Free will · Quiz question 6/35
Laplace's Demon
If an intellect knew every particle and every law, it could calculate your whole future. Is it still fair to blame anyone in that world? Laplace's demon, explained.
Imagine a being that knows the universe's starting state and every law of physics — so it could calculate everything you'll ever do.
In that case, it isn't fair to blame anyone for a crime.
French mathematician Pierre-Simon Laplace introduced it in the preface to his 1814 Philosophical Essay on Probabilities: an intellect that knew all the forces of nature and the positions of everything at one moment would see "the future, just like the past" laid out before it. Later writers dubbed it "Laplace's demon." This question's second line — blame isn't fair — leads into the modern debate over whether determinism is compatible with moral responsibility.
Laplace's demon is the most vivid picture of causal determinism. If determinism is true, everything you'll ever do was already fixed by the state of the universe near the Big Bang plus the laws of nature. Peter van Inwagen turned this into the "Consequence Argument": the past and the laws aren't up to us, our actions follow from them, so our actions aren't up to us either.
Nichols and Knobe (2007) found that when a deterministic universe is described abstractly, most people say nobody can be held responsible — but add a concrete criminal and most say he is responsible. So how this question felt to you may depend on framing.
Quantum mechanics later suggested the micro-world may not be deterministic. But many philosophers point out that adding randomness doesn't create responsibility either.
If determinism is true, blame and punishment are ultimately unjustified. Punishment can only be defended for prevention or rehabilitation.
Key names: Galen Strawson, van Inwagen (Consequence Argument), Gregg CarusoWhether blame is fair depends not on whether your action was determined, but on whether you could respond to reasons.
Key names: Daniel Dennett, Harry Frankfurt, P. F. StrawsonIf the real world isn't deterministic, the worry doesn't get off the ground — though whether chance gives us freedom is another question.
Key names: Robert Kane