On 5/8/2015 6:38 PM, LizR wrote:
On 9 May 2015 at 11:24, meekerdb <[email protected] <mailto:[email protected]>> wrote:On 5/8/2015 2:58 PM, LizR wrote:On 9 May 2015 at 09:02, meekerdb <[email protected] <mailto:[email protected]>> wrote: On 5/8/2015 1:33 AM, LizR wrote:On 8 May 2015 at 18:37, meekerdb <[email protected] <mailto:[email protected]>> wrote: On 07 May 2015, at 14:45, Bruce Kellett wrote: We can use an original biological brain, or an equivalent digital replacement -- it does not make any significant difference to the argument. The first point is that in some conscious experience, be it a dream or anything else, there might be a portion of the 'brain' (in quotes because it can be biological or digital) that is not activated, so this can be removed without affecting the conscious experience. This idea of removing unused parts of brain so only "active" elements remain, seems problematic to me and not just because of counterfactual correctness. The ability to do this is implicit in the assumption that the physics of the brain is classical. But comp is based on the assumption that consciousness is the result of classical computation. If that assumption's wrong then comp fails, of course, from step 0 - no need to worry about the MGA.Bruno points out that a classical computer can compute anything that a quantum computer can so it doesn't exactly fail; what I think it implies that the classical computation must include the "environemnt", i.e. all the extra physical degrees of freedom and entanglement that make the brain computation (approximately) classical. That sounds like putting the cart before the horse. The question is, can the brain and environment be extracted from the assumption that consciousness is classical computation? Which is, of course, still an open question.True, it's a problem from either end. If you just assume computation is fundamental then you have to get QM out of it and ALSO the approximate classicality of the physically realized computation. Exactly. That is Bruno's problem.Plus, assuming no quantum entanglement with the environment is involved in consciousness (as seems likely given the decoherence times of neurons etc)That's not taking the QM seriously. QM says that it's the decoherence due to entanglement with the environment that produces the classical behavior.OK, I think even with a little brain I'm beginning to see the point here. I'm not yet sure if it's relevant, however. I think Max Tegmark's point was that the environment of a neuron is other neurons (and the surrounding material - glia, blood, etc) and that everything in a brain is decohering far faster than than the timescales of consciousness. Why would taking the QM seriously prevent the brain behaving as a classical computer on those timescales? Or to move the question into a (perhaps) better known realm, why would it stop a computer running an AI programme behaving as a classical computer?
It wouldn't, up to a very good approximation.
If the brain is fundamentally different to an AI due to quantum effects, that invalidates comp at step 0 (and possibly invalidates strong AI as well).
Well that's where I'm concerned about the difference between saying yes to a doctor who will replace a part of my brain with a physical, quantum mechanical device that is approximately classical (like my neuron was) and saying yes to a doctor who will replace part of my brain with an abstract Turing machine device that acts perfectly classical. I could say yes to the first and no to the second without invoking any magic or superstition (as Bruno accuses me of). I might reflect that the way my neuron came to behave classically was by quantum entanglement with the environment and that might be essential to my consciousness. It wouldn't prevent strong AI, it wouldn't prevent Bruno's argument from going through, it would just require that the scope of the counterfactuals in the MGA encompass essentially everything, because my brain is entangled with practically everything that was ever on my past light cone.
Or maybe it can be shown that all that entanglement averages out and makes no difference, i.e. there's not significant difference between mostly classical and exactly classical.
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