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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 s

by davmre 10y ago

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".

davmre 10y ago
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 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!)
- foldr 10y ago
  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.
foldr 10y ago
>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.)
- davmre 10y ago
  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.

by davmre 10y ago

davmre 10y ago

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 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!)

foldr 10y ago
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.

foldr 10y ago

>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.)

davmre 10y ago
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.