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shminux comments on Debugging the Quantum Physics Sequence - Less Wrong Discussion
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Personally, I am against linking MWI or even QM to rationality in any way, as the connection seems to be quite arbitrary.
Consider a matrix-like world, where the Universe is simulated on a classical computer (classical computers can do everything quantum computers can do, if slower). Would you deny that simulated humans can think and act rationally, only because the simulation does not include quantum mechanics? If not, would sim-EY not be able to write the Simquences (less the QM Sequence) which are identical (modulo QM) to the ones here?
It seems to me like the universe could be simulated on a quantum computer without quantum mechanics in the simulation, or even in a classical computer with quantum mechanics in the simulation (though it'd take a lot longer of course). The information processing itself is the important part, not the means of processing. This doesn't detract from your argument, which I agree with, I just wanted to point that out.
Right, I just wanted to underscore that no QM is required at any point (the point I mentioned before, but it never got any attention from EY).
You make a compelling case that the reference to QM in the sequences is at least as arbitrary as the fundamental physics of our universe. I'm not sure that this is quite as compelling and incisive a revelation as you believe it to be, especially to those who take Occam's Razor as seriously as Eliezer advocates. I'd actually say that this weakens your claim and that it would be better to argue, as Tim does, that the points Eliezer is trying to express don't come across nearly as well as they could.
The first question - there's no reason in the QM sequence to suspect that simulated humans would not be able to think or act rationally. The phenomenon of rationality is well-screened from the implementation layer of the universe.
Sim-EY would be correct about that implementation layer of his universe that screens off all the lower levels. That is, his statements about the universe are true of the simulation, which, as far as he can tell, is all there is. His words have valid referents. And indeed, MWI would be correct in that domain.
That there is another implementation layer out there that isn't quantum... eh so? We're perfectly screened from it, so that's not what we're talking about.
My point exactly, QM (and hence the QM sequence) is not needed for rationality training.
You lost me with the last statement. MWI would be correct in what domain? The simulated one? Hardly, it's all classical and digital.
Total non-sequitur. The QM sequence was a case study. You don't need to understand QM to be rational, but to get where he was going, he needed to use something as an example.
The implementation of the simulation is classical digital. The simulated world is quantum, just like you said.
Ah, I see. Yes, it was a case study, just not a good one, given the controversy that distracts from the point. There are better examples.
I don't follow. What's the difference between the implementation and the simulated world?
In two simulations I ran once, the 'world', such as it was, was an FCC lattice each containing one of 2 kinds of atom, or vacuum, and the dynamics were ruled by a Monte Carlo algorithm.
It had two separate implementations, with very different MC engines. One was in Fortran77 and used the Metropolis algorithm; another was in C++ and used the Bortz-Kalos-Lebowitz MC algorithm. Both of these had effects on how dynamics progressed. They would be detectable by examination of the state of the world.
But which computer I chose to run it on would not. I put it on a Solaris machine; I put it on a Linux machine. the results were bitwise identical.
If you scale this notion up into the point that it could contain agents, and let these two swap save-files every so often, an agent inside could in principle tell which program was running at that time. But no agent could tell whether I'd changed from a Solaris box to a Linux box. So, the Metropolis vs BKL distinction is an element of their physics. The Solaris vs Linux distinction is not.
Accordingly, if we're in a simulation, and the simulation is pure quantum, but it's implemented in classical computers, it's not wrong to say MWI is correct. The referent is the implementation of quantum mechanics in those classical computers.
OK, I think I understand and mostly agree. Though I would make a weaker, interpretation-agnostic statement: "it's not wrong to say QM is correct". I don't think that it invalidates my original point, however, that it is likely possible to simulate human-like agents discussing rationality using, say, Newtonian physics, and such agents will have no need for QM.
Well, yes, but I don't see how that has anything to do with the QM sequence.
Again, my (and others') long-standing point has been that the QM sequence as a case study is not a good one. Given that the same rationality-related arguments can likely be made in a world without QM, and that the MWI discussion sparks too much controversy that detracts from the point (whatever it might be), it stands to reason that a different case study would serve this goal better (it can hardly be worse).
If the case-study pertained to banana custard stands, certainly rationality-related arguments would be devisable in a world without banana custard stands.
That aside - MWI being controversial is a fair point, which is why I didn't have anything to say about it in the post with the simulation analogy. I suppose I should have explicitly acknowledged that then, so you would not feel the need to raise it again. Sorry about that.