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I think you're missing the point somewhat. Yes, Aaronson assumes that something like physicalism is true, which I think is fairly defensible as a 21st-century scientist. But the argument isn't as simple as "physicalism entails the absence of free will". His point is that even if our actions are (probabilistically) determined by a set of underlying physical laws, it may still be that the character of those laws is such that it is fundamentally impossible to predict future actions, in which case we would still have meaningful free will.

The main form of prediction-impossibility he mentions is that our minds might depend meaningfully on quantum states, which are governed by the no-cloning theorem and therefore impossible even in principle to extract. Whether or not this is true is an open question, but the characterization of free will in terms of the concrete question "is it possible to build a prediction machine?" seems like a useful and novel contribution that doesn't just reduce to the old question of "is physicalism true".

To follow up: I personally see some extra subtlety here, in that even if a prediction machine did exist, we could still have a meaningful form of free will, because that machine would be governed by Rice's theorem (https://en.wikipedia.org/wiki/Rice's_theorem), which says that in general the only way to predict the outcome of a computation is to run the computation. (this is closely related to the halting problem).

That is, even if I could capture the relevant aspects of your mind state on a computer, i.e., the no-cloning theorem is not a barrier, it's still the case that the only way for me to predict what you will do in two minutes' time is to actually run your mind inside the computer for two minutes of subjective time. This would constitute a prediction machine in Aaronson's sense, assuming the computer could run faster than realtime. But since the computation that occurs is literally following your thought process step by step (Rice's theorem says there are no shortcuts), there's a real sense in which the decision was not determined until you -- the version inside the computer -- actually made it.

Of course this account depends on a functionalist/computational theory of mind, which can be quibbled with in all sorts of ways. But it does seem important for the philosophical discussion on free will to at least take into account the things we now know about the nature of computation, the character of physical law, and other scientific/mathematical questions, that were not known decades or centuries ago when the philosophical battle lines were being drawn. Yes, scientists can be arrogant and are often just wrong or deeply misinformed on philosophical questions. But that doesn't remove the responsibility of philosophers to engage with the frontiers of knowledge on these issues, which means engaging with people like Scott rather than just dismissing them as "confused". (as if anyone thinking about free will has ever not been confused!)

I don't exactly disagree with you (although let me point out that I said the discussion was confused, not Scott), but I'm not sure where people get the impression that philosophers aren't engaging with physicists on these questions. The ramifications of quantum physics for free will have been discussed endlessly by philosophers, and often by philosophers who have a significant amount of training in physics.

>But the argument isn't as simple as "physicalism entails the absence of free will".

Right, I said that's probably all he should say.

>His point is that even if our actions are (probabilistically) determined by a set of underlying physical laws, it may still be that the character of those laws is such that it is fundamentally impossible to predict future actions, in which case we would still have meaningful free will.

It's hard to see how it makes any difference to my level of freedom whether someone else can successfully predict what I'm going to do. You can predict pretty reliably that I'm going to have breakfast in the morning, but it's still a free decision on my part.

>but the characterization of free will in terms of the concrete question "is it possible to build a prediction machine?" seems like a useful and novel contribution that doesn't just reduce to the old question of "is physicalism true".

It seems to me that the question of whether or not we have free well is largely orthogonal to the question of whether or not our actions are predictable. I suspect that all four combinations of predictable/unpredictable and free/unfree are logical possibilities. So I think Aaronson is conflating a lot of things that ought not to be conflated, and which have been endlessly and subtly picked apart in a philosophical literature that he appears not to have bothered reading. (I haven't read that much of it either, but it already contains pretty much every idea about free will that is likely to occur to anyone in our present state of knowledge.)

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.

http://plato.stanford.edu/entries/pragmatism/

The caveat “external to [us]” is doing a lot of work here

I think it's just sloppy discussion.

Any hard-determinist will say that every interaction is pre-determined based on a previous interaction. The compatibilist approach tries to reconcile hard-determinism with the illusion of free will in a reference frame of the individual - but I think falls apart. I think Aaronson is trying to convey this particular philosophy.

"if you knew the complete state of the universe, you could use it to calculate [either deterministically or probabilistically] everything I’d do in the future."

Fortunately for us, Godel explored this exhaustively and concluded (though did not prove) that this is not possible. See also the Munchhausen Trilemma of proofs for problems proving any epistemological inquiry.

[1]https://en.wikipedia.org/wiki/Hard_determinism

[2]https://en.wikipedia.org/wiki/Compatibilism

[3]http://plato.stanford.edu/entries/goedel-incompleteness/

[4]https://en.wikipedia.org/wiki/M%C3%BCnchhausen_trilemma

> Godel explored this exhaustively and concluded (though did not prove) that this is not possible

While I agree that Aaronson's take on philosophy is not very original or profound, I don't think that Gödel concluded anything of the sort, and if he said something in that vein (assuming you're referring to the discussion on mechanism in the link you're provided), it is more an expression of his faith that any problem can be solved (and since not every problem can be solved by a machine, the mind is more powerful than any machine) -- hardly a conclusion.

Sharp response! Yes, the "external to us" caveat is very powerful because it is contextually ambiguous and its scope can potentially reach the location of every atom in the universe. Every atom in the universe is not trackable because they are not self-tracking. The only way out is retreat into, "we're in a simulation..."

Yes, very well put. I really enjoyed his technical answers, but when he dives into the philosophy I was disappointed to see the same very naive and narcissistic attitudes so many scientists have (that are even alluded to at the beginning of the article): you don't need to try to understand philosophy, just use your superior STEM brain and technical intuitions and if you think about it for a few minutes, with a healthy splash of "assuming my thesis, it is obvious my thesis is correct" , the problem is trivial -- why have people been thinking about it for centuries?

Agree completely. I don't think you deserve to be downvoted for saying that. Everything Aaronson's saying on this topic has been exhaustively discussed in the philosophical literature.

I don't think I deserve it either but I am not surprised or particularly offended. Pop scientists like Dawkins and NDT are rightly mocked when they say things like this because we can safely feel superior to them, but a tech golden boy like Aaronson can do the exact same thing and since he knows about quantum and does computer science it doesn't matter what he says or how far out of his depth he ventures any comment about him which doesn't border on hero-worship is verboten.

Downvotes or no it's worth saying. Defending any social science or humanity at all is hard work on a forum like this, but I think it's important.

He was asked about his opinion on free will and he gave it. I don't see where he is disdaining philosophy or saying his explanation is superior to anything.