Comments interspersed.

On Sun, Jan 18, 2004 at 07:15:45AM -0500, Kory Heath wrote:
> 
> I understand this perspective, but for what it's worth, I'm profoundly out 
> of sympathy with it. In my view, computation universality is the real key - 
> life and consciousness are going to pop up in any universe that's 
> computation universal, as long as the universe is big enough and/or it 
> lasts long enough. (And there's always enough time and space in the 
> Mathiverse!) 

Computational universality is not sufficient for open-ended evolution
of life. In fact we don't what is sufficient, as evidenced by it being
an open problem (see Bedau et al., Artificial Life 6, 363.)

I also suspect that it is not necessary for the evolution of SASes,
but this is obvious a debatable point.

> (countably?) infinite. So why would I be more likely to find myself in one 
> of those universes rather than the other?
> 
> -- Kory
> 

The issue of where physics comes from is addressed in my paper "Why
Occams Razor". Dynamics on complex-valued hilbert spaces is the most
likely observed universe. I have just had another discussion with
Stephen King re why we should observe 3+1 spacetime. I am somewhat
unconvinced like you by the arguments put forward in Tegmark's paper
(which aren't due to him at all), but at present its the best we
have. There should be an anthropic reason why 3+1 spacetime is
necessary, or even the most likely dimensionality seen by observers.

                                                Cheers


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