[cbennett]

> Penrose appeals to quantum woo to claim that the human mind isn't strictly algorithmic.

Penrose doesn't appeal to quantum woo, he has a quite well articulated set of assumptions and arguments , related to loop quantum gravity [1], about how objective collapse of the wave function may occur at bio-physically feasible decoherence times.

Now, whether you think his biophysical theories of consciousness are valid, or even required (whether you buy the microtubules argument/hypothesis), is one thing. But stating that Penrose- arguably the 20th century's foremost mathematical physicist- is a practicioner and/or a spreader of 'quantum woo'-- that belies a level of mis-informantion so catastrophically high that it renders your quoted statement indistinguishable from a pure ad-hominem.

[1] https://www.wikiwand.com/en/Loop_quantum_gravity

[cbennett]

@Chronos (can't reply for some reason, so I'm just replying to my own post and tagging you)

Its true that LQG is not known a natural schema to implement hyper-computation. However, since we don't well understand the time-dynamics of twistors ( how these operators may interact non-linearly through time), i don't see any a-priori reason why it is not a possible scheme for super-computation (you could make a good counter- response based on occam's razor, which I'd grant).

Look, lots of thereotical CS folks get disturbed by the idea of hyper-computation/super-turing machines, but in truth Turing machines are a toy model in comparison to true physics; as such, it doesn't take a whole lot more to get something more powerful; Siegelmann and colleagues have shown that real weighted, analog recurrent nets have super-turing abilities [1] [2]. While Aaronson and other raise good questions about physical realizability of such systems, a good thing to keep in mind is that these discussions often take place at computational 'limit' cases, eg solving intractable PSPACE problems, which may not be as relevant to more pedestrian problems solvable by biological systems. Central point: dynamically evolving systems iteratively exploring through (from) in-consistent systems towards more and more consistent ones have many of the same compelling qualities we would call 'super-turing'. Also see the lit on evolving turning machines.

Finally, while I don't agree with the magnitude your Pauling analogy, I certainly agree with you statement that Penrose is out of his depth here. While I do not , presently, buy his argument that quantum effects are necessary to realize consciousness, I remain open to the idea until we know more about BOTH physics and computation.

[1] http://www.mitpressjournals.org/doi/abs/10.1162/NECO_a_00263 [2] http://www.kurzweilai.net/super-turing-machine-learns-and-ev...

[Chronos]

LQG is not believed to allow hypercomputation, i.e. the solving of Turing-uncomputable problems. Penrose's entire argument is based on the idea that the human brain is a hypercomputer, which is why it cannot in principle be simulated by a computer (or any other machine).

It's worth noting that Penrose's field of expertise is General Relativity, not quantum physics, and definitely not Computer Science / philosophy of computation. I see the situation with Penrose as equivalent to Linus Pauling's unfortunate foray into Vitamin C pseudoscience late in his life.

[manyoso]

Penrose' claim is much simpler. He thinks that gravity playing a role in wave function collapse will show that non-quantum computers are incapable of accurately modeling quantum gravity. IOW, he thinks gravity will end up showing the physical Church-Turing thesis to be false.

Say what you will about Penrose, but can you seriously deny that he is one of the world's foremost experts on gravity?? You might not like his conclusion, but to say that he is out of his element here is ridiculous. Are you in your element when discussing gravity causing wave function collapse? Who do you think would be more in their element on this subject than Penrose??

[Chronos]

Call me back when Penrose convinces a well-regarded quantum physics expert. At that point we can call up Scott Aaronson and ask him his opinion, as Aaronson is an expert on the intersection of quantum physics and computing.

[manyoso]

Scott is a friend of mine. I've talked with him face to face about this very subject. He disagrees with Penrose, but his objections are far more nuanced and respectful than anything I have seen here. He would be horrified to see Penrose belittled and his arguments not given a fair reading. Penrose is an intellectual hero to Scott and someone to be admired.

[cbennett]

That's good to know. I read his post on his 'debate' with Roger and really enjoyed it. Also of interest may be the discussion between him and Hameroff in the comments section. Meta-comment: It a sad sort of situation when intellectual communities, whether they be HN or another, tend to idolize a set of individuals and demonize others. Thanks @manyosos for your comments in this thread, you really helped elevate the discourse.