Re: UDA revisited

From: Russell Standish <>
Date: Mon, 20 Nov 2006 00:03:15 +1100

On Sun, Nov 19, 2006 at 01:33:13PM +1100, Colin Geoffrey Hales wrote:
> <snip>
> > Since it makes no difference in any observable respect whether we are
> living in a computer simulation running on a bare substrate, as one that
> is incidently computated as part of a universal dovetailer, or an
> infinite chain of dovetailers, we really can make use of Laplace's ripost
> to Napoleon "Sire, I have no need of that hypothesis" with
> respect to a concrete computer running our world.
> <snip>
> Sorry Russel, I disagree with this claim.
> To say that the universe is computation does not imply any old substitute
> computed abstraction will be identical in all respects.
> In particular there is a blizzard of virtual theorems made available
> because of the intrinsic parallelism of 'reality as computation'. These
> are NOT explictly computed. Abstract it and all the virtual
> theorems/computations are gone.
> To see a computational equivalent check out ANY cellular automaton. There
> is a perfectly computational but uncomputed relationship between any cell
> and _all_ other cells (NOT just the local cells explicit to the rule set
> used). Yet the only thing that was actually computed was the cell contents
> using local cells incorporated in the cell rules. The universe is
> equivalent. It is computation and can be regarded/treated as a massively
> parallel CA. All the virtual theorems (computations) actually exist.
> So: Computationalism is the statement that "I am a computation".
> .... is correct in that the universe is computation, but incorrect in that
> an abstraction on a substrate will replicate everything - is cannot/does
> not replicate the virtual theorems. SO.....I have shown you a _physical_
> but virtual computation that is NOT replicated by the UDA abstraction.
> This makes your original assertion incorrect.

I have never heard of your "virtual theorems" before, but assuming
they're analogous to the implied computations that occur in your CA
example, the difference would be the other way around. A UD will
actually compute all these implied computations, whereas they are only
virtual with respect to a direct computation.

So you could make a statement that the difference between living in a
direct computation and living in a UD is that in the direct
computation there isn't this "blizzard of virtual theorems". But
there is another difference, as pointed out by Bruno - in a UD, first
person histories are non-deterministic. The point has been well argued
in this list as to whether this is significant or not (I for one happen to
think it is significant).

Finally, there is a problem that UDs are far simpler programs than the
one implementing our universe, so assuming they exist (which they do
by virtue of computationalism), we are far more likely to find
ourselves in a UD than in a simple direct computation.

> The story is bigger than this in that I hold the virtual theorems to be
> the substrate for subjective experience....but my claims in this regard do

Interesting claim. And if what I stated above holds, it meshes quite
nicely with the view that counterfactuals are essential for conscious

A/Prof Russell Standish                  Phone 0425 253119 (mobile)
UNSW SYDNEY 2052         
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Received on Sun Nov 19 2006 - 18:17:32 PST

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