On 27 Jan 2005 Tianran Chen wrote:
These considerations are valid if we are discussing how one would actually go about simulating a world or mind in OUR universe, so that we could interact with it, or at least eavesdrop. But Egan's point in the novel, as I understood it, was that the requisite computations would occur (and occur necessarily) in noise, perfectly hidden from us. Trying to "find" the computations in the noise would be at least as difficult as building a conventional computer and programming it from scratch, so in this sense, the claim that that there is this hidden information there at all is meaningless. However, if we allow that a computation can give rise to consciousness, why should that consciousness be contingent on our ("we" being conscious beings at the computer's level) ability to observe and recognise it as such?
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.
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).
For example, if I am running an AI program on my computer and a particular bitstring is associated with the simulated being noting, "I think, therefore I am", then should not the same bitstring arising by chance in the course of, say, a spreadsheet calculation give rise to the same moment of consciousness - regardless of whether the spreadsheet user or anyone other than the simulated being himself is or can be aware of this?
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