Stathis Papaioannou wrote:
On Friday, April 17, 2015, Bruce Kellett <bhkell...@optusnet.com.au <mailto:bhkell...@optusnet.com.au>> wrote:Stathis Papaioannou wrote:Physicalism reduces to computationalism if the physics in the brain is Turing emulable, and then if you follow Bruno's reasoning in the UDA computationalism leads to elimination of a primary physical world. But physics itself is not Turing emulable. The no-cloning theorem of quantum physics precludes it.Do you mean because you can't exactly copy a given physical state? That doesn't necessarily mean the physical world as a whole cannot be emulated. And if it turns out that physics is continuous rather than than discrete you could still come arbitrarily close with digital models of the brain; if that was not good enough you would be saying that the brain is a machine with components of zero engineering tolerance.
An exact copy of an unknown quantum state is not possible. It most certainly does mean that the physical world as a whole cannot be emulated. Quantum mechanics is based on the incommensurability of pairs of conjugate variables. Because you cannot measure both the position and momentum of a quantum state to arbitrary precision simultaneously, we find that there are two complementary descriptions of the physical system -- the description in position space and the description in momentum space. These are related by Fourier transforms. Any complete description of the physical world must take this into account.
If a quantum state could be duplicated, then you could measure position exactly on one copy and momentum on the other. Exact values for these two variables simultaneously contradicts the basis of quantum mechanics. And there are very good arguments for the view that the world is at base quantum: the classical picture only emerges from the quantum at some coarse-grained level of description. You cannot describe everything that happens in the physical world from this classical, coarse-grained perspective.
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