On 02 Mar 2014, at 08:09, Stathis Papaioannou wrote:
On 1 March 2014 01:40, Bruno Marchal <[email protected]> wrote:
>> 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.
>
>
>> 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 think functionalism is true, but it's not obviously true, at least
to most people. It could be that the observable behaviour of the
brain is reproduced perfectly but the resulting creature has no
consciousness or a different conscious.
What if someone says that the function of the brain is to provide
consciousness. Is that functionalism?
What if someone says that the function of the brain is to link a
"divine" soul to a person through a body?
What is a function?
That would be the case if consciousness were substrate-dependent.
But you can put the substrate in the function. A brain would have the
function to associate to that substrate the experience. How could I
say no to the doctor who guaranties that all the function of the brain
are preserved.
The term function, like set, is too general, to much powerful.
It could also be that the behaviour cannot be reproduced by a
computer because the substitution level requires non-computable
physics (true randomness, real numbers, non-computable functions),
but it could be reproduced by a non-computational device. So there
are these possibilities with brain replacement:
(a) the behaviour is not reproduced and neither is the consciousness;
= ~ BEH-MEC
(b) The behaviour is reproduced but the consciousness is not
reproduced;
~ comp.
(c) The behaviour is reproduced and so is the consciousness;
= comp, unless it is the consciousness is the one by an impostor.
(d) The behaviour is not reproduced but the consciousness is
= "bad" substitution.
>> 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.
Yes, a dualist, for example, could consistently deny fuctionalism,
Not sure. It depends on how you define function.
but someone who believes that consciousness is due to the brain
could not.
Most dualist believes that consciousness is due to the brain. They
will usually deny that the functional relation can be obtained with
this or that type of functions, but to throw out all functions, makes
their theory spurious. There will lost both interactionism and
epiphenomenalism.
Maybe you are on some idea, but you should take another word, as in
philosophy of mind, functionalism is used for Putnam's
computationalism. I do see vaguely what you mean, but it is still hard
to define this precisely. It corresponds to the infinities of
weakening comp, by adding oracle, or things like that.
My old definition of comp was En (functionalism is true at level n),
making functionalism à-la Putnam a restricted from of comp. Your
terming is non standard and can lead to confusion, imo. You might use
"mechanism" instead, with the idea that not all machines are digital
indeed.
Bruno
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Stathis Papaioannou
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