On 8/22/2014 6:46 PM, 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.
What we observe, aside from observing our own thoughts and maybe even then, is always
theory laden. Partly we see the world through a theory of objects that evolution has
provided us, sort of naive physics, but a theory nonetheless as optical illusions demonstrate.
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.
Right, because it usually (modulo a dropped bit or so) does.
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.
I think you are too hung up on ontology. You denigrate everything that's not in terms of
the ur-stuff of (some unknown) true ontology as metaphor or fiction. Why not accept that
knowledge, including knowledge of ontology, is always provisional and uncertain and it's
best to think of it as a model summarizing our best idea - but not necessarily the one
TRUE idea.
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".
Suppose the "physical reality" isn't primitive. So what? Molecules aren't primitive,
even atoms aren't primitive. But we can still describe life in terms of certain processes
at the molecular level.
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*. 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.
I'd say that pretty much the standard physical account of consciousness.
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.
It adds a great deal of intelligiblity, just as explaining how organic molecules manage to
perform metabolism, growth, and reproduction and to evolve as part of living entities.
There's lots of stuff we can't understand at the level of 10^32 atoms but which we easily
grasp at the level of a table and chair. That doesn't mean we've invoked some magic.
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.
ISTM that's like saying I'm not going to consider CTM unless it can saved from being
merely useful and/or approximate and shown to be absolute.
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.
I don't think it's any harder than the problem that Bruno created in the first place by
taking computation as basic. That means that mind AND matter have to be explained as
computation. It may make the mind part a little easier, but I think it leaves the matter
part pretty hard.
Brent
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