According to the principle of alternate possibilities (PAP), a person is morally responsible for an action only if he could have done otherwise. PAP underlies a familiar argument for the incompatibility of moral responsibility with determinism. I argue that Harry Frankfurt's famous argument against PAP is unsuccessful if PAP is interpreted as a principle about blameworthiness. My argument turns on the maxim that "ought implies can" as well as a "finely-nuanced" view of the object of blame. To reject PAP on (...) the blameworthiness interpretation, we must reject either this maxim or the finely-nuanced view or some other apparently innocuous assumption. (shrink)