Concept

Compatibilism

Intro

Here is the puzzle. Either every event in the world is determined by prior causes (genes, brain chemistry, upbringing, the laws of physics, in the Reformed Christian version, God's eternal decree) or some events are not. If every event is determined, including your "choice" to read this paragraph, in what sense are you really choosing? You could not have done otherwise. So how can you be morally responsible for anything?

There are three main answers in Christian and philosophical discussion.

Hard determinism says: everything is determined, free will is an illusion, and moral responsibility collapses with it. Sam Harris in Free Will (2012) defends this view from a secular angle.

Libertarian free will says: real choice requires the genuine ability to do otherwise, the future is not closed, and human agents are not fully determined. Most Arminian and Catholic thinkers hold some version of this.

Compatibilism takes the third path. It accepts that actions are causally determined and also accepts that we are free and responsible. The trick is in what free means. The compatibilist says: an action is free when it flows from your own desires, beliefs, and character without external coercion, even if those desires were themselves shaped by prior causes. The bank robber whose desires were shaped by his upbringing still robs the bank because he wants to and is responsible for the choice. The Christian convert whose desires were transformed by the Holy Spirit still trusts Christ because he wants to and is genuinely choosing. Freedom is doing what you want, not having uncaused wants.

That sounds suspicious to many people. It can feel like a verbal trick, "we just redefined the word free until it means whatever fits determinism." But the position has serious arguments behind it. Frankfurt's famous 1969 thought experiment shows that we hold people responsible even when, on close inspection, they could not have done otherwise. And it fits a lot of biblical material: Joseph's brothers freely sold him into slavery, and yet God meant it for good (Genesis 50:20); Judas freely betrayed Jesus, and yet his betrayal was part of God's set plan (Acts 2:23).

Compatibilism is the standard Reformed view (Jonathan Edwards is the great American defender, Freedom of the Will, 1754), the standard secular view in contemporary philosophy of mind, and the position that lets you hold both God's exhaustive sovereignty and real human responsibility without watering down either. The page below walks the position's machinery, the Frankfurt cases, the hierarchical and reasons-responsiveness models, the contrast with libertarian free will, and the major Christian objections.

In full

The position that free will is compatible with determinism, that an action can be both causally determined (by prior states, including divine decree, neural events, character, or circumstances) and free in the sense relevant to moral responsibility. The compatibilist redefines or refines free will so that its core requirement is the agent's acting from his own desires, beliefs, and character without external coercion, rather than the libertarian requirement of the genuine ability to do otherwise. Compatibilism is the standard secular position in contemporary philosophy of mind and the standard Reformed / Edwardsian theological position, sitting between Hard Determinism (which denies free will) and Libertarian Free Will (which denies determinism).

Core claim

To be free in the morally relevant sense is to act according to one's own will, to do what one wants, in the absence of external constraint or coercion, even if what one wants is itself the product of prior causes. The standard slogan: "Free will is not the freedom to choose your desires; it is the freedom to act on them."

The crucial compatibilist move is to reject the principle that moral responsibility requires alternative possibilities (PAP). On the libertarian / classical view, an agent is responsible for an action only if she could have done otherwise. On the compatibilist view, responsibility requires only that the action flow from the agent in the right way, from her own desires, character, and reasons, even if she could not, in the strict metaphysical sense, have done otherwise.

Distinguish from rivals

vs. Hard Determinism, both affirm causal determinism; hard determinists conclude free will is illusory and moral responsibility ungrounded; compatibilists conclude free will is real but redefined.
vs. Libertarian Free Will, both affirm free will; libertarians deny determinism (require contra-causal freedom and PAP); compatibilists accept determinism and redefine freedom.
vs. hard incompatibilism (Pereboom), agrees that if incompatibilism is true, free will fails; disagrees with hard determinists by remaining open about the truth of determinism while still concluding against responsibility.

Two flagship arguments for compatibilism

Frankfurt cases (Harry Frankfurt, "Alternate Possibilities and Moral Responsibility," 1969). Frankfurt constructs cases in which an agent does X on his own, while a counterfactual intervener stands ready to make him do X if he were going to deviate. The agent could not have done otherwise (the intervener guarantees X), yet we still hold him responsible because he did X on his own. Conclusion: PAP is false; responsibility doesn't require alternative possibilities. This is the leading 20th-c. anti-PAP argument.
Hierarchical / mesh accounts (Frankfurt, Freedom of the Will and the Concept of a Person, 1971; Gary Watson; John Martin Fischer's guidance control). An agent acts freely when his action issues from desires he reflectively endorses (second-order volitions that mesh with first-order desires) and from a reasons-responsive mechanism. Freedom is structural, not metaphysically uncaused.

