Incompatibilism

Incompatibilism is the thesis that free will is incompatible with determinism — that if every event (including every human choice) is necessitated by the past together with the laws of nature, then no one ever acts freely or is morally responsible in the desert-grounding sense. It is not, by itself, a view about whether we have free will, nor about whether determinism is true: it is a claim about an incompatibility. As such, incompatibilism is the genus under which several first-order positions fall, distinguished by what they go on to say about those further questions. This page treats incompatibilism in its own right — the master arguments that support it, its varieties, the replies it faces from compatibilists, and the misconceptions that surround it.

It is the direct denial of compatibilism, and it supplies the shared premise on which both libertarianism and hard determinism rest.

What incompatibilism claims (and what it does not)

Incompatibilism asserts a single conditional-strength claim:

Necessarily, if determinism is true, then no one has free will (in the sense required for moral responsibility).

Three clarifications fix its scope:

• It is neutral on the truth of determinism. An incompatibilist may think the world is determined (and conclude we are unfree) or undetermined (and hope we are free). The incompatibility itself is asserted either way.
• It is neutral on whether we have free will. That further question is what divides the species below.
• It targets the responsibility-relevant sense of freedom. Incompatibilists grant that there are weaker senses of "free" (uncoerced, unconstrained) that determinism leaves untouched; their claim is that these are not the sense that grounds basic desert, praise, and blame.

The whole dispute with compatibilism is therefore a disagreement about which freedom matters and what it requires — concentrated in two ideas the incompatibilist takes to be essential: leeway (genuinely open alternatives) and sourcehood (ultimate origination).

The two roads to incompatibilism

Incompatibilist arguments come in two broad families, corresponding to the two ingredients of freedom. A given incompatibilist may rely on one or both.

• Leeway incompatibilism — freedom requires the ability to do otherwise in a categorical sense: holding the entire actual past and the laws fixed, the agent could still have done something else. Determinism leaves exactly one possible future, so it removes leeway. The flagship argument here is the Consequence Argument.
• Source incompatibilism — freedom requires the agent to be the ultimate source or originator of the action: the buck must stop with the agent, not with causes tracing back before her birth. Determinism hands ultimate authorship to the remote past plus the laws, so it removes sourcehood. The flagship arguments here are the Origination/Ultimacy argument and the Manipulation arguments. This road is important because it survives even if Frankfurt cases succeed in showing responsibility does not require alternative possibilities — many contemporary incompatibilists are source incompatibilists for exactly this reason.

The Consequence Argument (leeway)

The most rigorous incompatibilist argument, developed by Carl Ginet, David Wiggins, and above all Peter van Inwagen (An Essay on Free Will, 1983). Its intuitive statement:

If determinism is true, then our acts are the consequences of the laws of nature and events in the remote past. But it is not up to us what went on before we were born, and neither is it up to us what the laws of nature are. Therefore the consequences of these things — including our present acts — are not up to us.

The force is that freedom is "transferred away" from us: we have no choice about the remote past $P_0$, no choice about the laws $L$, and (if determinism holds) no choice about the fact that $P_0\wedge L$ entails every present act — so we have no choice about our present acts. (The summary below gives the essentials; for the full formal treatment — the derivation, the agglomeration failure, Lewis's local-miracle reply, and the companion Mind argument — see the dedicated page on the Consequence Argument.)

The formal core

Van Inwagen regiments this with a modal operator $Np$ read "$p$, and no one has, or ever had, any choice about whether $p$." Two inference rules drive the argument:

$$\text{(α)}\frac{\square p}{Np}\text{(β)}\frac{Np,N(p\to q)}{Nq}$$

Rule (α): if $p$ is necessarily true, no one has a choice about it. Rule (β) — the crucial transfer of powerlessness — says: if no one has a choice about $p$, and no one has a choice about $p\to q$, then no one has a choice about $q$. Letting $P_0$ be the remote past, $L$ the laws, and $P$ a present act, determinism gives $\square ((P_0\wedge L)\to P)$; feeding the fixity of the past and laws through repeated application of (β) yields $NP$ — our acts are not up to us.

