Hi Godfrey,

Le 17-août-05, à 19:20, [EMAIL PROTECTED] a écrit :

[BM]
Not really, as far as you agree that classical physics can be extracted from quantum physics. My favorite unrigorous way: Feynman integral (see my paper:
http://iridia.ulb.ac.be/~marchal/publications/CC&Q.pdf
for a little summary.

Bruno

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

[GK]
I did not say, nor do I believe, that one can extract the "classical world" from QM, as I pointed out to Lee,


OK. Now I agree with Lee, and many on the FOR and the Everything lists that Everett (many-worlds + decoherence already) constitutes a "solution of the measurement problem". All measurements are just interaction, and then all states are relative. As I said, it seems to me that this is even more clear in the integral formulation of QM where F = ma can be deduced from the "sum on all histories". But this is going a little bit out of topics, and is not needed to understand the comp derivation. We can come back on this latter.




but one can surely object to a "third party" theory from the fact that it does not reproduce a classical world any better than quantum
mechanics. This is a complicated issue because:

(a) Classical physics does not explain the "classical world" either as it cannot account for the stability of matter, for instance,
which only QM explains.
(b) Quantum mechanics predicts some entirely macroscopic phenomena that we do observe as part of the "classical world" i.e. superfluidity of He, superconductivity, stability of the vaccuum etc...



OK.





In other words: if I found a way of shooting down your theory in a way that would not obviously violate the correspondence limit of QM , it would shot down! That is what I am suggesting above. But do not worry because I think you are a lot better
shot by QM.



To anticipate a little bit, I think this will be hard. From comp you can deduce quickly the qualitative "many-relative state/worlds" feature, the no-cloning theorem, the appearance of indeterminacy. I told you Newtonian physics (with a single universe-history) would cause much more problem to my approach.







Now my logistic COMPlaints about your COMP:

I have searched through your web site to see whether I could find a full statement of your hypothesis since you were not kind enough to reproduce it in the previous exchange. I don't read French that well and your English paper is somewhat
sketchy on this, so I can only refer to what you state in the page :

http://iridia.ulb.ac.be/~marchal/publications/SANE2004MARCHAL.htm

where I found what looks like a definition. My first objection is to the following sentence:

"Definition: Classical Digital mechanism, or Classical Computationalism, or just comp, is the conjunction of the following three sub-hypotheses:"

after which you list three items which I will not reproduce here and will just short as 1) YD for "Yes-doctor", 2) CT for
Church Thesis and 3) AR for Arithmetic Realism.

My objection is that of these three only the first can genuinely be called an hypothesis!



Ouh la la. You are close to the 1004 fallacy (asking for more precise definition than the reasoning itself). At the start you can use the term "axioms", "postulates", "theses", "premises", "assumptions", "hypotheses", etc.. in a similar way.




CT, as the name indicates, is a Thesis which is most likely unprovable but favored by overwhelming heuristic support.


Not only overwhelming supports: there is the deep conceptual argument that Kleene has discovered when he failed to refute Church's "definition" of the computable functions. The argument is the closure of the set of partial computable functions for the most transcendental mathematical operation: diagonalization. Kleene invented the vocable "Church thesis". The first to get Church's thesis is Emil Post (in the early 19-twenties).

See (perhaps later) the diagonalization posts in this list (mentionned in my web page).



 I know that there are
some people in the southern hemisphere who think that QComputation could produce a counterexample to shoot it down (and perhaps it could) but you and I agree that it is unlikely.


OK.



And AR is a metaphysical position which I
happen to subscribe but which I would never fathom to try and prove or empirically test (nor do I have any idea
on how to do it! Do you?)


Well, I have decided to put it explicitly, because, in front of my reasoning, some people cop out simply by saying "Ah, but you are a platonist!". So I prefer to say it at once. I agree with you it is a sort of "cop out". Now, although 99,99999999 % of the mathematician are platonist during the week, most like to pretends they are not (the week-end!).





Now I suppose that you need for these three things to be true for the rest of your argument to go. But I find that it is extremely unfair to force your most excellent hypothesis YD to have to stand in company of the other two to assert
its merits!!! In other words as

(1) YD is obviously independent from CT and AR


'course.



(2) CT and AR stand no chance of being falsified empirically (or we both like them that way, which is the same).