Theological compatibilism

The standard Reformed account, decisively shaped by Jonathan Edwards' Freedom of the Will (1754):

The will is the mind choosing. The will is not a separate faculty floating free of the intellect and affections; it is the agent inclining toward what he most desires. To "will" is to incline.
Freedom is doing what you want. A man is free when he acts according to his strongest motive and inclination, without external compulsion. He is not free when chained, hypnotized, or coerced.
The will is not self-determining. The choice always follows the strongest motive, which is in turn determined by the agent's nature and circumstances. To will against one's strongest motive is incoherent, it would be willing what one doesn't will most.
Application to soteriology. Fallen humanity is unable to choose God not because of external constraint but because of internal disinclination. The unregenerate freely (i.e., according to their actual desires) reject Christ; the regenerate freely (i.e., according to their newly given desires) embrace Christ. Regeneration changes what the will inclines toward.
Application to divine concurrence. God's effectual decree determines the regenerate's choice without coercing it; the regenerate genuinely wants what she chooses. Sovereign decree and free creaturely choice are non-competitive.

Biblical foundation (compatibilist reading)

God works the willing. Phil 2:12-13, "work out your own salvation... for it is God who is at work in you, both to will and to work for His good pleasure." Divine and human agency in the same act.
The plans of the heart and the answer of the tongue. Prov 16:1, Prov 16:9, humans plan; the Lord directs the steps.
God hardens and has mercy. Rom 9:18; Exod 9:12 (God hardens Pharaoh) alongside Exod 8:15 (Pharaoh hardens his own heart), the same act ascribed to both.
Joseph's brothers, Gen 50:20: "you intended evil against me, but God intended it for good." One event, two intentions, both real.
The crucifixion as paradigm, Acts 2:23; Acts 4:27-28, the cross was both God's "predetermined plan" and the genuinely free, culpable act of Herod, Pilate, and the people.

These texts, on a compatibilist reading, attribute the same act to both divine determination and creaturely volition without contradiction, which only the compatibilist framework can coherently sustain.

Historical development

Stoicism (early proto-compatibilism), Chrysippus distinguished fated events from what is up to us, anticipating a freedom-of-character account.
Augustine, the bound will of De Libero Arbitrio and the late anti-Pelagian writings: fallen humanity freely sins (because that's what it wants) but cannot do otherwise without grace. Functionally compatibilist.
Aquinas, on some readings; voluntary action proceeds from the agent's own intellect and will, even though the intellect is moved by the apprehended good.
Luther, De Servo Arbitrio / Bondage of the Will (1525), against Erasmus. The will is bound to its strongest inclination; "freedom" of the will to choose against its inclination is a fiction.
Calvin, Institutes II.2-5: the will is fallen and its choices follow its (fallen) nature.
Jonathan Edwards, Freedom of the Will (1754), the canonical analytical defense. Distinguishes natural ability (the constitutional capacity to do X if one willed it) from moral ability (the inclination to will X). The fallen sinner has natural ability to come to Christ (no chains, no missing limbs) but lacks moral ability (no inclination); responsibility requires only the former.
20th-21st c. analytic compatibilism. P. F. Strawson, "Freedom and Resentment" (1962); Harry Frankfurt (1969, 1971); Daniel Dennett, Elbow Room (1984), Freedom Evolves (2003); John Martin Fischer's semicompatibilism; Susan Wolf.
Contemporary Reformed theology. D. A. Carson, Divine Sovereignty and Human Responsibility (1981); Paul Helm, The Providence of God; John Feinberg.

Spread of positions (where Compatibilism stands)

The standard secular position in mainstream contemporary philosophy of mind (Dennett, Frankfurt, Fischer).
The standard Reformed / Calvinist account of human freedom under divine decree.
Required by Calvinism (which holds determinism by divine decree and free human responsibility together).
Rejected by Arminianism, Molinism, and Open Theism, all of which require libertarian freedom as the only kind capable of grounding genuine moral responsibility.
Rejected by Hard Determinism (Sam Harris, Pereboom), which holds that compatibilism is a face-saving redefinition that cannot ground genuine responsibility once the determinist consequences are taken seriously.

Standard objections (steel-manned)

The "just changes the subject" objection. Compatibilism doesn't defend free will; it changes what "free will" means. If determinism is true and the agent could not have done otherwise, calling that "freedom" is a verbal evasion. (Pressed by Kant, William James, modern libertarians.)
The Consequence Argument (Peter van Inwagen, An Essay on Free Will, 1983). If determinism is true, our actions are consequences of laws of nature plus past states, neither of which we have any control over. So we have no control over our actions, and that is what genuine freedom requires.
The manipulation argument (Pereboom). If a neuroscientist could causally manipulate an agent's brain so that he forms exactly the desires that lead him to murder, the agent would still satisfy compatibilist criteria (acting on his own desires, no external coercion), but we wouldn't hold him responsible. So compatibilist criteria are insufficient.
The theological objection (libertarian). If the regenerate freely choose Christ but only because God determined them to want to, the "freedom" is verbal; the responsibility-grounding alternative-possibility is missing. Compatibilist reply: this reads PAP into responsibility precisely where Frankfurt cases show it doesn't belong.

Tensions

The Frankfurt-cases literature is voluminous and contested; libertarians have proposed responses (e.g., flickers of freedom, Kane's self-forming actions).
Theological compatibilism's relation to the Problem of Evil is sharp: if God determines all choices, He determines the choices that produce evil. Reformed compatibilists answer with distinctions between decretive and prescriptive will, between causing and permitting / ordaining, and with appeals to the greater-good theodicy.
The compatibilist account of moral responsibility under sin and grace is one of the most distinctive features of Reformed soteriology and one of the most contested.