[onceiwasthere]

This is what I always try to ask people. Is there even a possible definition of free will within the laws of physics? It seems to me to be blurry philosophy and nobody has the same definition. Not that it's invalid to talk about if there's no physical framework. But there's no scientific way we can talk about it that I've seen.

[AnimalMuppet]

If you accept that cause and effect holds in a closed system, then no, there is no possibility of free will. But within that viewpoint, everything we think of as making us human is dead. It's not just free will. Truth is dead. (You can't determine whether something is true, because you have no choice whether you believe it or not. All you can say is that you found the explanation convincing.) Morals are dead. (Both because you can't blame anyone for what they do, and because you have no ability to choose what you think is right or wrong.) Even love is dead, at least in the higher sense of choosing to do what's best for the other person, because you can't choose anything. And even in the lower sense of attraction, that's determined too.

The problem is, this view really doesn't match with our experience of what it means to live as human beings. We experience deciding. We become convinced that things are actually true. We love and are loved. We know, from direct experience of living as human beings, that this is not who we are.

This leaves a dilemma. Either our experience is wrong, or our initial starting point is wrong. Either the laws of physics are not what is "furthest back" (in Francis Schaeffer's term), or else we really are determined and our lived experience is an illusion.

[dTal]

Option 3 - your logical leap was invalid, and it is perfectly possible to be human and believe in truth and love and morality and all the rest of it, all within a deterministic physical system.

Choice is deterministic, but that doesn't make it less real - on the contrary, it gives your choices meaning! They have causes, reasons, justifications! It would hardly be preferable if your "choice" were the outcome of a fair dice roll, would it? What kind of choice would that be?

I think the problem arises from a confusion of of abstraction levels. At the level of atoms and chemical reactions, you are completely deterministic and "choice" isn't a meaningful concept. 10 stories up, at the level of thoughts and ideas, it is. This is no different than how "pressure" is a meaningful concept for a tank of air, but not a single air molecule.

[tanseydavid]

Is Brownian Motion deterministic or not?

If your view is that Brownian Motion is not deterministic then does that not contradict the idea 'that cause and effect holds in a closed system' as any sort of absolute?

[AnimalMuppet]

The subject was free will. I said "determined" in contrast to free will. So, if you've got Brownian Motion (or, worse, quantum uncertainty), then you've got some randomness in there, and it's not a purely deterministic system. But that doesn't give you any more free will; it just means that the machine that determines your choices has a random number generator as one of the inputs. You still don't get to choose, because you don't control the randomness.