What Is Compatibilism as a Philosophical Doctrine

Compatibilism is the doctrine that free will and determinism are compatible: that a person can act freely even if every event — including every human action — is causally determined. The compatibilist denies that freedom requires the absence of causation. Freedom, on this view, is not the power to act without causes; it is the absence of certain kinds of constraints — coercion, compulsion, ignorance, madness. A free action is one that flows from the agent's own desires, deliberation, and character, in the normal way, without external interference. Since determined actions can be exactly that, determinism poses no threat to freedom.

The doctrine is sometimes called "soft determinism," to mark the position that accepts determinism but rejects hard determinism's conclusion that freedom is an illusion. It is the majority position in the contemporary free will debate, and it has an ancient pedigree: the Stoics defended a version of it, arguing that freedom consists in assenting to the determinations of fate. Its modern form was fixed by Hume, refined by Kant in a distinctive transcendental key, and given a naturalistic formulation by Daniel Dennett in our own time.

Historical Background

Compatibilism enters the modern debate with Hobbes and Locke, but its classic formulation is Hume's. In A Treatise of Human Nature and the Enquiry Concerning Human Understanding, Hume argued that the "dispute" about liberty and necessity is merely verbal, the product of a confused definition of freedom. Liberty, properly understood, "is only the power of acting or not acting, according to the determinations of the will": a person is free when nothing prevents them from doing what they will to do. This is perfectly compatible with the will itself being caused — with "necessity," understood as the constant conjunction of motives and actions. "By liberty, then, we can only mean a power of acting or not acting, according to the determinations of the will; that is, if we choose to remain at rest, we may; if we choose to move, we also may." The compatibilist freedom that matters, Hume insisted, is the freedom of action from external constraint, not the freedom of will from causation.

Kant's relation to compatibilism is more complex. In the Critique of Pure Reason, he argued that the empirical world is deterministic — every event has a cause — and that freedom, in the sense of an uncaused first beginning, is impossible within it. Yet he insisted that we must think of ourselves as free: morality presupposes that we can act from duty, that "ought" implies "can." His solution is transcendental idealism: as appearances, our actions are fully determined; as things in themselves, we may be free. Whether this is a version of compatibilism or a distinct third position is debated, but Kant bequeathed to the tradition the crucial idea that the freedom that matters for morality is not the freedom to act uncaused but the freedom of rational self-governance.

The twentieth century produced a rich crop of compatibilist theories. The "hierarchical" theory of Harry Frankfurt holds that a person acts freely when their first-order desires are endorsed by second-order desires — when we want to want what we want. The "reasons-responsive" theory, associated with John Martin Fischer and Mark Ravizza, holds that freedom and responsibility require only that the agent's mechanism of action be responsive to reasons. And Daniel Dennett, in Elbow Room and Freedom Evolves, argues that free will is an evolved biological capacity for self-control, deliberation, and the avoidance of harmful outcomes — a real capacity that requires no metaphysical magic and is fully compatible with the causal order.

Key Arguments

The Argument from the Meaning of Freedom

The core compatibilist argument is conceptual. When we say that a person acted freely, we mean, in ordinary life, that they were not coerced, compelled, or deceived — that they did what they wanted to do, for reasons of their own. Nobody, in asking whether a defendant acted freely, is asking whether their action had causes. The determinist threat is therefore based on a confusion: it redefines freedom as the absence of causation and then observes, correctly, that causation is everywhere. But freedom in the sense that matters — the sense involved in deliberation, choice, and responsibility — is not the absence of causation; it is the absence of constraint. Since determinism does not imply constraint, determinism does not threaten freedom.

The Argument from the Point of Deliberation

A second argument appeals to the practical point of deliberation and choice. When we deliberate, we do not ask "is my choice caused?" — we ask "which option is best?" Deliberation is compatible with the deliberator's belief that their choice will be caused by the deliberation; indeed, deliberation would be pointless if it were not effective, and it is effective precisely by causing the choice. The libertarian demand that deliberation presuppose an uncaused choice is, the compatibilist argues, both psychologically false and practically unintelligible. We deliberate exactly because our choices are sensitive to our reasons — and that sensitivity is a causal sensitivity, not an absence of causation.

The Argument from Moral Responsibility

The most powerful argument for compatibilism is ethical. If determinism ruled out responsibility, then no one would ever deserve praise or blame, and our practices of holding people responsible — rewarding, punishing, thanking, resenting — would rest on an illusion. The compatibilist argues that this conclusion is both unacceptable and unnecessary. Responsibility tracks the agent's control: whether the action flowed from the agent's own character, reasons, and decision, in the absence of constraint. A determined agent can be fully in control in this sense, and so can be fully responsible. What responsibility does not require is the libertarian's "contra-causal freedom" — and the burden of proof is on those who claim we need it.

Contemporary Relevance

Compatibilism is the default position in contemporary philosophy. Most philosophers of action, most moral philosophers, and most philosophers of mind accept that free will is compatible with determinism; the live debates concern the form of compatibilism — whether it requires hierarchical endorsement, reasons-responsiveness, or something else — and whether it can answer the challenges raised by neuroscience. The empirical sciences have only strengthened the compatibilist case in one respect: as evidence accumulates that our choices are shaped by neural processes, genes, and environments, the compatibilist's insistence that freedom is not the absence of causation has become more, not less, important. If freedom were the absence of causation, the sciences would have refuted it long ago; because freedom is the absence of constraint, the sciences have not touched it.

Sources

• Stanford Encyclopedia of Philosophy, "Compatibilism"
• Stanford Encyclopedia of Philosophy, "Free Will"
• Internet Encyclopedia of Philosophy, "Hume on Free Will"
• Internet Encyclopedia of Philosophy, "Free Will"

Related Topics

• What is compatibilism? — the answer page for the doctrine
• What is determinism? — the thesis compatibilism reconciles with freedom
• Determinism — the doctrine compatibilism accepts
• Indeterminism — the doctrine compatibilism rejects as unnecessary
• Free will — the concept at issue
• Moral responsibility — the ethical stake of the debate
• Philosophy of action — the branch in which the doctrine is developed