I give the opportunity to make comp false in more than one way. If you read the Maudlin paper, you will see that he consider the YD doctor (or equivalent) as tautologically true (unlike the functionnalist hypothesis). This is due to the fact that, unlike many older computationalist or mechanist, I put no bound on the low-levelness of the substitution level. I can say yes to the doctor provided that he simulates my brain at the chromodynamical level, including all partiocles having interacted with any other particles in the past (in which case my brain is the "physical universe" itself. My brain could be a quantum computer, without violating comp. The no-cloning theorem does not interfere.



(3) No one that we know has been able to extract conclusions such as yours from CT & AR without YD (right)


This is a subtle question. The *necessity* of the reversal is hardly understandable without the YD assumption. But once you grasp the necessity of the reversal, then the very derivation of natural science from computer science does not use it at all. Indeed the cognitive science's "grand-mother" is completely substituted by the Lobian Machine at this stage. So, with OCCAM razor, once enough of physics is derived, you can eliminate the grand-mother and the whole YD assumption. Some mathematician asked me to put the UDA argument under the form: motivation", and to state that my real "scientific" hypothesis are CT and AR. I find that dishonest and misleading, because, without understanding the necessity of the reversal, the interview of the Lobian machine would resemble to nothing but a little piece of pure mathematics, especially given that I have until now extracted to few real physics to really call OCCAM. All my papers introduce the grandmother (and YD), and then translate the argument in the Lobian language. But then if the logics of the observables that I have derived from comp (at the necessary place) appears to be von Neumann Quantum logics, I know people will eliminate the grandmother and the YD, for bad reasons (They want pure math, they hate cognitive science, etc.). My fear is that people take the epistemological elimination of the grand-mother (and the YD assumtion) as an ontological elimination of the first person, and nothing could be more wrong than that.
See the footnote 3. in the SANE paper, and the text



would you have any objections to us concentrating, from here on, on your "YD hypothesis"?


I have no problem with that. I am willing taking full responsability for the YD hypothesis, even if at some points we can forget it, as I explain above.




I am saying this because I actually think that it is the real interesting and original part of your proposal



Actually I agree. But the YD hypothesis with fixed (high) level of substitution is the everyday bread of cognitive science since Plato.




and it does not
need those two other huge "body guards" which I happen to be friends with. OK?


OK.




If you agree with this I may have something interesting to tell you about your idea that you have not anticipated!


I'm very curious!




Please,don't COMP out! Say "yes", Doctor Bruno!


Well, the real Doctor is Stathis Papanoiannou, in this list ;-)

Let me comment your last post also.




Thanks for your assent on this. I am sure that CT and AR are needed, at some point, for your really outrageous conclusions. But I am sure you agree that they cannot save them if the "Yes doctor" presumption can be shot down by itself. Right?


So, I repeat because it is a difficult point. Strictly speaking I don't need the YD (Yes Doctor) hypothesis to get physics from comp, because I just interview a lobian machine on its consistent extension. But I need it to explain why it must be so, and make explicit the link with cognitive science, psychology, theology ....



This would save me from having to read through your Dovetail-Lob etc... argument which
is probably way above my head!


Please don't feel obliged to follow the argument. Do it if you really want to find what is wrong in the path toward the "outrageous conclusion". I mean that the Universal Dovetailer Argument is much more simple than some people imagine, although many remain unaware that the real difficulty is in the "movie graph" part. OK: cognitive science is not easy. For the second part, the interview of the universal lobian machine, the difficulty resides in understanding some amount of computer science, logic and logics, and quantum physics. I prefer the slow but sure path, take your time, I'm patient: you can ask me questions in my next life ;-)



We obviously move in very different circles because I was taught by very stubborn old strong AI types and cognoscendi cognitivists and I have never heard anyone argue for something like that YD hypothesis!


Glad you notice. although the idea is defended and attacked since Plato, I am perhaps the first to tackle it in a hypothetico-deductive way. But then I'm lucky being born after Godel and Lob. (Which "I"? I don't know).



But as you have conceded no one
needs it to defend the old-fashioned materialist functionalism credo that you (and I) do not subscribe to anyway.

OK,

Now tell me what I didn't anticipate from YD, I'm very curious :)
And please feel free to shot down my work in any way. It is the best way for me to illustrate the solidity of my argumentation :) ... and who knows ? perhaps you will find an error or some awkwardness. I would appreciate and acknowledge.

Bruno



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


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