Compatibilist replies to the Consequence Argument

• Reject Rule (β). Thomas McKay and David Johnson (1996) showed (β) is invalid: it fails agglomeration (from $Np$ and $Nq$ one cannot in general infer $N(p\wedge q)$), and counterexamples involving probabilistic "no choice" cases break the rule. Van Inwagen's response is to seek a repaired principle; the dialectic continues.
• The local-miracle / conditional reply (Lewis). "Could have done otherwise" requires only that had the agent done otherwise, either the past or a law would have been (counterfactually) slightly different. To be able to act such that a law would have been broken is not the incredible power to break a law. The agent's ability is a "weak" ability, and that is all freedom needs.
• Deny the categorical reading of "can." Many compatibilists (dispositionalists such as Vihvelin, Fara) analyze "could have done otherwise" as a bundle of dispositions the agent retains in a determined world, dissolving the transfer argument's premise that the agent lacks the relevant ability.
• Concede leeway, save responsibility (semicompatibilism). Fischer grants the Consequence Argument's conclusion about alternatives but denies it touches responsibility, which rests on guidance control, not regulative control. This is why the source road below matters.

The Origination / Ultimacy argument (source)

Independently of alternatives, the incompatibilist presses: to be truly responsible for an action, one must be responsible for the sufficient causes of the action; in a determined world those causes trace back through one's character to heredity and environment one did not originate; so the regress of responsibility never terminates in the agent. Galen Strawson's "Basic Argument" is the sharpest form:

1. You do what you do, in any situation, because of the way you are.
2. To be ultimately responsible for what you do, you must be ultimately responsible for the way you are — at least in relevant respects.
3. But to be ultimately responsible for the way you are, you would have had to bring it about that you are that way — and to do that on the basis of some prior way you already were, regressing infinitely.
4. Such ultimate self-creation (being causa sui) is impossible.
5. Therefore ultimate responsibility is impossible.

Note the sting in the tail: Strawson's argument is more radical than standard incompatibilism, because it concludes that no one is ultimately responsible whether determinism is true or not — indeterminism cannot supply self-creation either. Source incompatibilists who stop short of this (e.g. Kane) argue that ultimacy requires only a finite history of undetermined self-forming actions, not literal causa sui — the move that keeps libertarianism alive against the Basic Argument.

The Manipulation arguments (source)

The most persuasive intuitive engine of source incompatibilism. The strategy: exhibit an agent who is covertly manipulated into satisfying every condition compatibilists offer for free, responsible action, yet who intuitively is not responsible — then argue there is no relevant difference between this agent and any ordinary determined agent.

• Pereboom's four-case argument. Professor Plum murders White. In Case 1 he is created moments before by neuroscientists who directly manipulate his brain in real time; in Case 2 he is programmed at the start of life; in Case 3 he is rigorously trained by his community; in Case 4 he is simply an ordinary agent in a normal deterministic universe. At each step the manipulation becomes less direct, but — Pereboom argues — there is no principled difference in responsibility between adjacent cases. Since Plum is plainly not responsible in Case 1, and nothing relevant changes down the line, he is not responsible in Case 4 either. Hence ordinary determinism defeats responsibility.
• Mele's Zygote Argument. The goddess Diana creates a zygote, Ernie, designing it precisely so that, given the actual laws and world, Ernie will perform a particular murder thirty years later. Ernie satisfies every compatibilist condition (reasons-responsiveness, mesh, real-self expression) — yet seems a mere instrument of Diana's design. And there is no relevant difference between Ernie's deterministic causal history and that of any ordinary determined agent; so if Ernie is not responsible, neither is anyone in a determined world.

