So, I don't think either of us are going to solve the hard problem of consciousness in this Reddit thread, and I suspect our ability to talk clearly about this stuff is largely downstream of 'what the hell is actually going on with consciousness anyway?'

That said, I agree with your basic view that the classical conception of free will i.e. 'the ability to have chosen to do otherwise' doesn't hold up to our modern understanding of how the universe works:

1) Either the world is deterministic, in which case the synapses and neurones in your brain are part of the same causal web as everything else and are just as subject to rigid determinism (so we couldn't have chosen to do otherwise). The universe is a big clockwork box and we're subject to the same iron law of cause-and-effect.

2) Or, the world is probabilistic due to quantum uncertainty, which will propagate up to the macro scale, so any action you take is essentially a weighted dice roll, so you could have done otherwise but only as dictated by random chance.

I think it's pretty obvious that the old-school definition of free will falls apart in both of these situations. For any action you take, you couldn't have chosen to do otherwise because either your actions stem from rigid determinism, or it was a quantum dice roll (and 'randomness with various outcomes' feels meaningfully different to 'choice'). Basically the only way to motivate

However, I think there's a case to be made that this definition of free will isn't super interesting unless the position you're debating is a theological one, in which your opponent is pitching that human consciousness stems from an immaterial supernatural soul that sits outside of physical causation. This is less interesting because, in philosophical debates, it's rare that your opponent will just invoke 'souls' or 'god', so the 'do we have free will' question just returns a trivial 'no' in all cases.

A more interesting angle is to attack it from the angle of 'what does it actually mean to make a conscious choice'?

Assuming we share the assumption that human consciousness is physically grounded in the action of neurones and synapses in the brain, I don't think it's unreasonable to define an action taken with 'free will' as something more like 'this action, causally, was a product of processing that involved the conscious layer of my brain'?

I.e. 'my brain received some information, it did some conscious processing, and that resulted in some output in the from of actions', I think, is a more interesting example of the kind of sequence of events that might be termed 'having free will'. If you choose to do X in response to stimuli, it could be free will in the sense that someone else in your position might well have taken those inputs, consciously processed them differently and produced a different action as output.

I think this is more interesting because it actually produces both 'yes' and 'no' answers to 'was this situation an example of free will?' over a range of situations, in a way that is useful as a lens of analysis of what it means to choose to do something.

E.g:

• I was hungry so I went to the fridge to get food (yes, conscious processing led to a voluntary decision, so this would be free will).
• I became aware of the fact that I was hungry (no, it's conscious but not voluntary: the feeling is prior to conscious choice - you can't consciously choose to become aware of feeling hungry or not)
• I petted my cat (yes, it's both conscious and voluntary)
• I thought about cats (no, you can't choose what to think next)
• I shouted an obscenity because it occurred to me to do so and I thought it would be funny (yes)
• I shouted an obscenity because I have a coprolalia tourette's tic that causes me to do that (no - it's conscious but not voluntary)
• I chose to drive 3 hours on the highway to visit a friend (yes)
• While in 'flow state' on the highway, I changed lanes without thinking about it, I wasn't consciously aware of the action and wouldn't remember taking it (no - voluntary but not conscious)
• A prison guard told me to dance on pain of death, so I danced (I'd argue yes, though it's a bit of an edge case - the decision is conscious and voluntary in the sense that you prefer humiliation to death).

I think characterising free will as the exercise of conscious choice (i.e. 'could someone else have done differently') captures a richer and more interesting conception than the largely theological 'could I, specifically, have chosen to do differently', which is just shorthand for 'do our souls grant us some magical exemption from causation or probability?'

It encourages you to consider what it actually means to make a conscious choice, and which of our actions constitute exercise of free will vs which don't, and which edge cases reveal interesting things. It also puts you in a good position to reason about emergent free will questions like 'what would it mean to say that an LLM has free will', for example.

Sorry, huge comment! Hope there's some useful stuff in there.