What Is Libertarian Free Will? Genuine Alternatives and Self-Forming Actions

Direct Answer

Libertarian free will is the view that free will is real and that it requires genuine alternative possibilities: at the moment of choice, the agent could have done otherwise. Because determinism entails that only one future is possible, libertarianism is a form of incompatibilism — it holds that free will and determinism cannot both be true, and that since we are free, determinism is false.

The libertarian does not merely deny determinism; she must say something positive about how free choices are made. Two families of answers dominate. Event-causal libertarianism holds that free actions are caused by the agent's reasons and efforts in a way that is not fully determined — the "self-forming action" of Robert Kane. Agent-causal libertarianism holds that the person herself, as a substance, causes her free actions without being caused to do so — the view of Thomas Reid and Roderick Chisholm.

Historical Context

Libertarian intuitions are among the oldest in philosophy. Aristotle's discussion of the voluntary, the "origin of action," and what is "up to us" already gestures at genuine alternatives. In the Christian tradition, the defense of human freedom against divine foreknowledge and predestination repeatedly took libertarian form: if God holds us responsible, our choices must be genuinely ours.

Kant gave libertarianism its most influential modern defense. Because morality presupposes that "ought implies can," and because moral duties bind unconditionally, the agent must be able to choose the moral law freely — a freedom Kant located in the noumenal, rational self beyond the causal order of appearances. William James defended a pragmatist libertarianism in "The Dilemma of Determinism": the difference between a deterministic and an open world is a real difference in the moral texture of experience, and only the open world makes regret, effort, and moral struggle meaningful. In the late twentieth century, Robert Kane's event-causal theory and Randolph Clarke's agent-causal theory brought libertarianism to a new level of analytical rigor.

Key Concepts

Alternative possibilities. The condition that the agent could have done otherwise, holding fixed the past and the laws. Libertarians treat this as necessary for free will; the principle of alternate possibilities extends it to moral responsibility.

Indeterminism. The denial of determinism: more than one future is consistent with the past and the laws. Libertarianism requires indeterminism at least at the moment of free choice.

Self-forming action (SFA). Kane's term for a choice made under inner conflict where the outcome is not determined by prior states — the agent's effort "forms the self" that later acts.

Agent causation. The claim that a person, not merely an event, can be a cause: free actions originate in the agent as an uncaused cause.

Sourcehood vs. alternatives. Modern libertarians increasingly emphasize that freedom requires being the ultimate source of one's action, not merely facing open alternatives; "source" libertarianism combines both.

Philosophical Perspectives

Event-causal libertarianism confronts the "luck objection": if the outcome of deliberation is undetermined, then the difference between choosing A and choosing B seems to be a matter of luck, and luck is not authorship. Kane responds that in a self-forming action, the agent does both courses of action at once — he tries both, and the effort itself is what determines the outcome; the agent is responsible because the choice is a product of his character, reasons, and effort over time.

Agent-causal libertarianism avoids the luck objection by positing the agent as a cause that is not itself an event: the person settles the matter. Critics object that substance causation is mysterious — a primitive "power of a person" that science has no place for. Proponents reply that we experience ourselves as agents directly, and that a naturalistic philosophy that cannot accommodate this experience is impoverished.

Both versions draw on physics. Quantum mechanics suggests that nature at the microlevel is irreducibly chancy, which shows that determinism is not forced on us by science. Libertarians add that genuinely open neural processes could implement open choice — though they concede that "could" is a long way from "does," and that identifying such processes remains an open research program.

Modern Reflection

Libertarianism remains a minority position in academic philosophy, yet its core intuition is widely shared: most people believe that they could have done otherwise and that this matters for responsibility. Experimental philosophy has documented this "folk libertarianism," and philosophers debate whether it reflects a truth about agency or a comforting illusion.

The scientific pressure on libertarianism comes from two directions. First, neuroscience suggests that decisions are shaped by unconscious brain activity that precedes awareness, narrowing the window in which an "undetermined self" could act. Second, the burden of showing where indeterminism enters the causal chain of deliberation is heavy. Libertarians respond that neither result shows determinism, and that the experience of open choice is among the most reliable facts we have. As Kant insisted, practical life forces us to regard ourselves as free agents, whatever metaphysics says.

Related Thinkers

• Kant — freedom as a postulate of the moral law
• William James — "The Dilemma of Determinism" and pragmatic freedom
• Daniel Dennett — the leading compatibilist critic of libertarianism
• Jean-Paul Sartre — radical freedom beyond character and situation

Related Quotes

• "Our first act of freedom is to choose our beliefs about freedom." — paraphrase of William James
• "Ought implies can: because we are bound by the moral law, we must be free." — Kant, Critique of Practical Reason
• "Man is condemned to be free." — Jean-Paul Sartre, Existentialism Is a Humanism

Sources

• Incompatibilism (Theories) — Stanford Encyclopedia of Philosophy
• Agency — Stanford Encyclopedia of Philosophy
• The Significance of Free Will — Robert Kane, Oxford University Press
• The Will to Believe — William James (contains "The Dilemma of Determinism")

Further Learning

• Continue with What Is Free Will? and What Is Compatibilism?
• Study the Free Will topic and the Understanding Reality collection
• Read about metaphysics and the philosophy of action