On 07 Apr 2015, at 15:06, Stathis Papaioannou wrote:
On Tuesday, 7 April 2015, Bruno Marchal <marc...@ulb.ac.be> wrote:
On 06 Apr 2015, at 01:22, Stathis Papaioannou wrote:
I agree that if comp is true then consciousness cannot supervene on
physical activity, for the reasons in the MGA thread.
OK. Thanks for making this clear.
The only way out of this conclusion is to deny comp, which means to
deny CT.
I guess you are too quick. We can still deny comp, without denying
CT, for example by pretending that no copy will get the right
behavior, or even that the copy will be dead, and cannot be made
moving at all, perhaps because we believe in some magical God which
would not allow it, or whatever, or that all copies will be mentally
impaired, etc. It is only in the case where the copies behave the
same as the original, and claim they have no change in qualia, that
comp is follows from CT with the "no-partial-zombie" argument.
This does not imply CT is false, as the "magical soul", or the
"primitive matter", or the "infinitely low subst level (actually
infinite)", used to make someone saying "no" to the doctor, might
not add any new computability power, only that it would be needed to
remain alive and have the relevant behavior.
I guess you agree with this remark, as we were in the context of
copies having the right behavior and pretending to survive
perfectly. Obviously, a believer in CT, and not in comp, needs some
amount of magic, and perhaps we can derive comp from CT, if, like in
the MGA, we can show that indeed we need to add something magical.
I have to think more on this, as I might be quick again.
Hmm... A model could be given with having an infinite low
substitution level. When using a digital brain, people would
survive ... for some period of time, and then problems would add up,
due to truncation error, decimals incorrect, etc. The brain would be
a truly infinite machine, but without giving the person new
computability power. It seems to me right now.
What I intended by "CT" is the narrower physical version, which says
that all physics is computable.
OK. This clarifies your point. But the original CT has nothing to do
with physics. Also Deutsch's form of CT (everything physical can be
quantum Turing emulated (perhaps in polynomial time)) is not
equivalent with the original CT, and might be in conflict with it.
All physics might be computable, without the entire physical universe
being computable (which I thing is "figital physics".
With computationalism, a priori, the physical should not be
computable, but it has to be enough computable to disallow too much
white rabbits, something that QM seems to do remarkably well, but it
is an open problem with arithmetic. The reason is that the
indeterminacy on the computational histories might be too much big.
If that is true then at least the behaviour of a person should be
computable, though he may be a zombie if in fact consciousness has
nothing to do with physics but occurs in a separate spiritual realm.
What is incompatible is the following three beliefs:
(a) all physics is computable, and
(b) consciouness supervenes on brain processes, and
(c) consciousness is substrate-dependent and so will not be
reproduced even with a sufficiently fine-grained and perfectly well
behaved brain simulation.
OK.
I think that (a) and (b') are already incompatible:
(a) all physics is computable, and
(b') consciousness supervenes on *digital* brain processes.
But (a), (b) and (c) already make obligatory to derive physics from
the FPI on the whole UD*. The "winning" computation(s) are plausibly
the one with a linear symmetrical bottom, and which admit long (deep
in Bennett sense) computational histories. This makes us very rare in
the arithmetical reality, but also super-multiplied, and with natural
ways to entangle many universal machines in a many video-game type of
(observable, phenomelogical) reality.
I will surely come back on Church's thesis. It is a quite strong
thesis which implies incompleteness in one simple (double)
diagonalization. The original thesis asserts only that lambda-calculus
defines all intuitively computable function. It is provably equivalent
with the same thesis with lambda-calculus replaced by any know
(Turing) universal system. Does this implies comp? I doubt (given the
counter-example), but might be closer than I thought.
And if CT implies comp, or almost comp, then consciousness would be
close to being equivalent with the ability to get troubled by the
following sentence, which typically can neither be true nor false:
"Anyone currently reading the present sentence will never know that
this present sentence is true"
In arithmetic this sentences does *not* belongs to G* \ G, as it is
not even expressible (arithmetical truth is not expressible or
definable in arithmetic). There is no problem with the self-
reference, by using the Kleene's method sum up by if D('x') gives
T('x('x')'), then D('D') gives T('D'D'').
Approximations of truth can be made, and the corresponding sentences,
when they exist, can be true, or false, according to the
approximations, but then those approximations disconnects truth from
consciousness.
Hmm... apology because I am thinking aloud.
Bruno
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Stathis Papaioannou
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