Gilles Henri: >If you admit that the others and the external environment do not really >exist, it is difficult to understand why "they" (more precisely, the >representation we have from them) should obey precise laws, even >statistical. That's what I tried to develop in the next paragraph.

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Bruno Marchal: I just believe that with comp, "materiality" doesn't exist objectively. Of course I believe in others ... GH >The point is that I don't see what should oblige the matter to obey precise >laws, if we are not "really" made of it. In other words, why should a >"conscious computation" exist only if it implements some representation of >mathematical laws? BM: Because "computation" obeys to the law of computation, which are subject to theoretical computer science. Mathematics appears here. Consciousness appears when machines infer non communicable truth ... GH: >As a matter of fact, most of our conscious activity does NOT rely on >mathematical laws (or mathematical representations of physical laws). BM: I disagree. See above. GH: >For >me it proves that the representation of physical laws is not NECESSARY to >consciousness. BM: I agree. GH: >It could be then a question of probability, but I don't see >why the number of computations implementing precise physical laws should be >much greater than the number of computations not implementing then - in >fact I would think just the opposite. BM: That is why the computations implementing consciousness MUST, if we keep all along the hypothesis of computationnalism, implement not only precise physical laws, but, precisely, kind of QUANTUM physical laws, which multiply possible futur histories. GH: >I would think that the "UD" is much larger than the DeWitt-Wheeler >equation, so it can describe also a huge number of universes without any >reasonable relationship within it. > >I'll try to put it in more quantitative form. I assume I can give a >"measure" of the set of possible Universes and separate it into three >classes: >A : the subset of universes without conscious beings >B : the subset of universes containing SAS apparently observing a >environment without physical laws. >C : the subset of universes containing SAS apparently observing a >environment with physical laws. > >It seems that we live in a C-Universe. Why? > >I guess (I may be wrong) that if you POSTULATE the existence of a reality >obeying physical laws, you could hope to demonstrate >m(A)>>m(C)>>m(B), >because it is very improbable that conscious beings doing repeated physical >experiments would be unable to unveil the existence of physical laws (for >example by finding systematically very improbable results where the >statistical distributions predicted by QM are never recovered). >The observation of A is excluded by the (generalized) anthropic principle, >so we explain satisfactorily why we see "C". > >However, I think that the "everything computable is realized" hypothesis >would predict m(A)>>m(B)>>m(C), and so the reason why we are in C is much >more mysterious with this hypothesis. Of course if you think you can >justify also m(C)>>m(B) with comp, it would have the bonus to explain why >physical laws exist (which must be postulated in the first stage), but I am >really not convinced of that. My feeling, Gilles, is that you have an excellent understanding of my point. Now, for some reason you don't believe in comp, and for that reason, you take my counter-intuitive result as an opportunity to throw away the comp hypothesis. Honestly that is a little too premature for me. But I'm very glad you realise the bonus: an explanation of the origin of physical laws. But indeed, with comp (which is admitted by numerous people including Schmidhuber, Deutsch, all cognitive scientist, etc.) we must justify why m(C) >> m(B). I don't pretend it is easy. I feel it worthwhile. You can try to prove that comp => m(C) << m(B). In that case, comp will be refuted, once and for all. You can try to prove that comp => m(C) >> m(B). In that case, you will solve the mind body problem and the problem of the origin of the physical laws. BTW, is it clear that with the quantum MWI we have prove that m(C) >> m(B). I guess the decoherent approach has put some light on that problem. But here too, it is still not clear how far we are from a clearcut solution... Bruno.