“Ought” Implies “Can” but Does Not Imply “Must”: An Asymmetry between Becoming Infeasible and Becoming Overridden

The claim that (OIC) “ought” implies “can” (i.e., you have an obligation only at times at which you can obey it) entails that (1) obligations that become infeasible are lost (i.e., you stop having an obligation when you become unable to obey it). Moreover, the claim that (2) obligations that become overridden are not always lost (i.e., sometimes you keep having an obligation when you acquire a stronger incompatible obligation) entails that (ONIM) “ought” does not imply “must” (i.e., some obligations are not all-things-considered). It is standard to infer ONIM—via (2)—from the premise that becoming overridden can result in “moral residue” (e.g., in the appropriateness of feeling regret). But then, I note, one could similarly infer not-OIC—via not-(1)—from the premise that becoming infeasible can result in moral residue. So there is an argument against OIC which parallels the standard argument for ONIM. I respond by rejecting both arguments: it is a mistake to always infer from the presence of moral residue that an obligation is not lost. Then I propose new arguments both for ONIM and for OIC.