On 10 Aug 2009, at 09:08, Colin Hales wrote:

> Bruno Marchal wrote:
>>
>>
>> On 06 Aug 2009, at 04:37, Colin Hales wrote:
>>
>>> Man this is a tin of worms! I have just done a 30 page detailed  
>>> refutation of computationalism.
>>> It's going through peer review at the moment.
>>>
>>> The basic problem that most people fall foul of is the conflation  
>>> of 'physics-as-computation' with the type of computation that is  
>>> being carried out in a Turing machine (a standard computer). In  
>>> the paper I drew an artificial distinction between them. I called  
>>> the former NATURAL COMPUTATION (NC) and the latter ARTIFICIAL  
>>> COMPUTATION (AC). The idea is that if COMP is true then there is  
>>> no distinction between AC and NC. The distinction should fail.
>>
>> Why? COMP entails that physics cannot be described by a  
>> computation, but by an infinite sum of infinite histories. If you  
>> were correct, there would be no possible white rabbit. You are  
>> confusing comp (I am a machine) and constructive physics (the  
>> universe is a machine).
>>
>>
> This is the COMP I have a problem with. It's the one in the  
> literature.  It relates directly to the behaviour (descriptive  
> options of) of scientists:
> COMP
>
> This is the shorthand for computationalism as distilled from the  
> various sources cited above. The working definition here:
>
> “The operational/functional equivalence (identity,  
> indistinguishability at the level of the model) of (a) a  
> sufficiently embodied, computationally processed, sufficiently  
> detailed symbolic/formal description/model of a natural thing X and  
> (b) the described natural thing X”.
>
> If this is not the COMP you speak of, then this could be the origins  
> of disparity in view. Also, the term "I am machine" says nothing  
> scientifically meaningful to me.

This is not comp. Actually the definition above is ambiguous, and  
seems to presuppose natural things.

I use comp in its older and standard sense in the cognitive science.  
"I am a machine" has the advantage of having an operational meaning by  
entailing the possible use of artificial brain. If you give a meaning  
to the word "consciousness", comp is the assertion that consciousness  
is an invariant for a precise set of transformation.




> The term "The universe  is a machine" also says nothing  
> scientifically meaningful to me.

Well comp, in its indexical sense, entails "the universe is a machine"  
is inconsistent.


>
>
> I offer the following distinction, which relates directly to the  
> human behaviour (observable, testable) called scientific behaviour.
> (a) scientific descriptions of a natural world produced by an  
> observer inside it, built of it. (science currently 100% here)
> and
> (b) scientific descriptions (also produced inside it by (a) human  
> observers) of a natural world as a natural form of computation which  
> produces the above observer.(science currently Nil% here for no  
> justified reason)
> and
> (c) The natural world as an actual instantiation of (b)."Whatever it  
> is that we find ourselves in".
>
> When you utter the word "physics" above, I hear a reference to  
> descriptions of type (a) and nothing else. I assume no direct  
> relationship between them and (b) or (c). The framework of (a), (b), 
> (c) is all that is needed, justified because it exhausts the list of  
> possible views of our situation which have any empirical/explanatory  
> relevance. None of the descriptions (a) or (b) need be unique or  
> even exact. The only thing required of (a) is prediction. The only  
> thing required of (b) is prediction of an observer who is  
> predicting. Both (a) and (b) are justified empirically in predicting  
> a scientist.
>
> Now consider the ways I could be confused:
> (i) computed (Turing) (a) is identical to (c) (all of it)
> or
> (ii) computed (Turing) (b) is identical to (c) (all of it)
> or
> (iii) computed (Turing) (a) of a piece of (c) is identical to the  
> piece of (c) within (c)
> or
> (iv) computed (Turing) (b) of a piece of (c) is identical to the  
> piece of (c) within (c)
>
> The COMP I refute above is of type (iii). I did not examine (iv) in  
> the paper.
>
> (iii) is the delusion currently inhabiting computer science in  
> respect of AGI expectations. The 'piece of (c)'  I use to do this is  
> 'the human scientist'. It is expectations of AGI projects that I  
> seek to clarify - my motivation here. It is a 100% practical need.
>
> (i) and (ii) might be possible if you already knew everything....but  
> that is of no practical use.
> (iii) and (iv) viability depends on the "piece of (c)/rest of (c)"  
> boundary and how well that boundary facilitates an AGI.
>
> So... who's assuming stuff? :-)
>



But then your "non-comp" is a direct corollary of UDA. If we assume  
there is a "natural world", or a "primitive physicalness", comp, in  
the sense of INDEXICAL digital mechanism (and "indexical" refers to  
the use of "I" in "I am a machine") is false.

You can sum up the UDA conclusion by: If I am a machine then  
observable Nature is not.

I agree that brain does not do computation, if only because brains  
does not exist primitively, a physical brain is a projected  
theoretical construction. It is a projection of an non enumerable set  
of arithmetical computations, and comp predicts that if we look  
closely enough to that brain, or to its neighborhood we will see ...  
well, what quantum mechanicians have already discovered: infinities of  
coherent computational histories.

Anyone believing in a natural world must understand that they cannot  
be machine, and thus the natural world cannot be a machine either.
Note this:
Indexical comp entails nature is not mechanical (nor primitive)
Non indexical comp entails nature is not mechanical.

So, with or without comp, observable nature cannot be described by a  
computation. Constructive physics is an inconsistent idea. This does  
not mean that constructive physics cannot have some application, but  
it is useless for searching a TOE or for having any bearing on  
fundamental matter (unless you accept person eliminativism).

It seems that your critics bear on constructive physics. Then we  
agree. Without QM, I would have believed that UDA is a refutation of  
indexical comp.

Colin, in this list, since ten years, and in the literature,  
computationalism has always been the indexical digital mechanist  
thesis. I propose you use another term for the non indexical comp  
thesis.

Bruno



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




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