Further reading matter.
Apr. 18th, 2004 02:51 pmYesterday there was a Guardian article about the philosopher (and sculptor, and jazz pianist, and sailor, and cidermaker . . .) Dan Dennett, who it turns out is a man too talented to be allowed to live. I have recommended his work to some of you before - especially Consciousness Explained and Darwin's dangerous Idea.
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Date: 2004-04-18 08:11 am (UTC)no subject
Date: 2004-04-18 11:19 am (UTC)I thought the best bit was the Turing reprint, where he summarises Penrose's position on consciousness in one sentence and then dismisses it in the next. Written in the early fifties, of course.
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Date: 2004-04-18 11:37 am (UTC)http://www.abelard.org/turpap/turpap.htm#contrary_views_to_the_main_question
I'm afraid that Penrose's view is much closer to my own than Dennett or Hofstadter (though I think the latter two are better writers). Penrose was widely (and unfairly I thought) criticised for providing arguments in principle not proofs. Fundamentally I have much sympathy with his main thrust, that nothing we currently know about in physics can genuinely explain consciousness.
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Date: 2004-04-18 11:56 am (UTC)no subject
Date: 2004-04-18 12:11 pm (UTC)Yes, or better phrased, that nothing in current physics can explain consciousness. To me this is self-evident. I would have willingly accepted that as an axiom.
therefore the only major hole in it - gravity - must therefore take a particular form
I wish my copy of emperor wasn't in my office (and my copy of shadows is missing presumed lent)... that is certainly not what I took away from it. Certainly he wished to argue for a certain form of those physical laws - he's something of an expert there. But again, I recall this differently - that that was an optional part of his argument about minds... "Having done all that, I wish to convince you of that the following is one possible way forward..." I would say that his argument did not in the slightest rely on any particular form of theories on gravitation.... he just wished to champion one.
The fact that this all follows from a reading of Gödel that pretty much everyone else thinks is hilariously wrong
That was part of what I meant about the condemnation. I wouldn't say his reading of it was hilariously wrong but I would agree it is wrong. But his position was not that everything followed from that... his position remained tenable without that part of the argument and that is how I took his position. I did not believe his argument via Goedel was correct but having removed it totally the rest of his position was still intellectually sufficiently coherent for me.
[What is interesting, is that while everyone agrees that his interpretation of Godel is wrong there's a considerable amount of disagreement about WHY it is wrong -- which is in itself intriguing. If the experts in a field are all totally in agreement that someone is wrong in mutually contradictory ways then that at least tells you things aren't as simple as they might appear.]
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Date: 2004-04-18 12:47 pm (UTC)No, that implies that consciousness is something to be explained in terms of physics. It's not the same thing at all.
that is certainly not what I took away from it. Certainly he wished to argue for a certain form of those physical laws - he's something of an expert there.
Well, he needs a physical interaction that is only described by a non-computable description. We don't have any such thing, and the only obvious place for such a thing is in gravity. I'm not aware of any practical reason to suspect that any physical process would be like that. It's consequent on his reading of Gödel - Dennett asked him personally which way round the argument was suppose to work. He's not trying to argue the gravity line from his knowledge of physics.
I did not believe his argument via Goedel was correct but having removed it totally the rest of his position was still intellectually sufficiently coherent for me.
I read a TLS review of Emperor before I read the book itself. There was a summary of his argument and I counted points in it that I as a biologist thought were definitely or probably wrong, or entirely speculative. 27, as I recall. Without his argument from principle, it collapses like a stack of cards.
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Date: 2004-04-18 12:12 pm (UTC)http://psyche.cs.monash.edu.au/v2/psyche-2-06-moravec.html
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Date: 2004-04-18 01:57 pm (UTC)no subject
Date: 2004-04-18 03:11 pm (UTC)1: Because of the arguments of Lucas and Searle, we know that consciousness cannot be implemented on a Turing machine.
2: But everything we know how to build using the laws of modern physics can be implemented on a Turing machine.
3: So there must be a super-Turing bit of physics hiding in Nature that we don't know about.
