On 23 Aug 2014, at 03:46, David Nyman wrote:
I must confess that I've been reading the MGA revisited thread with
a certain sense of frustration (notwithstanding that Russell has
made a pretty good fist of clarifying some key points). My
frustration is that I have never been able to see why we need an
elaborate reductio like the MGA to dispose decisively of a
*computational* theory of mind on the basis of a primitive
materiality. The crux of the argument is whether the "computational"
part of the theory can be reduced without ambiguity to the action of
a physical device (e.g. a computer or a brain). If not, what we're
left with looks like a crypto-materialist theory in computationalist
disguise. In point of fact I agree with Stathis that multiple
realisability is already sufficient to establish this point. But let
me elaborate a little further. When we consider the matter, we don't
actually observed "computation" (in any rigorous mathematical sense)
in physical reality. What we observe in practice are physical
devices of various kinds (indeed, in principle, indefinitely many
kinds) that we accept FAPP as adequately instantiating particular
classes of computation within certain fairly stringent limits. To
put it another way, we are prepared to interpret the normal physical
behaviour of such devices *as if* it instantiated the mathematical
notion of computation.
I am with you on this. But this, I think, mean that you have the
platonist fiber, and well, the most usual "member of the jury" is
usually aristotelian. Even most today's mathematician.
For a platonist, from the start, the mathematical (notably
computational) is reality, and the physical can provide only
approximations, for some period of time.
We use our brain, as if he was instantiating the mathematical notion
of our soul, which in this case, it never does, the math is there
before, and our poor physical brains approximate the relations, and
probably blind us from the roots, as it could demotivate the
exploration hereby. (the theological trap)
Now, perhaps by developing the argument, you might convince the
aristotelians. The MGA is constructed to meet the aristotelian
nitpickers.
But at all times it is sufficient to assume that such behaviour, be
it of computers or brains, is constrained exclusively and
exhaustively by physical law. It's their net action, as physical
devices, that is at all times assumed to be essential, whatever
"computational" (or other) interpretation may be ascribed to them
externally. Unfortunately, these otherwise rather obvious facts tend
to be obscured in ordinary, and even in technical, discourse by the
free intermixing of software and hardware paradigms.
These considerations should make it clear that any description of
the normal behaviour of a physical device as computation can only be
in a sense that is, ultimately, metaphorical.
You might be quick or I might be tired :)
This extends to any software re-description of physical action, as
for example Brent's Mars Rover analogy, or Dennett's "third-person
absolutist" take on perception and cognition. On the assumption of a
"primitive physical reality", such descriptions can (and indeed
must) be understood as metaphorical and approximate, not literal and
"absolute". They are grounded in the assumption of their ultimate
reducibility, and approximate equivalence, to some kind of net
physical action. In this light, physical devices don't literally
"compute"; the most we need to say is that their physical behaviour
adequately *approximates* computation, under suitable interpretation
and within certain limits. Under such constraints, it would seem
that a so-called "computational" theory of mind could in fact amount
to nothing other than the claim that consciousness is a *state of
matter*.
I was OK, but this astonishes me ...
This particular state of matter, it would be claimed, must obtain
whenever physical action happens to be approximately re-describable
(at some arbitrary level) in terms of a certain class of
computation. But given that the theory is grounded, and is at all
times expressible, in terms of an explicitly physical, as distinct
from mathematical, ontology, it is hard to discern how such a
"computational" stipulation could contribute anything intelligible
to the claim.
... OK. I understand, and agree. Yes, the aristotelian use the
platonia and select consciousness with a piece of chimera, to
eliminate Platonia.
It is a generalization of Bohm's move in QM.
They believe Platonia is too big or to trivial. But this is ignoring
the math, or Plato.
ISTM that the foregoing considerations are sufficient, on their own
merits, to establish the necessity of the reversal at Step 8, if a
*computational* (as distinct from some sort of tacitly crypto-
material) theory of consciousness, is to be salvaged. If so, it is
indeed clear that the task becomes at least twice as hard as before,
as the observed correlations between matter and consciousness now
have to be justified on the basis of an ontology that is
(mathematically) adequate for a general and rigorous (as distinct
from local and approximate) emulation of computation.
Which motivates wonderfully for eventually asking the machine itself,
directly in Platonia, as comp provides the simplest, conceptually,
platonia, as, not much more than the sigma_1 arithmetical truth for
the ultimate outer-reality, and also its many organized,
mathematically structured, inexhaustible internal 1p views.
I have to go.
Best.
Bruno
PS As I said to Brent, I will be slowed down. I have visit tomorrow
and an heavy duty week after. Apology in advance for delayed answers.
Obviously we have to talk on MGA, and Russell's paper, but it is a
subtle matter (unavoidable pun). I still think there are confusion
between a computation, a description of a computation, an
implementation of a computation in platonia, an implementation in a
universal number, and an implementation in a physical reality (in the
comp sense of physics, and in the physicalist sense of physics, which
MGA should show not really working without adding non-Turing-emulable
magic).
David
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