Determinism (as relevant to free will): All events in our bodies are determined by previous events (inside and outside of our bodies), in a chain that goes back to before our conception. If one knew the state of the universe then, one could predict it now.

Indeterminism: Determinism is false.

Compatibilism: It is possible for both determinism to hold and free will to exist at the same time.

Incompatibilism: If determinism is true, there is no free will.

Hard determinism: Incompatibilism and determinism are both true and so there is no free will.

Soft determinism: Compatibilism and determinism are both true and there is free will.

Libertarianism: Compatibilism and determinism are both false and there is free will.

	Determinism	Free will	If there were determinism, could there be free will?
Determinist	YES	(need not have a position)	(need not have a position)
Indeterminist	NO	(need not have a position)	(need not have a position)
Compatibilist	(need not have a position)	(need not have a position)	YES
Incompatibilist	(need not have a position)	(need not have a position)	NO
Hard determinism	YES	NO	NO
Soft determinism	YES	YES	YES
Libertarian	NO	YES	NO

· Why would someone accept determinism?

o “Our bodies are physical objects. Physical objects always behave the same way when placed in the same circumstances. For instance, if you drop a rock in a vacuum on earth, it always accelerates at 9.8 m/s². If you have two massive objects and the only force is gravity, then the first object will accelerate towards the other with acceleration –Gm₂/r². Chemical processes, likewise, act the same way. You can look up the reaction rates at a given temperature, etc. If you knew what angle and velocity a coin was tossed at…”

o This does not mean that in practice we can do the prediction. Chaos.

· Problem for free will.

o If determinism is true, then how you are going to act is already determined by how the universe was arranged before your conception. (It was determined which sperm and egg would meet, what kinds of environmental influences there would be, etc.)

o But if it was determined by how the universe was arranged before your conception, then you could not have done otherwise than you had done. You couldn’t have helped yourself. And just as we don’t hold responsible someone whose hand was forced, so, too, neither should we hold responsible someone who was predetermined to act a certain way.

o Those who accept this argument are incompatibilists.

o There are two kinds of them. Hard determinists and libertarians.

o But Hume rejected the argument. He was a compatibilist. In fact, he thought that at least some determinism was necessary for freedom and responsibility.

§ Why?

§ According to Hume an action is free provided it is done because one wants to and it wouldn’t have been done if one didn’t want to.

· However, most physicists think determinism is false for quantum phenomena.

o They could be wrong.

o Also, macroscopic phenomena still appear to be deterministic, at least approximately. (E.g., 99.99999% probability, etc.) It’s true that this is only approximate, but it does seem unlikely that freedom would hinge on that small difference. Maybe brain processes are like that.

o Moreover, quantum phenomena are random. It is not clear how random phenomena could contribute to freedom. Fred is no more free if his brain is run by clockwork than if it is run by random coin-flipping. The reason determinism seems to threaten free will is that it traces the actions ultimately to things the person is not responsible for. But a person is also not responsible for random quantum phenomena in her brain. In fact, that an action happened due to random quantum phenomena would seem to make one less responsible for it than if it had been determined by one’s character. Ergo, it seems someone who believes in free will should not think that our actions come from quantum phenomena. (Robert Kane disagrees.)