On Sun, Oct 02, 2011 at 01:42:19PM +0200, Bruno Marchal wrote:
> Hi Russell,
> 
> 
> On 02 Oct 2011, at 11:37, Russell Standish wrote:
> 
> >In David Deutsch's Beginning of Infinity chapter 8, he criticises
> >Schmidhuber's Great Programmer idea by saying that it is giving up on
> >explanation in science,
> 
> Actually I did address this point on the FOR list years ago.
> Somehow,  I share David's critics on Schmidhuber's idea of a great
> programmer when seen as an *explanation* (of everything). My (older,
> btw) publications makes this point clear.  The Universal Dovetailer
> (which can be seen as an effective and precise version of the "great
> programmer", and which is a tiny part of elementary arithmetical
> truth) makes it possible to *formulate* (not solve!)  the mind body
> problem mathematically, but Schmidhuber use it as an explanation
> gap. He missed the fact that if we are machine we cannot know in
> which computations we are and we have to recover the physical laws,
> not from one computation but from an internal (self-referential)
> statistics on infinities of computations, and that statistics has to
> be recovered entirely from the self-reference ability of machine.

Sure - Schmidhuber, with his speed prior, assumed that the specific
implementation of the universal reference machine has physical
consequences, but we, thanks to your work, know better.

David's criticism was quite specific - because the specific
implementation of the UTM doesn't have any physical consequences,
therefore one is somehow giving up on obtaining the ulimate
explanation. My response was that surely the question becomes
uninteresting (David's terminology) - or even meaningless (as you state below).

... snip ...

> But this was an answer to David's remark that "the great
> programmers" explains too much, and so don't explain anything. 

I'm aware of this criticism, which applies to ensemble theories in
general. IMHO, the only way to address that critique is with some sort of
observer-relative anthropic selection - but that is a whole other topic!

> 
> >as the hardware on which the "Great Program"
> >runs is unknowable.
> 
> Of course the contrary is true. If we are machine, we know (up to
> some recursive equivalence) what runs us, and where the possible
> hardware come from. Any first order specification of any universal
> machine or theory will do the job. I use elementary arithmetic
> because we are all familiar with it. The laws of physics cannot
> depend on that choice.

We're actually saying the same thing here.

> >
> >David, why do you say that? Surely, the question of what hardware is
> >implementing the Great Simulators simply becomes uninteresting,
> >much like
> >the medieval arguments about the number of angels dancing on the head
> >of a pin. It is unknowable, and it doesn't matter, as any universal
> >machine will do.
> 
> I disagree with this. The notion of primitive hardware is precisely
> shown to be meaningless. The laws of physics are shown to be machine
> independent. Eventually the initial universal system plays the role
> of a coordinate system, and the laws of physics does not depend on
> it.

Isn't this stating the above in a stronger form? "Meaningless", rather
than "unknowable"?


-- 

----------------------------------------------------------------------------
Prof Russell Standish                  Phone 0425 253119 (mobile)
Principal, High Performance Coders
Visiting Professor of Mathematics      hpco...@hpcoders.com.au
University of New South Wales          http://www.hpcoders.com.au
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