bogus comments on The two insights of materialism - Less Wrong

18 Post author: Academian 24 March 2010 02:47PM

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Tags: physicalism monism metaphysics ontology dualism physics supernaturalism naturalism materialism

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Comment author: mattnewport 25 March 2010 05:42:31PM 0 points [-]

As far as I can tell from looking at those links both Searle and Pearce would deny the possibility of simulating a person with a conventional computer. I understand that position and while I think it is probably wrong it is not obviously wrong and it could turn out to be true. It seems that this is also Penrose's position.

From the Chinese Room Wikipedia entry for example:

Searle accuses strong AI of dualism, the idea that the mind and the body are made up of different "substances". He writes that "strong AI only makes sense given the dualistic assumption that, where the mind is concerned, the brain doesn't matter." He rejects any form of dualism, writing that "brains cause minds" and that "actual human mental phenomena [are] dependent on actual physical-chemical properties of actual human brains", a position called "biological naturalism" (as opposed to alternatives like behaviourism, functionalism, identity theory and dualism).

From the Pearce link you gave:

Secondly, why is it that, say, an ant colony or the population of China or (I'd argue) a digital computer - with its classical serial architecture and "von Neumann bottleneck" - don't support a unitary consciousness beyond the aggregate consciousness of its individual constituents, whereas a hundred billion (apparently) discrete but functionally interconnected nerve cells of a waking/dreaming vertebrate CNS can generate a unitary experiential field? I'd argue that it's the functionally unique valence properties of the carbon atom that generate the macromolecular structures needed for unitary conscious mind from the primordial quantum minddust.

So I still wonder whether anyone actually believes that you could simulate a human mind with a computer but that it would not be conscious.

Comment author: bogus 25 March 2010 05:54:24PM 2 points [-]

both Searle and Pearce would deny the possibility of simulating a person with a conventional computer.

They would deny that a conventional computer simulation can create subjective experience. However, the Church-Turing thesis implies that if physicalism is true then conscious beings can be simulated. AFAICT, it is only Penrose who would deny this.

Comment author: mattnewport 25 March 2010 06:25:59PM 0 points [-]

Do you mean the Church-Turing-Deutsch principle? It appears to me that Pearce at least in the linked article is making a claim which effectively denies that principle - his claim implies that physics is not computable.

Comment author: bogus 25 March 2010 06:42:51PM 0 points [-]

It appears to me that Pearce at least in the linked article is making a claim which effectively denies that principle - his claim implies that physics is not computable.

Why? Pearce is a physicalist, not a computationalist; he ought to accept the possibility of a computation which is behaviorally identical to consciousness but has no conscious experience.

Comment author: mattnewport 25 March 2010 06:51:18PM 0 points [-]

he ought to accept the possibility of a computation which is behaviorally identical to consciousness but has no conscious experience.

What sense of 'ought' are you using here? That seems like a very odd thing to believe to me. If you think that's what he actually believes you're going to have to point me to some evidence.

Comment author: bogus 25 March 2010 06:54:01PM *  0 points [-]

That seems like a very odd thing to believe to me.

So that means you are a computationalist? Fine, but why do you think physicalism may be incoherent?

If you think that's what he actually believes you're going to have to point me to some evidence.

It's hard to fish for evidence in a single interview, but Pearce says:

The behaviour of the stuff of the world is exhaustively described by the universal Schrodinger equation (or its relativistic generalization). This rules out dualism (casual closure) or epiphenomenalism (epiphenomenal qualia would lack the causal efficacy to talk about their own existence). But theoretical physics is completely silent on the intrinsic nature of the stuff of the world; physics describes only its formal structure.

To me, this reads as an express acknowledgement of the CT thesis (unless quantum gravity turns out to be uncomputable, in which case the CTT is just plain false).

Comment author: mattnewport 25 March 2010 08:01:46PM 1 point [-]

So that means you are a computationalist? Fine, but why do you think physicalism may be incoherent?

The distinction seems to hinge on whether physics is computable. I suspect the Church-Turing-Deutsch principle is true and if it is then it is possible to simulate a human mind using a classical computer and that simulation would be conscious. If it is false however then it is possible that consciousness depends on some physical process that cannot be simulated in a computer. That seems to me to be what Pearce is claiming and that is not incoherent. If we live in such a universe however then it is not possible to simulate a human using a classical computer / universal Turing machine and so it is incoherent to claim that you could simulate a human but the simulation would not be conscious because you can't simulate a human.

To me, this reads as an express acknowledgement of the CT thesis (unless quantum gravity turns out to be uncomputable, in which case the CTT is just plain false).

I honestly don't see how you make that connection. It seems clear to me that Pearce is implying that consciousness depends on non-computable physical processes.

Comment author: bogus 25 March 2010 08:33:42PM 0 points [-]

if it is then it is possible to simulate a human mind using a classical computer and that simulation would be conscious.

You seem to be begging the question: I suspect that we simply have different models of what the "problem of consciousness" is.

Regardless, physicalism seems to be the most parsimonious theory; computationalism implies that any physical system instantiates all conscious beings, which makes it a non-starter.

Comment author: RobinZ 25 March 2010 08:38:46PM *  1 point [-]

[...] computationalism implies that any physical system instantiates all conscious beings, [...]

Say again? Why should I believe this to be the case?

Comment author: Nick_Tarleton 25 March 2010 08:47:09PM *  3 points [-]

Basically, the interpretation of a physical system as implementing a computation is subjective, and a sufficiently complex interpretation can interpret it as implementing any computation you want, or at least any up to the size of the physical system. AKA the "conscious rocks" or "joke interpretations" problem.

Paper by Chalmers criticizing this argument, citing defenses of it by Hilary Putnam and John Searle
Simpler presentation by Jaron Lanier

Comment author: mattnewport 25 March 2010 08:47:06PM 0 points [-]

So do you think there is a meaningful difference between computationalism and physicalism if the Church-Turing-Deutsch principle is true? If so, what is it?

Comment author: bogus 25 March 2010 09:23:59PM *  1 point [-]

So do you think there is a meaningful difference between computationalism and physicalism if the Church-Turing-Deutsch principle is true?

Basically, physicalism need not be substrate-independent. For instance, it could be that Pearce is right: subjective experience is implemented by a complex quantum state in the brain, and our qualia, intentionality and other features of subjective experience are directly mapped to the states of this quantum system. This would account for the illusion that our consciousness is "just" our brain, while dramatically simplifying the underlying ontology.

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