4: Where's a big unknown place to put it? How about Quantum Gravity?
5: How the hell can QGT act on the brain? Through, er, weird tubule thingys?
His presentation of Lucas's argument is superb and the most compelling I've ever known. I don't have a good knock-down reply; the best counter-argument is the seemingly insurmoutable problems you encounter when you try and bridge over what seem at first to be petty, trivial problems with it.
His falling for Searle's emotionally-laden nonsense, on the other hand, is just embarrassing in one so bright.
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Date: 2004-04-18 03:26 pm (UTC)I would say that actually Penrose believes this as his starting hypothesis but introduces the arguments of Lucas and Searle since they are classically used in such a situation. [You must admit that any decent coverage of the strong AI hypothesis would have to include those arguments.]
2 : But everything we know how to build using the laws of modern physics can be implemented on a Turing machine.
I do not believe this part is true and I do not believe Penrose claims it. If there is a 50% chance that an atomic particle decays in time x how do you simulate that with a TM? [Answer, you can't without a hidden variable.]
His falling for Searle's emotionally-laden nonsense, on the other hand, is just embarrassing in one so bright
I believe Searle reversed his position a few years back. [And, as usual with AI type debates, countered his own argument with a different (and mutually contradictory) argument to the critics.]
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Date: 2004-04-19 12:32 am (UTC)If there is a 50% chance that an atomic particle decays in time x how do you simulate that with a TM?
When discussing computability classes like BPP or ZP, one posits a Turing machine with access to a source of randomness. That's not the sort of uncomputability Penrose is thinking of. He concedes that physics as we know it does not give you the stuff to build a super-Turing machine; that's why he introduces the discussion on QGT.
His is by far the most intellectually careful and rigorous defence of biological supremacism ever, IMHO. Searle says (from memory) "In answer to the question 'can a machine think?' we answer 'yes, we are such machines". But he never takes seriously explaining what's so special about brain-stuff that computer-stuff can't do the same think. Penrose rises to the challenge.
I believe Searle reversed his position a few years back.
I heard Searle speak in public fairly recently and his position did not seem much different.
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From:Here's what my colleague recommended:
From:Re: Here's what my colleague recommended:
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Date: 2004-04-18 03:35 pm (UTC)Having said that I thought Searle had himself recanted I can now find no clear reference and am worried I have misremembered.
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Date: 2004-04-18 03:45 pm (UTC)taken from http://www.artsci.wustl.edu/~philos/MindDict/searle.html [I thought that to some extent Searle had himself recanted on the Chinese Room argument but I could not remember the details.]
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Date: 2004-04-18 03:47 pm (UTC)Incidentally, Feynman, in '82 proved that this could not be done with Quantum Electrodynamics without an exponential increase in the time taken for the computations.
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Date: 2004-04-19 12:35 am (UTC)(no subject)
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Date: 2004-04-19 03:40 am (UTC)Finally got into the office so I can check my copy. Searle's arguments are mentioned on only three pages according to the index. Penrose says of them "I think that Searle's argument has considerable force to it even if it is not altogether conclusive... it _suggests_ [his italics] (but no more) that no algorithm, no matter how complicated, can ever, of itself alone, embody genuine understanding..." [p26 in my paperback copy of ENM.]
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Date: 2004-04-18 08:23 am (UTC)no subject
Date: 2004-04-18 11:18 am (UTC)no subject
Date: 2004-04-18 11:19 am (UTC)no subject
Date: 2004-04-18 11:32 am (UTC)no subject
Date: 2004-04-18 11:59 am (UTC)No, we dont. Really we don't.
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Date: 2004-04-18 12:55 pm (UTC)Actually I haven't done that *yet*, but it's only a matter of time.
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Date: 2004-04-18 05:03 pm (UTC)http://arxiv.org/abs/quant-ph/0203034
I suspect it will be refuted soon but I bloody hope it is true because it will make the universe a more interesting place.
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Date: 2004-04-19 02:10 pm (UTC)Is there anything left that you and Paul haven't done to death yet, or can I get to sleep?