On 04 Mar 2012, at 01:14, meekerdb wrote:

On 3/3/2012 12:43 PM, Bruno Marchal wrote:

comp can never be proved


or disproved

False. By UDA.

so there is no point in worrying about it. I just assume it's true because I could not function otherwise

Which is a nonsense. Nobody use the hypothesis that the brain is a machine in their everyday life. If tomorrow comp is refuted, you will not feel a difference. Just that both matter and mind will be more mysterious.

In fact most people are unreflective dualists. They assume they have a magic soul so that if their brain were replaced by a computer 'they' would become a philosophical zombie while their 'real self' would be teletransported to heaven (or Platonia if they happen to be mathematicians :-) ).

Yes. I agree. Many people are instinctively skeptical for comp, unless they are molecular biologists. Note that this is already explained in the modal logic of self- reference: machine cannot know that they are machine, and they cannot believe it either. Comp is necessarily (provably) counter-intuitive. There is a natural tension between the hypostases S4Grz1 and G1, G1*, Z1*, X1*. The self-referentially correct machine cannot avoid a conflict between any third person account of itsel (G1) f, and its 1p "intuition" (S4Grz1).

On 3/3/2012 12:43 PM, Bruno Marchal wrote:

I understand that seems possible. That is why I avoid in the thought experience, both amnesia, death, or anything which would prevent the persons, before he opens the reconstitution box, in W and M, to feel any different from the person in Helsinki, apart from finding themselves in a box, and not knowing where they are. In such case, to believe that you don't survive would prevent you to believe that you can survive teleportation, and comp would be refuted.

But that seems to be equivocation on 'you'. 'I' have a certain continuity of thought and more distant memories. The hypothetical teleportation would necessarily (nomologically) produce a discontinuity in thought, so my identity would depend on my memories.

The equivocation of "I" is well illustrated by the duplication, made possible by comp. But the problem is avoided in the definition of comp by the quasi-operational "yes" doctor. (It is not entirely operational because logically a zombie can also say "yes" to the doctor, but of course we assume *you* are not a zombie).

Small changes in memory would still allow 'me' to identify myself with the Helsinki person, but large ones, e.g. I remember living in Brussels not Helsinki, would make 'me' a different person.

Sure. But, by construction, there are no change at all in the memories. The personal memories are annihilated and reconstituted integrally.

'I' am an inference, or a construct, from my memory (including unconscious habit/memory).

Not only that. "you" are also a universal number/machine. It is more ""I"" which is an inference than "I". The real first person, captured by Theatetus, is really where ""I"" and "I" intersect, so to speak.

So the question as to which probability I have finding myself in M or W is ill posed;

Here I strongly disagree. Despite what you say above, the question is well posed. The candidate in Helsinki has all the information needed + his assumption that comp is correct, which is part of the inference. He knows in advance that he will be reconstituted in both W and M. He knows with certainty (with respect to his comp assumption) that in both W and M he will find himself to be in one place, and that he cannot know which one in advance without adding a magic ability contradicting comp. The question bears explicitly on its singular future personal experience, and in this situation, the question is as mundane than any question about a well defined random variable. The duplication will be, from its first person perspective, equivalent with a Bernouilli experience, despite the equivocation of the "I". That's why we do such experience, to avoid any problem due to the "I" equivocation. All we need is to define the 3-I by the body described at the right level, and the 1-I, which in UDA is nothing more than the personal memory, which is supposed by construction to be not altered in the annihilation/reconstitution move.

it assumes that there is one 'I' and we can ask where this 'I' finds himself. But there is no 'I' in this sense.

Of course there is such an "I". Once your body has been reconstituted in both place, they both knows very well where that "I" feels to be, and this is known in advanced (believed and true, given that we assume the candidate believe in comp and that comp is true). Such an "I" is well defined. It is the owner of the memory together with the fact that those memory are known true, by us. It is as well defined as in any mundane question like "Where will I see the needle of my measuring device apparatus?" in any experience of physics. The question is well defined as long as we suppose comp true.

I don't think that affects the idea of 1p uncertainty though. If you believe QM is correct you already believe there is 1p uncertainty; even if you like Copenhagen.

Without the collapse, the quantum uncertainty is entirely explained by the relative comp 1-indeterminacy. With the collapse it is the complete mess, because we have to assume QM is false for the observer, and this reintroduce a form of unintelligible dualism. Copenhagen is a label for more than hundred of failed and incompatible attempts to avoid parallel universe, but with comp we know that we cannot avoid them by pure logic and arithmetic.



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