On Friday, April 17, 2015, Bruce Kellett <bhkell...@optusnet.com.au> wrote:
> Stathis Papaioannou wrote: > >> On Friday, April 17, 2015, Bruce Kellett <bhkell...@optusnet.com.au >> <mailto:bhkell...@optusnet.com.au>> wrote: >> >> 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. >> >> You can't copy an arbitrary quantum state, but you could copy it by >> emulating a series of quantum states. >> > > ? > > 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. >> >> If you had an actual Turing machine and unlimited time, you could by >> brute force emulate everything. However, that is not the point. If you car >> needs a part replaced, you don't need to get a replacement exactly the same >> down to the quantum level. This is the case every machine, and there is no >> reason to believe biological machines are different: infinite precision >> parts would mean zero robustness. >> > > I think you miss the point. If you want to emulate a car or a biological > machine, then some classical level of exactness would suffice. But the > issue is the wider program that wants to see the physical world in all its > detail emerge from the digital computations of the dovetailer. If that is > your goal, then you need to emulate the finest details of quantum > mechanics. This latter is not possible on a Turing machine because of the > theorem forbidding the cloning of a quantum state. Quantum mechanics is, > after all, part of the physical world we observe. > Although you cannot clone an arbitrary quantum state, you might be able to simulate the set of all possible quantum states of which the unknown state is one. No cloning is needed. However, for Bruno's argument this level of simulation is not needed. What is needed is a level of simulation sufficient to reproduce consciousness, and this may be well above the quantum level. -- Stathis Papaioannou -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to everything-list+unsubscr...@googlegroups.com. To post to this group, send email to everything-list@googlegroups.com. Visit this group at http://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout.
