Source incompatibilism and alternative possibilities

The claim that moral responsibility for an action requires that the agent could have done otherwise is surely attractive. Moreover, it seems reasonable to contend that a requirement of this sort is not merely a necessary condition of little consequence, but that it plays a decisive role in explaining an agent's moral responsibility for an action. For if an agent is to be blameworthy for an action, it seems crucial that she could have done something to avoid this blameworthiness. If she is to be praiseworthy for an action, it seems important that at least she could have done something less admirable. Libertarians, in particular, have often grounded their incompatibilism precisely in such intuitions. By contrast, I shall argue that the availability of alternative possibilities is in a significant sense irrelevant to explaining an agent's moral responsibility for an action. At the same time I do not want to disavow incompatibilism, but rather to defend a version in which the pivotal explanatory role is assigned to features of the causal history of the action, and not to the availability of alternative possibilities.