What Is the Consequence Argument?

Direct Answer

The Consequence Argument is the most influential formal argument for incompatibilism — the thesis that free will cannot coexist with determinism. Its most famous formulation is due to Peter van Inwagen, who stated it in An Essay on Free Will (1983): if determinism is true, then our acts are the consequences of the laws of nature and events in the remote past. But we have no power over what went on before we were born, and no power over the laws of nature. Therefore we have no power over the consequences of those things — including our present acts. Since a person acts freely only if she could have done otherwise, and the Consequence Argument shows that nobody could ever have done otherwise under determinism, determinism rules out free will.

The argument's engine is a transfer principle: if a person has no power over a proposition p, and no power over the fact that p entails q, then she has no power over q. Powerlessness transfers across entailment. Let p be the state of the universe in the distant past, L the laws of nature, and q your action. Determinism says that the conjunction of p and L entails q. Since you have no power over p or L, and the entailment itself is not up to you, you have no power over q. You cannot do otherwise.

An example brings the point home. Suppose a student is studying for an exam and decides to continue studying rather than go to a party. The compatibilist says she is free: nothing forced her hand. The Consequence Argument replies that her decision was entailed by the state of the universe a billion years ago together with the laws of nature. Since she cannot reach back and change either, the outcome — the decision to study — was never genuinely open to her. The experience of open alternatives, the argument concludes, is an artifact of ignorance.

Historical Context

The intuition behind the Consequence Argument is ancient. It is already present in the Stoics' debates about fate and in the medieval puzzle of whether human freedom can survive divine foreknowledge. The early moderns gave it mechanical form: if the world is a clockwork and we are parts of it, our choices are determined by prior states. What was missing until the twentieth century was a rigorous statement of the logic. Van Inwagen supplied it in 1983, and his formalization transformed the debate: instead of trading intuitions about "could have done otherwise," philosophers could now examine a precise argument with identifiable premises and a transfer principle open to scrutiny.

The argument immediately displaced earlier incompatibilist appeals. It also reorganized the landscape: libertarians (who deny determinism) and hard determinists (who accept determinism but reject free will) both embrace the Consequence Argument, while compatibilists are defined by their attempt to find the flaw in it. Its rise is part of the broader professionalization of the free will debate in the analytic tradition of the late twentieth century.

Key Arguments & Debates

The argument's strength lies in the plausibility of its premises: nobody thinks we control the distant past, and the laws of nature are equally beyond our power. The transfer principle is the obvious target. Compatibilists such as Daniel Dennett and the philosopher David Lewis attacked it: Lewis famously argued that we can have power over a consequence without having power over its causes, because power is not closed under entailment in the way the principle requires. The reply runs through possible worlds: the student could have done otherwise in the sense that there is a possible world with the same laws where, with slightly different prior events, she goes to the party. But this, incompatibilists object, concedes the point — the "could" is a bare modal notion that has nothing to do with the agent's control.

A second line of reply, associated with compatibilist theories of "conditional analysis," interprets "could have done otherwise" as "would have done otherwise if she had chosen to": the student could have gone to the party in the sense that she would have, had she wanted to. Van Inwagen argues that this changes the subject: the question is whether she could have chosen otherwise, not whether her choice would have differed had it differed. The debate thus concentrates on what "can" and "power" mean when applied to agents — a conceptual dispute that the Consequence Argument forces into the open.

Contemporary Relevance

The Consequence Argument has direct bearing on how we read the science of decision. If the argument is sound, then the neuroscientific finding that brain events cause behavior is not merely a challenge to free will — it is a proof of its impossibility under determinism, and the only escape routes are indeterminism or a reinterpretation of "free." This is why the neuroscience debate often circles back to physics: some libertarians appeal to quantum indeterminism at the neural scale to open the window the argument closes. The argument also shapes legal and ethical thinking about "could have done otherwise" in criminal law, where the phrase is a fixture of commonsense jurisprudence: if the Consequence Argument is right, the law's implicit picture of agency is in tension with the scientific image of a determined brain. It thus remains the theoretical hinge on which the modern free will debate turns.

Related Concepts

• Libertarianism: the position that accepts the argument and denies determinism.
• Hard Determinism: the position that accepts the argument and denies free will.
• Compatibilism: the position that finds a flaw in the argument.
• The Manipulation Argument: a sibling argument against compatibilism.
• Free Will: the concept at stake.
• Free Will vs. Determinism: the wider debate.

Further Learning

• Peter van Inwagen, An Essay on Free Will (1983).
• Stanford Encyclopedia of Philosophy: Arguments for Incompatibilism
• Stanford Encyclopedia of Philosophy: Causal Determinism