Re: Is the universe computable

From: Kory Heath <kory.heath.domain.name.hidden>
Date: Tue, 27 Jan 2004 01:19:39 -0500

At 1/26/04, Stephen Paul King wrote:
>The modern incarnation of this is the so-called
>4D cube model of the universe. Again, these ideas only work for those who
>are willing to completely ignore the facts of computational complexity and
>the Heisenberg Uncertainty principle.

I think you and I are living in two completely different argument-universes
here. :) I'm not arguing that our universe is computable. I'm not arguing
that our universe can definitely be modeled as a 4D cube. I'm not arguing
that only integers exist. The only reason why I keep using CA models is
that they're extraordinarily easy to picture and understand, *and*, since I
believe that SASs can exist even in very simple computable universes like
CAs, it makes sense to use CA models when trying to probe certain
philosophical questions about SASs, physical existence, and instantiation.
Quantum physics and the Heisenberg Uncertainty principle are simply
irrelevant to the particular philosophical questions that I'm concerned with.

Forget about our own (potentially non-computable) universe for a second.
Surely you agree that we can imagine some large-but-finite 3+1D CA (it
doesn't have to be anything like our own universe) in which the state of
each bit is dependent on the states of neighboring bits one tick in the
"future" as well as one tick in the "past". Surely you agree that we could
search through all the possible 4D cube bit-strings, discarding those that
don't follow our rule. (This would take a Vast amount of computation, but
that's irrelevant to the particular questions I'm interested in.) Some of
the 4D cubes that we're left with will (assuming we've chosen a good rule
for our CA) contain patterns that look all the world like SASs, moving
through their world, reacting to their environment, having a sense of
passing time, etc.

This simple thought experiment generates some fascinating philosophical
questions. Are those SASs actually conscious? If so, at what point did they
become conscious? Was it at the moment that our testing algorithm decided
that that particular 4D block followed our specified CA rule? Or is it
later, when we "animate" portions of the 4D block so that we can watch
events unfold in "realtime"? These are not rhetorical questions - I'd
really like to hear your answers, because it might help me get a handle on
your position. (I'd like to hear other people's answers as well, because I
think it's a fascinating problem.)

Anyway, the point that I'm really trying to make is that, while these
thought experiments have a lot of bearing on the question of mathematical
existence vs. physical existence, they have nothing at all to do with
quantum physics or Heisenberg uncertainty. The fact it seems so to you
makes me think that we're not even talking about the same problem.

-- Kory
Received on Tue Jan 27 2004 - 08:48:54 PST