[The_Colonel]

> In principle, that observer is able to calculate the system's evolution exactly

Which is fine, actually even more, it's confirming the presence of free will.

I have a Snickers bar in front of me. I like Snickers, but I also want my teeth healthy, keep diabetes away from me and keep my weight in check. I will decide to either eat it or not, depending on the current subjective trade-offs between my priorities. Acting on my wishes and priorities like this seems exactly in line with free will.

In your understanding, what behavior does an observer need to see to detect free will for you? The decision cannot depend on my goals of feeling good eating Snickers / keeping my weight in check? Based on what should free will make decisions? If it's on nothing, should the behavior with free will be random? That seems very counter-intuitive.

> if it is bound by the laws of physics

As mentioned earlier, this is no external constraint in my physicalist understanding of the world - laws of physics are an inseparable part of "me" as a system.

[n4r9]

> The decision cannot depend on my goals of feeling good eating Snickers / keeping my weight in check?

You have conceded that your decision is pre-determined. Most people consider pre-determined events not to be "free". What are they even "free" from?

[The_Colonel]

> You have conceded that your decision is pre-determined

Yeah, "pre-determined" by "me" (physicalist definition above).

Isn't the ability to determine your decisions exactly free will?

[n4r9]

In my understanding of how the phrase is used, "free will" implies being free from pre-determination.

[The_Colonel]

That's completely opposite to my understanding - free will means to be able to determine your own decisions.

[n4r9]

I think I kind of get where you're coming from. Would you perhaps agree that the "free from" in your free will is "free from external influence"?

If so, consider the following thought experiment. Let's say I get to pick either an apple or an orange to eat. I'm confined to a white room and the state of the "me" system is such that I am pre-determined to pick the apple. Alice is standing outside the room in front of a button, which blasts an EM wave at my brain after which I am pre-determined to pick the orange.

So, my choice is determined by whether or not Alice presses the button.

Do I have free will when I make this choice?

What if, instead of Alice pressing the button, the wave is blasted with 50% probability?

[The_Colonel]

> I think I kind of get where you're coming from. Would you perhaps agree that the "free from" in your free will is "free from external influence"?

I agree only to a degree. I don't consider free will to be a binary thing, in some cases you exert more free will, in other cases you are more strongly coerced to do something. Like when I talk to my wife during breakfast, she (external entity) is exerting influence on me, but I don't think it cancels my free will.

I don't fully understand the mechanics of your experiment, but assume that this EM wave just completely overwhelms the signalling in my brain - in that case, it doesn't seem like I have (a lot of) free will. But you can design less extreme thought experiments, e.g. where Alice causes discomfort to me which then influences me to favor one of the options more strongly than otherwise, where I still keep some decision making / free will.

I'd say that how much free will you exert is determined by how much your decisions are driven by your internal "me" state vs. the external influence.