Compatibilist replies to manipulation

• Hard-line reply (McKenna): bite the bullet — the manipulated agent is responsible (or our contrary intuition is an unreliable artifact of the spooky manipulator). If the compatibilist conditions are genuinely met, that just is what responsibility consists in.
• Soft-line reply (Fischer, Mele, Haji): identify a relevant difference — typically a historical / ownership condition that manipulation violates and ordinary determinism does not. The manipulated agent's deliberative mechanism was installed by bypassing her own prior agency; ordinary agents acquire theirs through a normal developmental history in which they "take responsibility" for their mechanism over time. (Incompatibilists rejoin that any such history is itself just a longer deterministic chain the agent didn't originate, so the difference is not responsibility-relevant.)

The varieties of incompatibilism

Once the incompatibility is granted, three positions diverge on the further questions:

• Hard determinism (the classical "no-free-will" position — d'Holbach, Spinoza read deterministically, Clarence Darrow in forensic practice) accepts both incompatibilism and the truth of determinism, and bites the bullet: no one is ever truly responsible.
• Hard incompatibilism (Derk Pereboom, Living Without Free Will; Galen Strawson) is the modern refinement: it does not need determinism to be true. It argues freedom is incompatible with determinism (via the above) and that indeterminism would only add luck (the objection that haunts libertarianism) — so on every hypothesis about the causal order, desert-grounding free will is absent. This is free-will skepticism, and it typically pairs with a forward-looking reconstruction of moral life (protection, reconciliation, moral formation) that abandons basic desert while keeping much else.

What unites all three against compatibilism is the conviction that the freedom worth wanting requires either categorical leeway or ultimate sourcehood — something determinism cannot supply.

A short history

• Ancient roots. The Epicureans held determinism (Democritean atomic necessity) incompatible with agency and posited the atomic swerve to escape it — an early libertarian incompatibilism. The Stoic–Epicurean debate over fate is the origin of the whole dispute.
• Medieval. Worries about divine foreknowledge (if God infallibly knows tomorrow's act, is it not already fixed?) are a theological incompatibilism, addressed by Boethius, Aquinas, and Ockham.
• Early modern. d'Holbach (System of Nature, 1770) gives the canonical hard determinist statement: man is "a being purely physical," a link in nature's chain, and free will an illusion. Kant, by contrast, is an incompatibilist who rescues freedom transcendentally, placing it in the noumenal self outside the deterministic phenomenal order.
• William James (1884) coins "hard" and "soft" determinism, and frames the dilemma of determinism that organizes the modern debate.
• C. D. Broad (1934) sharpens the "could have done otherwise" analysis that the Consequence Argument later formalizes.
• Roderick Chisholm (1964) revives agent-causal libertarian incompatibilism.
• Peter van Inwagen (1983) gives incompatibilism its rigorous modern form in the Consequence Argument, making incompatibilism respectable as a conclusion of argument rather than a mere intuition.
• Galen Strawson (1986, 1994) presses the Basic Argument for the impossibility of ultimate responsibility.
• Derk Pereboom (2001, 2014) and Saul Smilansky, Bruce Waller, Gregg Caruso develop contemporary hard incompatibilism / free-will skepticism and its practical implications (notably for retributive punishment).

Arguments for incompatibilism (summary)

1. The Consequence Argument — freedom requires leeway; determinism, via the fixity of the past and laws and the transfer principle (β), removes it.
2. The Origination/Ultimacy argument — responsibility requires ultimate sourcehood; a determined causal chain locates the ultimate source in the remote past, never in the agent.
3. The Manipulation/Zygote arguments — a covertly determined agent who meets all compatibilist conditions is intuitively not responsible, and there is no relevant difference between such an agent and any determined agent.
4. The intuition of openness — deliberation presents the future as genuinely open and the choice as up to us now; incompatibilists take this categorical openness, which determinism contradicts, to be a datum compatibilism cannot honor.

