On 15/10/2015 12:07 pm, Jason Resch wrote:
On Wed, Oct 14, 2015 at 1:17 AM, Bruce Kellett
<[email protected] <mailto:[email protected]>> wrote:
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.
Well that explains it.
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.
What evidence have you seen that led you to this conclusion?
What evidence do you need to say that something does not exist? Absence
of evidence is, in this case, evidence of absence.
In mathematics you have descriptions of Turing machines and
descriptions of computations, but no live machines or computations.
There are both.
What evidence do you have for this assertion?
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.
But if it is independent of substrate, and if computations exist
platonically, then those platonic computations are equally capable of
instantiating consciousness.
You are confusing the meaning of 'substrate'. In the context, I meant an
explicitly physical substrate. Platonia is an idea, it is no more
'physically real' than is the idea of a unicorn, or of Hogwarts School.
Neither unicorns nor Hogwarts can instantiate consciousness. No more can
the idea of platonia.
If you want to demonstrate that the idea of platonia can sustain
consciousness of itself, then all you have to do is produce a conscious
being that does not have an accompanying physical substrate. Until you
do that, I think you should shut up about platonia.
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.
If you born in a universe with slightly different laws, you would say
this universe is only abstract and doesn't exist. I think you are just
biased by what is familiar to you.
No, I am talking about physical reality. Other universes with different
physical laws may or may not exist. If they do exist, they are, by
hypothesis, physical. So they can sustain Turing machines and
computations, maybe even consciousness if there are beings around
capable of building a physical Turing machine. But this is not so for
platonia. It is an idea, it is abstract, it does not exist in the
required physical sense, so it can do none of these things.
Bruce
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