On 17 Apr 2015, at 18:55, Stathis Papaioannou wrote:
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.
That is certainly needed for the first six steps, but at step seven,
we can relax comp up to the quantum level, and below. The UD emulates
all programs, including all quantum computer, because the quantum
computer are Turing emulable, sure with an exponential slow down, but
the UD does not care, as, in arithmetic, it has "all the time".
In fact, as I said to Bruce, at step seven, we can understand why
"matter" cannot be duplicated exactly, because "matter", in term of
computation, is the result of the FPI on the whole work of the UD.
Below your substitution level, you cannot entangle yourself with token
facts, as they are not relevant for your most probable computational
history, so you multiply yourself more and more on the details.
Eventually, to get all the decimal exact, you need to run the entire
dovetailing, which is impossible.
Bruno
--
Stathis Papaioannou
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