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
> http://www.idsia.ch/~juergen/computeruniverse.html
> 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:
PHYSICALIST-COMP => INDEXICAL-COMP
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:
http://iridia.ulb.ac.be/~marchal/publications/SANE2004MARCHAL.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. 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:
INDEXICAL-COMP entails NOT PHYSICALIST-COMP.
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, 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":
http://www.amsta.leeds.ac.uk/~pmt6sbc/cie07.html
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:
http://linkinghub.elsevier.com/retrieve/pii/S1571064505000242
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!
http://iridia.ulb.ac.be/~marchal/
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Received on Mon Apr 30 2007 - 10:04:11 PDT