On 14/10/2015 4:45 pm, Jason Resch wrote:
Cochlear implants and artificial retinas give evidence toward multiple
realizability, and therefore, against mind-brain identity theory. They
show that it is functional equivalence, rather than
material/compositional equivalence that matters. Since computers can
realize any finite function, then assuming there are no necessary
infinities within the brain, computers can realize any functional
state the brain is able to realize. For physicalism to be correct, you
have to believe either that functional states are irrelevant to
consciousness, or that physics can instantiate functional states which
Turing machines cannot.
That is simply false.
Again it's not clear what you mean by computationalism. Bruce
can speak for himself, but I think he agrees that strong AI is
possible.
Strong AI implies consciousness is substrate independent. But I
thought Bruce argued against consciousness being derivable from
mathematical computations, which would mean consciousness is substrate
dependent: that it depends on physically implemented Turing machines.
I certainly argued that consciousness could not be sustained on platonic
computations in arithmetic. But that was because I do not accept that
such things exist. In mathematics you have descriptions of Turing
machines and descriptions of computations, but no live machines or
computations. Substrate independence simply means that you can replace
all or part of the human brain with computer-based equivalents. In other
words, strong AI. No need for platonia in order to say that
consciousness is independent of the substrate.
Why? Arithmetic is system of propositions. Whether it is real or
not has no effect on Church-Turing.
Then you should be equally happy to have your brain implemented by
"unreal computations" as "real computations" :-)
Computations in platonia are 'unreal' -- they do not exist, so cannot
implement anything.
and it's difficult to make sense of computationalism if you can no
longer define computation or computability. So if you accept
computationalism, you are implicitly accepting infinity and
arithmetical realism. Given this, the rest of Bruno's result is a
logical proof, which is either correct or has an error.
No, you missed the point that it is not a logical proof. It's an
argument from incredulity.
"A Turing Machine either reaches a halting state or runs forever"
"A Turing Machine can emulate any other Turing machine"
"A Turing Machine has an unlimited tape"
None of the above items are true for physical approximations of Turing
machines. If these basic principals of computer science are not true
for physical Turing machines, then what kind of Turing machines are
they true for? Is Computer Science founded on lies, or does it concern
itself with a recently-discovered mathematical object for which these
statements are true?
The definition is of an ideal Turing machine. No such ideal machine
exists. Mathematical objects are idealizations: they do not exist. Any
realization of a mathematical objects is necessarily less than ideal.
Bruce
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