What Is Compatibilism?

Direct Answer

Compatibilism is the view that free will is compatible with determinism — that we can be genuinely free and morally responsible even if every event, including our choices, is fully determined by prior causes. The hard determinist holds that if determinism is true, free will is an illusion; the libertarian holds that free will is real and determinism must therefore be false. The compatibilist rejects both: the truth of determinism would not rob us of freedom, because freedom does not require the absence of causation.

The compatibilist strategy is to give an account of what "free" actually means in ordinary life. When we say someone acted freely, we typically mean they were not coerced, compelled, manipulated, or constrained — they acted on their own desires and beliefs, in the absence of external interference. A person who chooses a meal from a menu is free; a person whose arm is forcibly moved is not. On this account, freedom is opposed to constraint, not to causation. A determined agent whose actions flow from her own character, desires, and deliberations is free, because the causal story runs through her.

The classic formulation belongs to Hume, who wrote in the Enquiry Concerning Human Understanding that liberty is "a power of acting or not acting, according to the determinations of the will." The opposite of liberty, Hume insisted, is not necessity but constraint: "the most perfect philosophy" is compatibilist, because it reconciles the universality of causation with the commonsense fact that we act freely when nothing blocks us. Contemporary defenders have refined the view. Daniel Dennett argues in Elbow Room and Freedom Evolves that freedom is a real, evolved capacity of creatures who can reflect, learn, and respond to reasons — not a mysterious exemption from physics.

The most influential modern refinement is the hierarchical account, associated with Harry Frankfurt. A person is free, on this view, when she identifies with the desires that move her to act — when her will is, at a higher level, what she wants it to be. This account is designed to handle cases where the ability to do otherwise seems irrelevant. Frankfurt's famous "counterexamples" show that a person can be morally responsible for an act she could not have avoided doing, provided she did it for her own reasons. If responsibility does not require alternative possibilities, then determinism — which removes alternative possibilities — does not threaten responsibility after all.

Historical Context

Compatibilism is the oldest and most durable answer to the problem of free will. Its modern form begins with Thomas Hobbes, who argued in Leviathan (1651) that freedom is the absence of external impediment — a determined will is still a will, and a person acts freely whenever she acts as she wills. Hume and John Stuart Mill developed the position in the eighteenth and nineteenth centuries, insisting that the debate turns on a confusion between "necessity" and "constraint." In the twentieth century, Frankfurt's 1969 paper "Alternate Possibilities and Moral Responsibility" redirected the debate toward responsibility, and the "reasons-responsive" theories of contemporary philosophers such as John Martin Fischer and Mark Ravizza have made compatibilism the majority position among working philosophers. Dennett's books brought the view to a wider audience, while critics from both sides — hard determinists like Sam Harris and libertarians — continue to press the objection that the compatibilist's "free will" is not the real thing people care about.

Philosophical Significance

Compatibilism matters because it promises to reconcile the scientific picture of the world with our moral lives. If compatibilism is true, then the discovery that our decisions have neural causes does not undermine responsibility, desert, or the practice of holding people accountable. Courts, moral praise and blame, and the very idea of character all presuppose that people can be responsible for what they do; compatibilism shows how that presupposition survives determinism.

The stakes are practical as well as theoretical. As neuroscience advances, claims that "science shows free will is an illusion" have become common. Compatibilists respond that such claims rest on a mistaken equation of freedom with indeterminism: the fact that our choices are caused no more shows that we are unfree than the fact that our digestion is caused shows that we do not eat. What would undermine freedom, on the compatibilist account, is manipulation, compulsion, or insanity — not causation. The debate thereby connects to ethics, to the philosophy of action, and to how we should think about the self and personal identity.

Examples & Thought Experiments

The locked room example illustrates the core distinction. You are in a room and choose to stay because you want to — you are free. You are in the same room, but the door is locked and you cannot leave — you are unfree. The difference has nothing to do with whether your choice was caused; it has to do with whether you could act on your will. Compatibilists argue that determinism is like the first case: it causes your choices, but it does not imprison them.

Frankfurt cases make the same point about responsibility. Imagine an agent who is about to decide on his own to do something, while a manipulator stands ready to force him if he shows any sign of deciding otherwise. The agent decides on his own; the manipulator never intervenes. The agent could not have done otherwise — the manipulator would have prevented it — yet he is clearly responsible, because he acted for his own reasons. If responsibility does not require alternative possibilities, determinism poses no threat to it.

The addiction example tests the hierarchical account. An unwilling addict hates his addiction and struggles against it — his desire to use is not endorsed at a higher level, and he is not free. A willing addict wholeheartedly embraces his habit — his will is his own, and on the hierarchical account he acts freely. The example shows how compatibilism locates freedom in the structure of the agent's own will, not in the absence of causes.

Related Concepts

• Free will and determinism vs. free will
• Philosophy of action and ethics
• Consciousness and decision-making
• The self and personal identity
• Stoicism and pragmatism — traditions with compatibilist sympathies
• Thinking, Fast and Slow — the psychology of decision

Further Learning

• Stanford Encyclopedia of Philosophy, Free Will
• Stanford Encyclopedia of Philosophy, Compatibilism
• Internet Encyclopedia of Philosophy, Free Will