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. 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. 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*. 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. 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. David -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. Visit this group at http://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout.
