---
title: Free Will and Determinism
section-id: metaphysics
sort: 130
author: Prof. James Okafor
created: 2026-02-10 09:00
modified: 2026-03-18 10:00
language: en
description: The debate between compatibilism and incompatibilism, and the significance of free will for responsibility.
---

# Free Will and Determinism

Determinism is the thesis that every event, including every human action, is the inevitable consequence of prior causes operating according to the laws of nature. If determinism is true, then given the state of the universe one billion years ago and the laws of physics, every action you have ever performed was already fixed. The question of free will is whether this is compatible with moral responsibility, and whether we have free will at all.

## The Basic Argument

The **consequence argument** (Peter van Inwagen) is the most influential argument for the incompatibility of free will and determinism:

1. If determinism is true, our actions are consequences of the laws of nature and events in the remote past
2. We have no control over the laws of nature or events in the remote past
3. Therefore, we have no control over the consequences of these things, including our own actions

If sound, this argument shows that determinism rules out the kind of control necessary for free will and moral responsibility.

## Compatibilism

Compatibilists hold that free will and determinism are compatible. They argue that the free will relevant to responsibility does not require the ability to have done otherwise in an absolute sense; it requires only that the action flows from the agent’s own desires, values, and reasoning without external compulsion or internal pathology.

### Classical Compatibilism
Hume and Mill held that free will is simply **freedom from external constraint**: you act freely if nothing external compels you, if you could have done otherwise had you chosen to. On this view, the determinist challenge misidentifies what freedom requires. Freedom is not freedom from causation; it is freedom from a particular kind of causation (coercion, compulsion).

### Frankfurt Cases
Harry Frankfurt argued that moral responsibility does not require the ability to do otherwise. Suppose a neuroscientist has implanted a device in your brain that will make you vote for a particular candidate if you are about to vote differently—but the device is never activated because you vote for that candidate anyway. You could not have done otherwise (the device would have intervened), but you seem fully responsible for your action.

Frankfurt cases suggest that what matters is not alternative possibilities but the actual causal history of the action. Responsibility requires that the action flows from your own decision-making, not that you could have decided otherwise.

### Hierarchical Compatibilism
Frankfurt also introduced the distinction between **first-order desires** (desires to act in certain ways) and **second-order desires** (desires about what desires to have). A free agent is one whose will is in accordance with their second-order desires: they want to have the desires that motivate them. An addict who wishes they did not want to take drugs has a first-order desire that conflicts with their second-order desire—their will is unfree.

### Reasons-Responsive Compatibilism
John Martin Fischer holds that free will requires reasons-responsiveness: the mechanism producing the action is sensitive to reasons. A moderately reasons-responsive agent acts freely—not because they could have done otherwise in the actual world, but because they would have done otherwise in nearby possible worlds where the reasons were different.

## Incompatibilism

Incompatibilists hold that free will and determinism cannot both be true. They divide into:

- **Hard determinists**: determinism is true, free will is an illusion, and no one is truly morally responsible
- **Hard incompatibilists**: whether or not determinism is true, we lack the metaphysical kind of free will required for responsibility
- **Libertarians** (in the metaphysical sense): free will exists, so determinism must be false or inapplicable at the relevant level

### Agent Causation
Some libertarians posit **agent causation**: agents, as substances, initiate causal chains that are not fully determined by prior events. This preserves the intuition that the agent is the ultimate source of the action rather than a conduit for prior causes. Critics find agent causation obscure: how does a substance (rather than an event) cause anything? And if agent causation is itself undetermined, does this make action random rather than free?

### Indeterminism and Luck
Quantum mechanics suggests the world is genuinely indeterministic at the micro level. Does this help the libertarian? Not obviously. If your decisions are influenced by random quantum events, they seem less attributable to you, not more. The challenge for the libertarian is to find a kind of undetermined action that is genuinely attributable to the agent without collapsing into randomness.

## The Significance of the Debate

The free will debate matters because it bears directly on practices of praise, blame, punishment, and reward. If hard determinism or hard incompatibilism is correct, our practices of holding people responsible rest on a mistake.

P.F. Strawson argued in ‘Freedom and Resentment’ that the practices of holding responsible are not answerable to metaphysical theses in the way the incompatibilist assumes. The reactive attitudes—resentment, gratitude, indignation, love—are constitutive of interpersonal relationships and are not the kind of thing that could be abandoned in response to a philosophical argument about determinism.

## Summary

- The consequence argument holds that determinism is incompatible with free will
- Compatibilists argue that the relevant freedom is freedom from compulsion, not from causation
- Frankfurt cases challenge the requirement of alternative possibilities
- Hierarchical and reasons-responsive compatibilism refine the conditions for free action
- Libertarians posit agent causation or appeal to indeterminism; both face the luck objection
- Strawson’s reactive attitudes suggest the debate has less practical import than it seems
