What Is the Problem of Moral Luck?

Direct Answer

The problem of moral luck is the apparent incoherence of our ordinary practice of moral judgment. The central principle of that practice seems to be that a person can be morally assessed only for what is under her control. Yet in practice we constantly judge people for outcomes that depend on factors beyond their control. Thomas Nagel's classic formulation identifies the paradox: the conditions of moral responsibility (control) and the conditions of ordinary moral assessment (which inevitably involve luck) come apart, and neither can be given up without absurdity.

Bernard Williams introduced the term in 1976 with a striking case. A lorry driver, through no fault of his own — a child runs into the road in a way he could not have avoided — kills the child. Williams argued that the driver experiences a distinct form of "agent-regret": he feels he has something to answer for, a guilt-like residue, even though he is not at fault. If we try to say the driver is fully exculpated because he could not have done otherwise, we miss something essential about the moral life. But if we hold him morally responsible, we are holding him responsible for something outside his control.

Nagel sharpened the problem by distinguishing four kinds of moral luck. Result luck: the drunk driver who swerves past a pedestrian gets a lesser judgment than the one who kills — though the difference is pure chance. Circumstance luck: the person living in Nazi Germany faces moral choices that the person in peacetime never faces; we judge the former by what they did in circumstances they did not choose. Constitutive luck: the kind of person one is — temperament, disposition, capacity for empathy — is largely a matter of inheritance and early environment. Causal luck: the causes that produce one's actions and character reach back beyond one's control. If any of these affects moral assessment, then moral luck is real, and the "control principle" is false.

Historical Context

The puzzle is ancient. Aristotle, in the Nicomachean Ethics, distinguished voluntary from involuntary action and admitted that the involuntary can still be cause for pity and pardon — yet he also held that character, which shapes our voluntary actions, is itself formed by habituation over which we have limited control. The modern problem was created by Immanuel Kant, who made the control principle absolute: moral worth lies in the good will alone, which is fully under the agent's control, and nothing external can add to or subtract from it. Kant's position made luck a contaminant of morality by definition.

Williams and Nagel, writing in the 1970s, challenged this Kantian fortress from within the analytic tradition. Williams's essay recovered the Greek sense that a life can be blighted or blessed by fortune in ways that matter morally; Nagel's essay showed that the Kantian principle, taken strictly, leads to a view of moral assessment almost entirely disconnected from the lives we actually live. The problem has since become one of the most productive topics in ethics, generating a large literature on whether moral luck can be dissolved (by denying that we really assess luck), embraced (by giving up the control principle), or accommodated (by distinguishing kinds of moral assessment).

Key Arguments & Debates

The argument for the problem is an argument from cases: Williams's driver, Nagel's drunk driver, the Nazi-era bystander, and the genetically timid person all appear to be judged, in ordinary moral practice, for what is not under their control. The argument against it — the "denial of moral luck" — holds that these appearances are illusions: careful reflection shows that we do not, after all, judge the unlucky agent more harshly in the morally relevant sense; we only regret the outcome or feel sympathy. This is the position of Kantians and of philosophers such as David Lewis, who argued that we can coherently restrict moral assessment to what is in the agent's control.

The debate then turns on what "control" means. If control is understood the way the free will debate understands it — as requiring the ability to do otherwise, or ultimate sourcehood — then the Consequence Argument and the Manipulation Argument threaten the very possibility of control, and moral luck turns out to be a consequence of the more general problem of free will. Nagel himself drew this connection: "The area of genuine agency, and therefore of legitimate moral judgment, seems to shrink under this scrutiny to an extensionless point." Some philosophers, like Bernard Williams, accept the conclusion and recommend an ethics that gives up the aspiration to purity; others, like Nagel, are left with the paradox unresolved.

Contemporary Relevance

The problem of moral luck has become urgent in law, where outcomes routinely affect punishment: the drunk driver who kills is punished far more severely than the drunk driver who does not, although the difference is luck. Legal theorists debate whether this "result luck" in sentencing can be justified, and the philosophical debate directly informs criminal justice reform. In business ethics, executives are blamed for failed strategies that were indistinguishable in quality from successful ones; in medicine, doctors are judged for surgical outcomes affected by luck. The rise of AI adds a new dimension: when an autonomous system's decisions are determined by its training data and environment, questions of luck, control, and responsibility become central to deciding who — or what — is accountable for the harm a machine causes.

Related Concepts

• Moral Responsibility: the general framework the problem challenges.
• The Consequence Argument: the argument that control, in the deepest sense, may be impossible.
• Agent Causation: an attempt to restore genuine control over action.
• Frankfurt Cases: the debate over whether responsibility requires alternative possibilities.
• The Manipulation Argument: the challenge to control from external design.
• Free Will: the background issue behind the problem.

Further Learning

• Thomas Nagel, "Moral Luck," in Mortal Questions (1979).
• Bernard Williams, "Moral Luck," Proceedings of the Aristotelian Society (1976).
• Stanford Encyclopedia of Philosophy: Moral Luck