be tempted to reject the metaphysical theory on the grounds that it conflicts with commonsensical ethics. This is an ethics-to-metaphysics inference. My claim is that this inference is in general irrational, and that the fact that a metaphysical theory has highly revisionary ethical consequences is no reason at all to reject the theory. I argue for this claim on the basis of general epistemic principles about the transmission of justification, and what makes for a good argument. Furthermore, I argue that my account can explain why a certain narrow class of ethics-to-metaphysics inferences are rational.