Objections to incompatibilism (and replies)

• The conditional-analysis / dispositional objection. Compatibilists argue "could have done otherwise" is best read hypothetically or dispositionally, so determinism does not remove the relevant ability. Incompatibilist reply: the hypothetical reading captures only a weak ability and smuggles an unanalyzed "ability to choose otherwise" into its antecedent; it does not deliver the categorical openness freedom requires (the Chisholm/Austin point).
• Frankfurt cases against leeway. If responsibility does not require alternative possibilities (PAP is false), the Consequence Argument's leeway requirement is moot. Incompatibilist reply: retreat to source incompatibilism, which never needed PAP — Frankfurt cases at most refute the leeway road, leaving the origination and manipulation arguments untouched. (Plus the "flicker of freedom" and Kane–Widerker dilemma replies that question whether Frankfurt cases work in a genuinely indeterministic setting.)
• The "verbal dispute" charge (Hume). The whole disagreement is merely about how to define "free." Incompatibilist reply: it is substantive, not verbal — it concerns whether basic desert (the fairness of blame and punishment) is genuinely secured by a chain the agent did not originate. That is a real question with real stakes (punishment, the reactive attitudes), not a choice of words.
• The pragmatic / Strawsonian objection. The reactive-attitude practice is not, and need not be, hostage to any metaphysical thesis; demanding ultimacy is a philosopher's overreach. Incompatibilist reply (Pereboom, Waller): we can and arguably should revise the practice — abandoning basic desert and retributive punishment while keeping forward-looking forms of moral concern; the practice's mere entrenchment does not show it is justified.
• The self-refutation / "you can't help believing it" objection. Incompatibilist reply: the psychological inevitability of feeling free is precisely what a determinist would predict, and says nothing about whether the feeling is veridical.

Common misconceptions

• "Incompatibilism says we have no free will." No — incompatibilism is only the incompatibility claim. The libertarian is an incompatibilist who affirms free will. Denying free will is the further step taken by hard determinists and hard incompatibilists.
• "Incompatibilism says determinism is true." It is neutral on that. Some incompatibilists (libertarians) deny determinism precisely because they accept the incompatibility and affirm freedom.
• "Incompatibilism is the same as fatalism." No — like determinism, incompatibilism does not say outcomes occur regardless of your choices; it says that if your choices are determined, they are not up to you in the freedom-grounding sense. Deliberation can still be causally efficacious (see the introduction).
• "Incompatibilism requires belief in a soul or agent-causation." Only some libertarian versions invoke agent-causation. Hard determinists and hard incompatibilists are typically thoroughgoing naturalists; the Consequence and Basic Arguments make no supernatural assumptions.
• "The Consequence Argument has been refuted." It is contested — (β) and the local-miracle reply are live disputes — but it remains the central reason incompatibilism is taken seriously, and source incompatibilism does not depend on it at all.
• "Incompatibilists must think no one should ever be blamed or punished." Only the skeptical species draw that conclusion, and even they typically endorse forward-looking (deterrence, protection, reform) rather than retributive justification — they reject basic desert, not all social response.

Where incompatibilism sits

Against the master dilemma, incompatibilism is the affirmation of premise (3) — free will is incompatible with determinism — which compatibilism denies. It leaves premises (1) free will exists and (2) determinism is true open, and the way a given incompatibilist settles them fixes whether they end up a libertarian (keep 1, drop 2), a hard determinist (keep 2, drop 1), or a hard incompatibilist (drop 1 on grounds that hold whatever the status of 2). Its strength is the intuitive grip of the leeway and sourcehood requirements — the sense that a choice fixed before one's birth is not, in the deepest sense, one's own. Its burden is to show those requirements are genuine conditions on responsibility rather than an inflated, perhaps incoherent, demand for causa sui — exactly the charge the compatibilist presses in reply.

The next pages take up hard incompatibilism / free-will skepticism as a position in its own right, and the bearing of physics and quantum mechanics on whether the indeterminism the libertarian incompatibilist needs is real and usable.