On 25 Apr 2017, at 15:26, Stathis Papaioannou wrote:
On Sun, 23 Apr 2017 at 5:58 am, John Clark <[email protected]>
wrote:
On Sat, Apr 22, 2017 Stathis Papaioannou <[email protected]> wrote:
>> Suppose just for the sake of argument that non-
physical computations did not exist, how would our physical world be
different? There would be no difference. Therefore either non-
physical computations do not exist or they do but are utterly
unimportant, rather like the luminiferous aether.
> This is equivalent to supposing that mathematical Platonism
is false.
Not exactly. Einstein didn't prove the luminiferous
aether didn't exist in the Platonic sense, he just proved it was
unimportant. I suppose you could say in the vague way that Greek
philosophers love that correct mathematical calculations exist
independently of matter, but the trouble is incorrect mathematical
calculations exist too, and the only way to differentiate the
correct from the incorrect is by using matter that obeys the laws of
physics. And separating the stuff we want from the stuff we don't is
important, that's why we say Michelangelo's huge statue of David is
500 years old and not far older even though in the platonic sense
David was inside a gigantic block of Carrara marble for 100
million years and all Michelangelo did was unpack it, he just
removed the parts of the block that weren't David.
But if the statue were conscious and it's consciousness not
dependent on interaction with the outside world, it would still be
conscious inside the marble block.
Any physical object could be viewed as implementing a computation as
anything could be mapped onto of a Turing machine, but the "work" of
the computation would then be not in the physical object but in the
mapping, a Platonic object. The problem with this is that such an
implementation cannot interact with its environment, so you cannot,
as you say to Bruno, use it to make money hiring out your Platonic
computer. But what if we consider conscious computation that does
not interact with the environment of its implementation? Like the
statue in the block of marble, it would still be conscious even if
no-one outside could appreciate it or make money out of it.
The idea that computationalism implies that consciousness would
occur independently of physical activity has been used as an
argument against computationalism, on the grounds that it is self-
evidently absurd. Hilary Putnam, originator of functionalism (of
which computationalism is a subset),
I guess you meant the contrary. Hillary Putnam's functionalism is a
subset of computationalism. Putnam used the Turing machine, making it
computationalist, but is vague on the notion of substitution level,
which he took at the level of brain or body. In my 1994 long text, I
defined computationalism explicitly like En(Fonct n), i.e. it exist a
level of substitution n such that digital functionalism is correct at
level n. Fodor, a student of Putnam, extracted the representaional
theory of mind from Putnam's fonctionnalism, which confirms the use of
digital representation assumed to exist in the brain. But
computationalism is neutral on this, or, at most very weakly
representational. It admits that we might survive only a a level so
low that the notion of representation becomes spurious, like if we
survive only with the copy of the entire Milky Way done at the level
of superstring theory. No reasonable cognitive scientist would put
this in Putnam-Fodor representational type of theory of mind.
Now, functionalism, without Turing machine, is a superset of
computationalism. It can invoke notions like analog function on the
real.
later realised this implication and changed his mind. John Searle
and Tim Maudlin came to a similar conclusion.
But an alternative is, as Bruno suggests, to keep computationalism
and accept that the apparent physical world is secondary, not
primary. The physical computers sold by Dell or IBM, along with
everything else, are made in a virtual reality running on a Platonic
computer. While this may at first glance seem absurd, there is no
reason I can think of why it cannot be true. And it has advantages
in addition to preserving computationalism, such as eliminating the
need to explain why there should be a physical universe at all.
OK.
Bruno
Bruno likes to talk about Robinson Arithmetic but as far as I can
tell even Raphael Robinson never claimed he had proven the
existence of non-physical calculations, instead he showed that if
you do certain activities in a certain sequence then you can produce
correct mathematical calculations without producing any incorrect
mathematical calculations. But without matter that obeys the laws of
physics you can't "do" anything, that's why a book by itself can't
perform a calculation or "do" anything else either, not even a book
on Robinson Arithmetic.
John K Clark
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