On 26 Feb 2014, at 13:08, Stathis Papaioannou wrote:
On 26 February 2014 04:51, Bruno Marchal <[email protected]> wrote:
The point of this is that if the brain is responsible for
consciousness it is absurd to suppose that the brain's behaviour
could
be replaced with a functional analogue while leaving out any
associated qualia. This constitutes a proof of functionalism, and of
its subset computationalism if it is further established that
physics
is computable.
?
On the contrary if computationalism is correct the physics cannot be
entirely computable, some observable cannot be computed (but it
might be no
more that the "frequency-operator", like in Graham Preskill. But
still, we
must explain why physics seems computable, despite it result of FMP
on non
computable domains).
If you start with the assumption that the physics relevant to brain
function is not computable then computationalism is false: it would be
impossible to make a machine that behaves like a human, either zombie
or conscious.
I agree with you, the physics *relevant* to brain function has to be
computable, for comp to be true. But the point is that below the
substitution level, the physical details are not relevant. Then by the
FPI, they must be undetermined, and this on an infinite non computable
domain, and so, our "computable brain" must rely on a non computable
physics, or a non necessarily computable physics, with some non
computable aspect. This is what comp predicts, and of course this is
confirmed by QM. Again, eventually, QM might to much computable for
comp to be true. That is what remain to be seen.
Also,you are not using "functionalism" in its standard sense, which
is
Putnam names for comp (at a non specified level assumed to be close
to
neurons).
What do you mean by function? If you take all functions (like in set
theory), then it seems to me that functionalism is trivial, and the
relation
between consciousness and a process, even natural, become ambiguous.
But if you take all functions computable in some topos or category,
of
computability on a ring, or that type of structure, then you
*might* get
genuine generalization of comp.
What I mean by functionalism is that the way the brain processes
information, its I/O behaviour, is what generates mind. This implies
multiple realisability of mental states, insofar as the same
information processing could be done by another machine. If the
machine is a digital computer then functionalism reduces to
computationalism. If the brain utilises non-computable physics then
you won't be able to reproduce its function (and the mind thus
generated) with a digital computer, so computationalism is false.
However, that does not necessarily mean that functionalism is false,
since you may be able to implement the appropriate brain function
through some other means. For example, if it turns out that a digital
implementation of the brain fails because real numbers and not
approximations are necessary, it may still be possible to implement a
brain using analogue devices.
OK, but that functionalism seems to me trivially true. How could such
functionalism be refuted, if you can invoke arbitrary functions?
(Also, "functionalism" is used for a stringer (less general) version
of computationalism, by Putnam, so this use of functionalism is non
standard and can be confusing.
Last remark, I am not sure that the notion of information processing
can make sense in a non digital framework. In both quantum and
classical information theory, information is digital (words like bits
and qubits come from there).
I don't think we have to settle for Bruno's modest
assertion that comp is a matter of faith.
It has to be, from a theoretical point of view. Assuming you are
correct
when betting on comp, you cannot prove, even to yourself (but your
1p does
not need that!) that you did survive a teleportation.
Of course I take "proof" in a rather strong literal sense. Non comp
might be
consistent with comp, like "PA is inconsistent" is consistent with
PA.
What can be proved is that if consciousness is due to the brain then
replicating brain function in some other substrate will also replicate
its consciousness.
OK. What I meant is that we cannot prove that consciousness is due to
the brain.
Bruno
--
Stathis Papaioannou
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