What Are Frankfurt Cases?

Direct Answer

Frankfurt cases are thought experiments introduced by Harry Frankfurt in his 1969 paper "Alternate Possibilities and Moral Responsibility" to refute the Principle of Alternative Possibilities (PAP): the thesis that a person is morally responsible for what she did only if she could have done otherwise. The classic case runs as follows. Jones intends to shoot Smith, and is entirely committed to doing so. Unknown to Jones, a controller, Black, wants Smith dead and has installed a device in Jones's brain that would make Jones shoot Smith even if Jones showed any sign of wavering. But Jones never wavers; he shoots Smith on his own, from his own intention. Black never intervenes. Jones could not have done otherwise — had he wavered, Black's device would have forced him. Yet Jones is clearly morally responsible for shooting Smith: he did exactly what he wanted, for his own reasons, and the counterfactual intervention played no role in his action.

The point of the case is the distinction between the actual sequence and the alternative sequence. What makes Jones responsible is not that he had alternatives, but that his action flowed from his own deliberation and intention — the actual causal history of the act was the right kind. The would-be intervention belongs to a merely hypothetical scenario that never occurred. Frankfurt concluded that PAP is false: moral responsibility requires not the power to do otherwise, but the right kind of actual causation.

The key distinction to grasp is between two ways the thought experiment can be pressed. In the original case, Jones is said to lack alternative possibilities yet be responsible. Critics reply that Jones still retains the ability to will otherwise (Frankfurt later distinguished "can do otherwise" from "can will otherwise"), or that the cases presuppose a residual power of choice that is exactly what is at issue. These replies generate the rich contemporary literature on "robust" Frankfurt cases.

Historical Context

Before Frankfurt, the Principle of Alternative Possibilities was taken for granted on both sides of the free will debate. Libertarians embraced it as the core of freedom; hard determinists argued that because determinism eliminates alternative possibilities, it eliminates responsibility; and compatibilists strained to show that determinism is compatible with the ability to do otherwise in some weakened sense. Frankfurt's paper changed the shape of the whole debate by arguing that the debate's central premise was false: responsibility never needed alternative possibilities at all.

The paper was published in 1969, at the high-water mark of the analytic tradition's confidence in counterexample-driven philosophy. It immediately spawned a massive literature. John Martin Fischer built an entire research program on Frankfurt's insight, developing the "actual-sequence" approach to responsibility that culminated in the theory of guidance control. Compatibilists of nearly every stripe now begin from Frankfurt's cases; the burden shifted to incompatibilists to reconstruct what free will could require if alternative possibilities are not needed.

Key Arguments & Debates

The central argument for Frankfurt's conclusion is the intuition that Black's device, never activated, has no causal bearing on Jones's act: it is a mere counterfactual safety mechanism. Moral assessment, Frankfurt claims, should track the actual causes of action. If responsibility depended on hypothetical alternatives, then two agents who act identically from identical motives would differ in responsibility solely because one had a hidden controller standing by — an absurd result. This is the strongest form of the argument: the "flicker of freedom" that incompatibilists try to find in the cases (a residual sign of choice that Black must monitor) is either too thin to ground responsibility or reintroduces the alternative possibilities Frankfurt aimed to eliminate.

The incompatibilist response has taken two main forms. First, the "flicker of freedom" strategy: even in Frankfurt cases, the agent has a flicker — a moment of genuine choice, or the ability to will otherwise — and this flicker, not the action itself, is what grounds responsibility. Second, the "sourcehood" strategy: what Frankfurt cases show is not that responsibility is compatible with determinism, but that responsibility is a matter of sourcehood — the agent being the ultimate origin of her action. Since determinism also destroys ultimate sourcehood, the cases do not help compatibilism after all. The debate continues over whether Frankfurt's insight supports compatibilism or merely relocates the incompatibilist requirement.

Contemporary Relevance

Frankfurt cases remain central because the question of "could have done otherwise" is built into everyday moral and legal practice. Criminal law's excuse of duress and its treatment of "choice" in sentencing presuppose some version of PAP; if Frankfurt is right, the law's fixation on hypothetical alternatives is misplaced and should be replaced by attention to the actual causes of behavior — a shift with major implications for how courts assess responsibility in cases involving coercion, brain injury, addiction, and programming. In the age of AI, the cases also illuminate machine responsibility: whether an AI can be responsible depends on the actual causal structure of its decisions, not on whether it could have done otherwise — which makes Frankfurt's distinction a tool for thinking about autonomous systems that are fully determined by their design yet perhaps responsible in the relevant sense.

Related Concepts

• Moral Responsibility: the concept the cases illuminate.
• The Consequence Argument: the incompatibilist argument Frankfurt's insight was used to counter.
• Compatibilism: the position the cases support.
• The Manipulation Argument: the incompatibilist counterattack.
• Reasons-Responsiveness: the theory built on Frankfurt's insight.
• Libertarianism: the position that insists on alternative possibilities.

Further Learning

• Harry G. Frankfurt, "Alternate Possibilities and Moral Responsibility," The Journal of Philosophy 66 (1969).
• Stanford Encyclopedia of Philosophy: Free Will
• Stanford Encyclopedia of Philosophy: Moral Responsibility