Hi Greg,

On 15 Jun 2008, at 10:40, Greg Egan wrote:

>> My attributes (eg
>> height, weight and so on) are all drawn from distributions of such
>> attributes. Why not some hypothetical property like "observer class"
>> as set up in this toy problem?
> Why is your height and weight drawn from a certain distribution?  It's
> because you've been exposed to certain statistical influences on those
> attributes, and those influences are influences that you have in
> common with a certain subset of the human population.  But it would be
> absurd to say that *your* height and weight is drawn from the
> distribution of heights and weights of all living creatures in the
> history of the universe.  Equally, it would be absurd to say that your
> observer class has been drawn from the distribution of all observers
> in the history of the universe.

I agree, and I think one half of the everything-list participants  
agree on this (cf our Relative versus Absolute Self-Sample Assumption  
debates). The probabilities are relatively conditioned on the "brain/ 
body" states  *histories*, and things are not so different from  
Feynman integral formulation of QM.
Now, the question is "why *quantum* histories". My point is that if we  
assume we are turing-emulable, then the probabilities have to be  
derived from a sum on *all* computations. Not just the quantum one.  
This means we can test the computationalist theory by comparing the  
sum on all quantum histories/computations (with its weird probability/ 
amplitude relation) and the sum on all histories/computations.
At first sight the comp theory is false because it leads to many more  
white rabbits than the quantum, but by taking into account constraints  
related to incompleteness phenomena and logic of self-references,  
there are (rather technical alas) evidences that the third person  
white rabbits go away too.
It remains abnormally too much first person white rabbits, and I am a  
bit stuck on that. QM, and physics in general, per se, does not even  
address those first person purely qualia rabbits (although Galileo,  
Einstein, Boscovitch, Everett, .Wheeler, Rossler, ... can be seen as a  
sequences of physicists converging to that.
Assuming we are turing emulable, we have to "radicalize" Everett. We  
have to justify why, in appearance, the QM computations wins in the  
observable game. All the pieces of the puzzle are there.

Greg, I have read and appreciate very much your "Permutation City"  
novel, but to be honest, I see you still believe "physics" study what  
there is. This seems to prevent you to follow your own logical line.  
See my Sane04 paper for an argument (in english) showing that IF we  
are turing emulable, THEN the observable is just what emerges from all  
possible local merging and differentiations of computational histories  
(= as seen as first person point of view, probably plural first  
person. Merging works through amnesia, and I don't explicitly tackle  
merging in my publications).

In "Laws without Laws", or "It from bits" John Archibald Wheeler got  
that point: the physical laws emerges on something non-physical.  
Assuming we are digital machine, that non-physical stuff has not to be  
more than the additive and multiplicative properties of natural  
numbers. Poetically: what we take for being the physical reality is in  
fact the border of the ignorance of self-introspecting universal  
machine/number ("us"). That "Ignorance" is *very* big, and productive,  
almost "alive" when seen from inside. And mathematically tractable by  
computer science/recursion theory.
To sum up in a Soccer way: Plato 1, Aristotle 0.  (I don't pretend the  
match is over!)

But I think a lot that QM confirms already the comp hypothesis, and  
the non-materiality of matter.
To sum up in a Kronecker's way: God creates the natural numbers, all  
the rest are web of coherent (and less coherent) dreams by natural  
I think I have an argument showing that the comp hyp reduces the mind- 
body problem into a pure body problem. The problem now is that most  
physicist takes bodies from granted, and this prevents the  
understanding of the argument. But that is "religion".
(For example, Vic Stenger in his "God, the failed hypothesis"  
identifies material with natural, and immaterial with supernatural,  
making math and logic, what? parapsychology? Theology perhaps. At  
least physicists like Penrose, Wheeler, Deutch, Tegmark are aware of  
the mathematical reality. Only logicians seems to be aware of (and  
familiar with) the intricacy of digital self-reference. It is pity  
that the gap between logicians, physicists and philosopher of mind/ 
theologian remain so wide.  At more than one level, I'm afraid. I am  
quite opposed to creationism and any "authoritative" bible-god  
crackpot theology, but many scientists aggravate the hiatus by being a  
bit dogmatic on matter like if we would have solved the mind-body  
problem. My modest work, and our discussions here, just points toward  
a "scientific" formulation of that old problem.
Some believe that science is ending. I believe that it has not yet  
begun (abstracting from -500 to +500 perhaps ...)

Best regards,



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