Dear Jesse,
Would it be sufficient to have some kind of "finite" or "approximate"
measure even if it can not be taken to infinite limits (is degenerative?) in
order to disallow for "white rabbits"? A very simple and very weak version
of the anthropic principle works for me: Any observation by an observer must
not contradict the existence of that observer.

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I disagree with David's claim that "The universe doesn't depend on the
rock for its existence..." since the notion of quantum entanglement, even
when considering decoherence, implies that the mere presense of a rock has
contrapositive effects on the whole of the "universe". The various
discussions of "null measurements" by Penrose and others given a good
elaboration on this.
To me the computational question boils down to the question of how does
Nature solve NP-Hard (or even NP-Complete) problems, such as those involved
with "protein folding", in *what appears to be* polynomial time.
Stephen
----- Original Message -----
From: "Jesse Mazer" <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Wednesday, January 07, 2004 11:36 PM
Subject: RE: Is the universe computable?
> David Barrett-Lennard wrote:
> >
> >Jesse Mazer wrote,
> >
> > > Isn't there a fundamental problem deciding what it means for a given
> > > simulated object to implement some other computation?
> >
> >Yes, but does this problem need to be solved? I have no problem with
> >the idea that some "physical object" (in one computation) can be
> >"interpreted" in all sorts of ways - depending on how you map it. Does
> >it matter if there exists a (weird) mapping between a rock and a
> >universe with conscious inhabitants? The universe doesn't depend on the
> >rock for its existence so who cares!
> >
> >- David
>
> I think it would matter if you want to find the measure of various types
of
> observers/observer-moments--you need to know which ones are instantiated
> more often in the set of all possible computations (to address this you
> might also need a measure on all possible computations). Without some type
> of measure, there is no way to solve the "white rabbit problem".
>
> --Jesse