Re: Belief Statements

From: Tianran Chen <>
Date: Wed, 26 Jan 2005 08:38:10 -0500

Hal Finney wrote:
> I had a problem with the demonstration in Permutation City. They claimed
> to chop up a simulated consciousness timewise, and then to run the pieces
> backwards: first the 10th second, then the 9th second, then the 8th,
> and so on. And of course the consciousness being simulated was not
> aware of the chopping.
> The problem is that you can't calculate the 10th second without
> calculating the 9th second first. That's a fundamental property of our
> laws of physics and I suspect of consciousness as we know it. This means
> that what they actually did was to initially calculate seconds 1, 2,
> 3... in order, then to re-run them in the order 10, 9, 8.... And of
> course the consciousness wasn't aware of the re-runs. But it's not clear
> that from this you can draw Egan's strong conclusions about "dust".
> It's possible that the initial, sequential run was necessary for the
> consciousness to exist.

I doubt this is the case.

First of all, I don't think you should call it "law" at all, since
such property is indeed derived purely from the interpretation we had
made so far about our world. Although these interpretations (QM,
Relativity, super string and etc.) are in favor now, they are
logically no more "valid" than Newton's physics at his time (or even
now). If we all this time dependency a "defect", then we (still) do
not know whether it is a defect of theories we favored, or a defect of
the world we are in now, or a defect of our reasoning ability, or even
a resultant defect induced from some other defect of our world.
Infinite (or at least very large) number of theory can be developed
based on finite number of observed facts, just like infinite numer of
curves can pass through finite number of common points. However, we
have principles like Occam's Razor to choose between them. How do we
know that some other theory may not suffer from this defect?

Second, even with the physics we use nowadays, there are still simple
problems that can be calculate NOT IN ORDER. For instance, the
displace of a single pendular at any time can be calculate regardless
of its history. Put into more formal way, there exist some turing
machine that can calculate in constant (regard to the time) steps.
More generally, dynamic systems and complex systems are the only thing
that has "history". However, many dynamic system can be translated
(however messly) into simple system of equations that can be solved in
constant time with some turing machine. Take gas for example, the
position of each molecule is no doubt a hard problem that only
expressed with dynamic system. However, if we are to talk about gas in
a higher level in terms of volume, pressure, and temperature, then
most problem can be expressed in simple systems that can be calculated
in constant time.

Finally, our physics world may be one of the limit that some problem
cannot be solved in constant time. This had been talked about quite
thoroughly in the discussion about super-turing computation. I don't
have much to add on to that.

Conclusion: A world can be simulated IN or OUT OF ORDER, depending on
the physics to be simulated, the world the simulator is in, and the
design of the simulator (which is related to the level of intellegence
of the designer in this particular case).
Received on Wed Jan 26 2005 - 09:29:41 PST

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