It feels like this is mostly a disagreement over language. We all agree that determinism and "predictability" are independent questions. You've equated "free will" with non-determinism and therefore see predictability to be orthogonal, whereas Aaronson equates "free will" with non-predictability, making determinism orthogonal though I imagine he'd argue for it on other grounds. It's not clear that there's an actual disagreement over anything except which words to use for which concepts.

FWIW, I think Scott has read more of the philosophical literature on free will than probably anyone else in the world with a comparable level of quantum-physical expertise. If he's too confused to be allowed to discuss these issues, then what is the path by which philosophers expect to stay relevant and up-to-date with new knowledge? A field whose currency of legitimacy is "you must have devoted your life to understanding every detail of dispute in the existing literature" is not a living field that hopes to learn from outsiders and grow with new scientific inquiry. I think the best philosophers recognize this, and are willing to engage more broadly.

I wouldn’t equate free will with physicalism. It’s possible that physicalism might entail the absence of free will (I don’t claim to know the answer to this question), but it’s pretty clear that the entailment doesn’t go in the other direction.

I’m a bit frustrated here, because physicists often seem to retreat to this position that it’s all just a question of terminology once people start pushing back against their philosophical claims. If Aaronson actually is using terms in such a weird way as you suggest, then I just have no idea what he is on about. We already have a perfectly fine word that means unpredictable; there’s no need to repurpose “free”.

I admit that I have no way of knowing what he has or hasn’t read, and my comment on that was snarky. But he doesn’t refer to any philosophical work in the interview, and I couldn’t find much published work by him that really engages with the current literature.

I think Aaronson believes the following. If there are provably no experiments that could differentiate a propery X from "free" then X is equivalent to "free." I think unpredictability passes that test.

Hmm, that seems like a fairly banal observation. Of course you can't tell whether someone has free will looking from the outside. In the general case the behavior of someone with free will will be indistinguishable from random behavior. If free will was just about patterns of behavior then it wouldn't be a very interesting philosophical issue.

Here's the paper he wrote on it, I think it'd be good to take a look at it directly.

https://arxiv.org/abs/1306.0159

Scott is making a pair of claims: If it's possible to build a fast, noninvasive, perfect predictor then what more can science say to show that people don't have free will?

If it's impossible to build such a predictor, for some fundamental reason, then what more can science say to show that free will exists.

Ah, in the paper he says that he's not actually talking about free will. That makes it less confusing. But I still think he's making much too strong a connection between Knightian unpredictability and free will. I don't see any reason at all to think that the former is a necessary condition for the latter, and he doesn't really attempt to argue the point. (He promises that he's going to argue it in section 2.5, but then section 2.5 ends up only talking about problems of personal identity.)

>Of course you can't tell whether someone has free will looking from the outside.

Before quantum mechanics and uncomputability, the "of course" went the other direction.

I don't see how that makes any difference. Could you expand?

I don't think it's obvious that you can't tell whether someone has free will from the outside. Considering the enormous success physics has had with explaining every other phenomenon from the outside, that seems like a very strong statement.

How would you distinguish decisions that were freely made from decisions made at random?

If we can't, then that says something doesn't it?

I just don't see how. It seems like a fairly obvious point that the two systems would be indistinguishable from the outside.

In that case, the pragmatists would say that the distinction isn't meaningful, that free will is a concept with no meaning, and end the debate there.

I don't think it's plausible to maintain that the question of whether or not we have free will is "meaningless". Any criterion of meaningfulness that derives that conclusion is probably faulty.