Frankfurt Cases and Overdetermination

I

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. The reasons here are two-fold: I wish to carefully distinguish and clarify some important varieties of overdetermination, and I also want to offer some defense of the traditional Frankfurt arguments. But third, and most important, I suggest that we move beyond Frankfurt cases involving causal preemption. I will argue that the compatibilist gains a rhetorical advantage by shifting to cases in which an agent's choice is genuinely causally overdetermined.

II Catching up on the Dialectic

An incompatibilist about moral responsibility is one who thinks that moral responsibility is not compatible with determinism. Incompatibilists of old were likely to endorse something like the following argument:

Premise 1. Determinism rules out alternative possibilities. In a deterministic world there is only one nomologically possible future given the conditions of the world at any given time.

Premise 2. Moral responsibility requires alternative possibilities (e.g., the ability to choose otherwise).

Conclusion. Since determinism rules out the ability to choose otherwise, determinism is incompatible with moral responsibility.

Premise 2 of this argument is Frankfurt's Principle of Alternate Possibilities (PAP).¹

PAP: A person is morally responsible for an action or choice only if he had alternative possibilities to that action or choice (i.e., could have done or chosen otherwise).

Frankfurt attacked PAP by providing counter-examples —cases in which someone supposedly lacked alternative possibilities, but was morally responsible anyway. Such counter-examples, Frankfurt cases, deny Premise 2 of the above argument for incompatibilism and issue a challenge to incompatibilists: Either construct a different argument for incompatibilism or disprove the alleged counter-examples. Many have opted to pursue the latter. This article offers a partial defense of Frankfurt's strategy in response to these objections. I defend Frankfurt cases against a dilemma that is raised by various libertarians. Further, I argue that in order to avoid another common set of objections —so-called flickers of freedom —and to otherwise focus debate it is better to shift discussion from traditional Frankfurt cases to cases involving genuine overdetermination that, I believe, better meet Frankfurt's original intentions.

Let us first get a concrete example of a Frankfurt case before us. The following is adapted from an example offered by John Martin Fischer²:

Jones is in a voting booth deliberating whether to vote for Bush or Kerry. Unbeknownst to Jones, a neurosurgeon, Black, has implanted a mechanism in Jones's brain that allows Black to monitor Jones's neural states and alter them if need be. Black is a diehard Democrat, and should Black detect neural activity indicating that a choice for Bush is forthcoming, Black is prepared to activate his mechanism to ensure that Jones instead chooses to vote for Kerry. As a matter of fact, Jones chooses on his own to vote for Kerry, so Black never intervenes.

This is a prior sign Frankfurt case with a counterfactual intervener. Black did not actually intervene (so his 'intervention' is only counterfactual), but he would have intervened had he observed different neural activity (the prior sign). This...