Frankfurt Cases and Overdetermination

For nearly forty years now, Frankfurt cases have served as one of the major contributors to the compatibilist's cause with respect to moral responsibility. These cases typically involve a causally preempted condition that is supposed to guarantee a choice without causing it. This has had the effect of softening up some to the idea that determinism does not exclude moral responsibility simply in virtue of guaranteeing a unique future. I believe that these traditional Frankfurt cases adequately support this cause. But I also believe that the traditional versions of Frankfurt cases suffer from some rhetorical defects.My strategy is as follows. First, I want to respond to a dilemma that has been raised by some libertarians against arguments utilizing Frankfurt cases. This dilemma has the effect of raising a question-begging charge against such arguments. Part of my response is to draw attention to the relevant principle that I think Frankfurt cases should really target, a principle slightly different from Harry Frankfurt's original Principle of Alternate Possibilities. Second, I elaborate and defend the claim that traditional Frankfurt cases involve causal preemption.