What Is Libertarianism?

Direct Answer

Libertarianism is the theory of free will that joins two theses: incompatibilism — the claim that free will cannot coexist with determinism — and the claim that determinism is false. On the libertarian view, free will is not merely the ability to act on one's desires without external constraint. It requires the ability to do otherwise: in a given situation, with the past and the laws of nature held fixed, a genuinely free agent could have chosen a different course of action. The contrast is with compatibilism, which holds that freedom is compatible with determinism because what matters is not the absence of causes but the absence of compulsion.

The key distinction inside libertarianism is between two ways of supplying the required indeterminism. Event-causal libertarianism, defended by Robert Kane, locates freedom in indeterministic events within the agent: when we face genuinely difficult choices, the neural processes involved are undetermined, and which option prevails is not fixed by prior causes. The agent's decision is still caused by her character, reasons, and efforts — but indeterministically. Agent-causal libertarianism, defended by Roderick Chisholm and Thomas Reid, goes further: the agent herself, a persisting substance, causes her decisions without being caused to do so. The self is an uncaused cause, a source of activity that cannot be reduced to events in the brain.

An example clarifies the difference. Suppose a struggling writer is offered a large bribe to abandon her principles. A compatibilist says she is free if nothing physically forces her hand. A libertarian says she is free only if, the past and laws being what they are, she genuinely could have taken the bribe. An event-causal libertarian adds that her deliberative process may itself have been genuinely undetermined; an agent-causal libertarian adds that she — the person — was the origin of the choice in a way no series of events could capture.

Historical Context

The deep roots of libertarian thinking lie in theology: the medieval debate over whether divine foreknowledge could coexist with human freedom shaped the conviction that moral responsibility requires a will not fixed by prior causes. In the modern period, Immanuel Kant gave libertarianism its most influential philosophical form, arguing in the Critique of Pure Reason that while all appearances are causally determined, the rational agent can be thought of as acting from a free causality of reason — a spontaneity that begins a causal series from itself. Kant's "transcendental freedom" was the price he paid to save morality.

The term "libertarianism" was popularized by William James, whose 1884 essay "The Dilemma of Determinism" defended the view that genuine alternatives — what he called "possibilities" that are real in advance — are required for regret and moral judgment to make sense. In the twentieth century the debate became technical. Peter van Inwagen's Consequence Argument sharpened the incompatibilist case, while Robert Kane, Carl Ginet, and Randolph Clarke developed sophisticated libertarian theories that tried to answer the objection that indeterminism undermines rather than grounds control.

Key Arguments & Debates

The central argument for libertarianism is the requirement of alternative possibilities: moral responsibility seems to presuppose that the agent could have done otherwise, and determinism — which makes the past and laws entail every action — would eliminate that possibility. The Consequence Argument formalizes this: if determinism is true, our acts are the consequences of laws and the distant past, and we have no power over either, so we have no power over our acts. If free will is real, libertarians conclude, determinism must be false.

The central objection is the luck problem. Suppose an indeterministic process precedes a choice between A and B, and the agent chooses A. Given the same past and laws, B was also possible — but then what explains the difference? If nothing explains it, the choice looks like a matter of luck, and luck seems no better for freedom than determinism. Event-causal libertarians answer with "plural responsiveness": the agent's reasons and character still shape the odds, and the agent is responsible for the character and reasons through earlier free choices ("ultimate responsibility"). Agent-causal libertarians answer differently: the agent's substance-causal power explains the choice without being explained by anything else. Critics like Galen Strawson and Daniel Dennett charge that the first answer collapses into chance and the second into mystery.

Contemporary Relevance

Neuroscience intensifies the pressure. Benjamin Libet's readiness-potential experiments showed that a measurable brain signal precedes the conscious intention to act by hundreds of milliseconds, which many take to mean that decisions are settled before we are aware of choosing. Subsequent fMRI studies have predicted simple choices seconds before subjects report deciding. Defenders of libertarianism respond that these experiments test trivial movements, not the self-reflective deliberation in which free will is supposed to reside, and that neural prediction does not by itself show the absence of agent-level control. The same indeterminism libertarians need may also be supplied by quantum randomness amplified at the neural scale, though critics note that random noise is not agency. The debate now turns on whether a scientifically respectable account can make the agent, rather than chance or fate, the true origin of action.

Related Concepts

• Free Will: the general question of which this theory is one answer.
• Compatibilism: the rival view that freedom is compatible with determinism.
• Hard Determinism: the rival incompatibilist view that determinism is true and freedom is an illusion.
• Agent Causation: the substance-causal version of libertarianism.
• The Consequence Argument: the formal case for incompatibilism.
• Free Will vs. Determinism: the broader debate in context.

Further Learning

• Stanford Encyclopedia of Philosophy: Incompatibilist (Nondeterministic) Theories of Free Will
• Internet Encyclopedia of Philosophy: Free Will
• Robert Kane, The Significance of Free Will (1996).
• William James, "The Dilemma of Determinism," in The Will to Believe (1897).