Compatibilism holds that free will and determinism can coexist, whereas incompatibilism holds that they cannot. Incompatibilists must therefore reject either free will or determinism.
The Core Distinction
Determinism is the view that every event, including each human decision, is necessitated by prior causes and the laws of nature. The disagreement concerns whether a causally determined action can still count as free.
Compatibilists redefine freedom so that it does not require an action to be uncaused. A person acts freely when the action follows from their own desires, beliefs, and intentions without external coercion or constraint. For example, choosing to study because you want to improve your grade may be free even if your motivation has prior causes.
Incompatibilists argue that genuine freedom requires more than acting according to internal desires. If prior causes made the decision inevitable, the agent could not genuinely have acted otherwise and may lack moral responsibility.
| Position | Relationship between free will and determinism | Main implication |
|---|---|---|
| Compatibilism | They can coexist | A determined action may be free if it expresses the agent's desires without coercion. |
| Hard determinism | They are incompatible, and determinism is true | Free will does not exist. |
| Libertarianism | They are incompatible, and free will exists | At least some human actions are not determined. |
Both hard determinism and libertarianism are therefore forms of incompatibilism, although they reach opposite conclusions. Soft determinism is commonly used for the compatibilist view that determinism is true but humans can still act freely.
A common misconception is that incompatibilism means denying free will. This is incorrect: hard determinists deny free will, while libertarians defend it by rejecting determinism.
IB Exam Technique
In an IB Philosophy response on freedom, define determinism and free will before comparing the positions. Do not merely label philosophers: explain the criterion of freedom each position uses, apply it to an example, and evaluate whether freedom requires the genuine ability to do otherwise or only action without coercion.