Frankfurt cases, alternative possibilities and agency as a two-way power

In this paper, I argue that having ‘leeway’ is part and parcel of what it is to be the agential source of an action, so that embracing source incompatibilism does not, by itself, absolve the incompatibilist of the need to find Frankfurtian agents to be possessors of alternate possibilities. I offer a response to Frankfurt-style counterexamples to the Principle of Alternate Possibilities, based on the idea that Frankfurt's Jones exercises the two-way power of agency when he acts – a power whose exercise intrinsically implies the possibility of having done otherwise. I then show how to respond to the objection that the alternative possibility noted is not sufficiently ‘robust’ to ground his moral responsibility. I also distinguish my own argument for the claim that source incompatibilism is not truly independent of leeway incompatibilism from an argument for the same conclusion which has been offered previously by Kevin Timpe, and suggest that my own version has the dialectical advantage that it does not automatically assume from the outset that sourcehood requires indeterminism, and hence is in line with the traditional idea that the alternate possibilities requirement on moral responsibility is the common property of compatibilists and incompatibilists alike.