On 12 Aug 2011, at 18:56, meekerdb wrote:

On 8/12/2011 2:00 AM, Bruno Marchal wrote:


On 11 Aug 2011, at 19:24, meekerdb wrote:

On 8/11/2011 7:14 AM, Stathis Papaioannou wrote:

In any case, I have made the thought experiment simpler by *assuming*
that the replacement component is mechanically equivalent to the
biological tissue. We can imagine that it is a black box animated by God, who makes it tickle the surrounding neural tissue in exactly the right way. I think installation of such a device would *necessarily*
preserve consciousness. What do you think?


Are you assuming that there is no "consciousness" in the black box?


The problem is there. In fine, if the brain works like a machine, consciousness is not related to its physical activity---which is a sub level notion, but to the mathematical relation defining the high level computation leading to the subject computational state.

A related problem: is the back box supposed to be counterfactually correct or not, or is the black box accidentally correct for one execution. Answering that question in keeping the mechanist assumption leads to the "in fine" just above.

I think we are close to the question: does comp entails the 323 principle?

Right. If you idealize the brain as a digital computer then it seems that register 323 is unnecessary.

Ah! Nice. But then comp makes physics a (very precise and constrained) branch of machine's self-reference theory. Well, you cannot say that comp idealizes the brain as a digital machine. It makes the brain physically replaceable by a digital computer with you not noticing any difference.



But the brain, like every thing else, ...

like every physical object (I guess)



 ... is a quantum object

Very plausibly. OK.



and it is characteristic of QM that possible interactions that don't occur make a difference.

Yes. This is made clear by Hardegree's work on quantum logic. Quantum logic's sazaki hook makes it a logic of counterfactual. But the Bp & Dt logics too. And ... but I see that you foresee the objection:



Of course you may object that QM can be computed by a (classical) digital computer -

Yes. So even if the brain is a quantum computer (contra Tegmark, and you, actually), this would just push the 323-principle on a lower level.



but that's on true on in an Everttian interpretation.

Yes. And Everett's interpretation is the only one coherent with comp, indeed. In both direction. Comp can be seen as a generalization of Everett: comp provides a first person account of the collapse and the swe (if the swe is correct).



The digital computer can't compute which interactions occur and which don't; that probabilistic.

In copenhagen theory, or in the GRW theory. Well, in all those non sensical theories. To be short.



All it can do is compute the probabilities for all the possible outcomes, *inculding* the 323 ones.

But only on the level where the quantum brain operates. In the UD*, all level are simulated, so that would not change the "arithmeticalist" ontological conclusion.




I don't insist on that, but it is a key to get the *necessary* ontological reduction to arithmetic (which does not entail an epistemological reduction).

I agree with what you say in another post: the term "behavior" is ambiguous. The notion of substitution level disambiguates a part of it, and the notion of counterfactuality disambiguates an orthogonal part of it.

Am I right in thinking that the counterfactuality includes *everything* that didn't happen?

Every possible inputs, yes.



I'm not sure that's a coherent concept.

Well, the UD will generates those counterfactuals, and we have to show some of them relatively rare. You can certainly conceive that your inputs might be chosen randomly (including the skin inputs). That refers still to very huge but finite numbers.

Now, I don't think the doctor has to do an artificial brain equivalent to mine satisfying *all* counterfactuals. He might as well suppress 'register' that are no more needed (like those perhaps related to childhood's needs or something like that). This is certainly the case if you agree that comp entails the 323 principle. But then ... the coupling realities/consciousness emerges from addition and multiplication, only, by the movie graph (or by Maudlin's argument). If you agree that the physical activity for one specific computation is enough, then consciousness cannot be associated with the physical activity, and only to the (abstract, arithmetical) computations. Jacques Mallah tried coherently, sometimes ago on this list, to block the movie graph argument by attempting to define a physical notion of counterfactuals, but this needs to believe that comp does not entail the 323-principle, even if the brain is a quantum computer, which I find doubtful.

Bruno


http://iridia.ulb.ac.be/~marchal/



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