Free will and determinism

What it is

Determinism is the claim that every event, including every decision you make, follows necessarily from prior states of the world plus the laws that govern it. Free will is the capacity to be the genuine author of your own actions.

The question is whether both can be true. Three positions divide the ground:

• Hard determinism — determinism is true, so free will is an illusion
• Libertarianism (nothing to do with the politics) — we have genuine free will, so determinism must be false somewhere
• Compatibilism — the two are not actually in conflict, because free will was never about escaping causation in the first place

Compatibilism is the position most people find slippery on first hearing and most philosophers hold. Its claim is that freedom means acting from your own desires and reasoning, without external compulsion — not being uncaused. A person choosing tea over coffee is free; a person choosing under threat is not. Whether the first person's neurons were following physics is, on this view, beside the point. Freedom is about the kind of cause, not the absence of one.

Where it came from

The Stoics faced the problem directly, since they held both that fate governs everything and that virtue is up to us. Chrysippus reached for something close to compatibilism with his rolling-cylinder analogy: push it and it moves, but it rolls because of the shape it has. The push is external, the rolling is its own nature.

In Christian thought the problem became acute through divine foreknowledge and grace — Augustine wrestled with it, and it reached full heat in the exchange between Erasmus, who defended free will in 1524, and Luther, whose On the Bondage of the Will (1525) denied it in the strongest terms.

Hume gave compatibilism its modern shape. In the twentieth century, Harry Frankfurt's 1969 paper undercut a long-standing assumption: the idea that being responsible requires that you could have done otherwise. Frankfurt constructed cases where an agent could not have done otherwise — a device would have intervened had they wavered — but acted entirely on their own reasons, and where we still hold them responsible. The device never activated. If the intuition holds, alternate possibilities are not what responsibility rests on.

How it is used

A great deal of the territory this site covers quietly assumes substantial free will. Karma requires that actions be genuinely yours. Spiritual practice assumes you can undertake it. Every teaching that says you must choose, surrender, awaken or repent presupposes someone capable of doing so. The manifestation literature goes furthest, assuming an agency strong enough to reshape circumstance.

The traffic runs the other way too: determinism gets used to dissolve responsibility, and occasionally to dissolve the self along with it.

What we can and cannot say

We can say the philosophical consensus is not where popular writing assumes. Surveys of professional philosophers put compatibilism at roughly six in ten, with hard determinism a small minority. The common framing — science has shown free will is an illusion, and philosophers are catching up — misdescribes the field.

We can say the Libet experiments are the most over-interpreted result in this area. In 1983 Benjamin Libet found that a "readiness potential" appeared in the brain several hundred milliseconds before subjects reported deciding to flex a finger, and this is endlessly cited as the experimental refutation of free will. Three problems have accumulated. The task was an arbitrary, unmotivated movement — deliberately stripped of reasons, which is exactly what meaningful choice consists of. The timing of a conscious intention is measured by asking subjects to note a position on a fast clock, which is itself unreliable. And most damagingly, Schurger and colleagues argued in 2012 that the readiness potential may be an artefact of how the data are aligned: if spontaneous neural noise drifts, and you average trials backwards from the moment of action, you will generate a rising signal whether or not anything is building toward a decision. The experiment remains interesting. It does not show what it is usually said to show.

We cannot say the question is settled. Physics does not obviously help — quantum indeterminacy, if it scales up at all, buys randomness, and a decision that happens randomly is no more yours than one that happens inevitably. Nobody has produced an account of libertarian free will that is both intelligible and compatible with what we know about the brain, and nobody has produced a hard-determinist account that most people can actually live by.

Further reading

• Harry Frankfurt, "Alternate Possibilities and Moral Responsibility" (1969) — four pages, and it changed the shape of the debate.
• Daniel Dennett, Elbow Room (1984) — the most readable defence of compatibilism.
• Aaron Schurger et al., "An accumulator model for spontaneous neural activity prior to self-initiated movement" (2012) — the reinterpretation of Libet that popular accounts skip.