Bruno Marchal wrote:
> Le 26-avr.-07, à 16:31, Juergen Schmidhuber a écrit :
>> Hi Max,
>> in this particular universe it's going well, thank you!
>> As promised, I had a look at your paper. I think
>> it is well written and fun to read. I've got a few comments
>> though, mostly on the nature of math vs computation,
>> and why Goedel is sexy but not an issue
>> when it comes to identifying possible mathematical
>> structures / universes / formally describable things.
>> I think some of the comments are serious enough to affect
>> the conclusions. Some come with quotes from papers in
>> where several of your main issues are addressed.
>> Some are marked by "Serious".
>> I am making a cc to the everythingers, although it seems
>> they are mostly interested in other things now - probably
>> nobody is really going to read this tedious response which
>> became much longer than I anticipated.
> Don't worry, we are used to some long posts in this list. I am not sure 
> you follow the list because the "other things" you are mentioning are 
> just the follow up of the search of the theory of everything, except 
> that since you leave the list, denying the 1-3 distinction, some years 
> ago, most people who continue the discussion now are aware of the 
> necessity to take into account that distinction between first and third 
> person points of view, and more generally they are aware of the mind 
> body problem (or of the 1-person/3-person pov relations). I think most 
> of them, except new beginners, have no more any trouble with the first 
> person indeterminacy in self-duplication experiments, etc.
> I have already made this clear: the hypothesis that there is a physical 
> computable universe (physicalist-comp) is just untenable.
> Let me recall you the reason: obviously physicalist-comp entails what 
> we are calling comp in this list, that is, the hypothesis that "we" are 
> locally emulable by a digital universal machine. I will call it 
> "indexical comp" to insist on the difference. So:
>   Then the Universal Dovetailer Argument shows that comp entails that 
> the physical appearances have to be justified *exclusively* by a 
> self-duplication like first person (plural) indeterminacy: see the pdf:
> The main idea is that INDEXICAL-COMP entails that we don't know which 
> computations support our local states, and that they are a continuum of 
> computational histories (computations + possible "real" oracles) going 
> through those states. 

Exactly how do you mean "continuum"?  Do you mean an uncountably infinite 
number (the power set of the integers)?  Is it a realized infinity or a 
potential one?

>It can be argued that the first person "physical" 
> appearances does emerge from a "sum" on all those computational 
> histories, but only *as seen from those 1-person views*. But this 
> entails that "apparent physical universe" are not necessarily 
> computable objects. Actually, indexical comp entails it exists 
> "exploitable" internal indeterminacies. A priori:
> It gives to physics a more key role than in Tegmark's idea that the 
> physical universe is a mathematical structure of a certain type. Comp 
> (indexical comp) relate somehow physics to almost all mathematical 
> structures (in a certain sense).
> This constitutes the main critic of both your approach and Tegmark's 
> one in the search of a TOE.  You still talk like if the mind body 
> relation was a one-one relation, when the mind can only be associated 
> to infinities of states/worlds. With indexical-comp there is no obvious 
> notion of "belonging to an universe". This has been discussed many 
> times on the list with different people.
> And then, once you realize the fundamental importance, assuming comp, 
> of keeping distinct the possible views that a machine has to have about 
> arithmetical or mathematical reality, 

What is a machine?  Am I to think of it as one of the continuum of histories 
corresponding to a 1st person viewpoint?

Brent Meeker

> and that physics emerges from one 
> such points of view, then it is hard not to take into account the fact 
> that any universal machine looking inward cannot not discover those 
> points of view; indeed  they appear as inevitable modal or intensional 
> variant of the godelian provability predicate. This makes Godel's 
> theorems (and Lob's generalization, and then Solovay's one) key tools 
> for extracting physicalness from number's extensions and their (lobian) 
> intensions. And, and this is a major technical point, it makes this 
> form of comp testable, by comparing the comp-physics with the empirical 
> physics.
> Now I have discovered that those modal variant offer a transparent 
> arithmetical interpretation of Plotinus hypostases. You are welcome in 
> Siena in June where I will present my paper "A purely Arithmetical, yet 
> empirically falsifiable, Interpretation of Plotinus' Theory of Matter":
> I can send you a copy of the paper later for copyright reason. You can 
> also consult my preceding paper:
> Marchal, B., Theoretical Computer Science & the Natural Sciences, 
> Physics of Life Reviews, Elsevier, Vol 2/4 pp 251-289, 2005. Available 
> here:
> Max, Juergen, you are still under the Aristotelian physicalist spell, 
> and you are still putting the "mind-body" problem under the rug, I'm 
> afraid. But I am aware it is a tradition since about 1500 years, when 
> scientists, without much choice alas, did abandon theology to 
> "politicians" ...
> (scientific theology = theology done with the usual doubting procedure 
> of the modest interrogating scientist).
> Juergen, are you still denying the 1-3 distinction (like in our old 
> conversations)?  Are you still thinking  that there is no 1-first 
> person indeterminacy, or that such an indeterminacy has no role in the 
> emergence of the physical laws?  Could you tell me at which step of the 
> UDA you are stuck? (cf the UDA version of the SANE paper, ref above).
> I will asap try to explain the arithmetical version of the UDA, the one 
> based on Godel and which can be seen as an arithmetical interpretation 
> of Plotinus' main "hypostasis" (in case you prefer to read Plotinus 
> instead of doing the duplication thought experiment, UDA, ...).
> Some people asks me to do this without too much technics and I have to 
> think about how to do that. I recall the UDA is already the "non 
> technical" (yet rigorous) argument. The interview of the machine is of 
> course formal and technical, and its only need (beside illustrating the 
> UDA) comes from the desire to *explicitly*extracts the physical from 
> numbers.
> Bruno
> PS This list, wisely unmoderated by Wei Dai, welcomes, for obvious 
> reason giving the hardness and originality of the subject,  both 
> professional and non professional. By professional I just mean people 
> submitting theses, papers or books from time to time, even rarely. So, 
> don't hesitate to send us "call of paper" related with comp and or 
> everything-like or Everett-like TOEs. Thanks. And don't hesitate to 
> participate, 'course!
> > 

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