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Re: More on Churchland
ray scupin (scupin@LINDENWOOD.EDU)
Tue, 19 Sep 1995 16:34:42 -0500
On Tue, 19 Sep 1995, John McCreery wrote:
> In my last message, I was talking about Patricia Churchland's
> _Neurophilosophy_ and had just noted that her animus is
> directed against the idea that the "software" studied by
> philosophers and cognitive psychologists can be isolated from the
> "hardware" of neurophysiology. I then found myself late for
> work and ended the message too abruptly to be clear about what
> I was saying. Here I resume that thread.
>
> Speaking historically, Churchland notes that the the basic division
> of software and hardware reflects a categorical split as old as
> Western philosophy. It starts, perhaps, with Plato's dividing the
> world of Ideas from the world of Matter and returns full force to
> the modern world in Descartes' division between Mind and Body.
> It also reflects, of course, the Christian conception of the soul
> which survives the mortal body and will be reborn in a new
> body at the Resurrection.
>
> If, however, Churchland were merely rehearsing familiar
> materialist arguments she would not be as interesting as she is.
> She observes that the software imagined by cognitive
> psychologists and philosophers characteristically takes the form
> of sentential logic, i.e., a logic in which sentences are related
> sequentially by formal rules that govern valid sequences. The
> mind is thus conceived as operating like a program written to
> run on a single CPU that can process only one instruction at a
> time. The central difficulty of programs written in this way
> which attempt to mimic the operations of human thinking is
> combinatorial blowup. They require literally millions and billions
> of steps to calculate the contingencies involved in apparently
> simple acts, e.g., recognizing a familiar face. (More complex
> calculations would require more steps than the number of
> electrons in the visible universe!) But, as Churchland observes,
> and Helmholtz demonstrated, nerve impulses travel much slower
> than the speed of sound. If, while silicon switches operate at
> nanosecond speeds, neurons fire in milliseconds, so that even the
> simplest reflexes require between 100 and 200 milliseconds,
> how, then, can the brain outperform the computer? The answer
> must be some form of massively parallel processing with
> cascading operations whose form is not at all that of sequential,
> sentential logic. The alternative may, for example, be something
> like matrix operations on tensors which--and here is where it
> gets interesting--do a good job of modeling prototype effects,
> where inputs can depart in varying degrees from a prototypical
> image. Voila! We are suddenly talking formal systems that give
> us a handle on things like "family resemblances" a la
> Wittgenstein, "polythetic classifications," "metaphors," etc. We
> may be looking at the first radically new empirical view of how
> the mind operates since Aristotle wrote the _Organon_ (a view
> supported on other grounds by anthropologically minded
> linguists like George Lakoff in _Women, Fire and Dangerous
> Things_). Of course, all this is speculative. But it's nicely grounded
> speculation and a powerful stimulus to fresh thought.
In my view Churchland's connectionist views and the model of parallel
processing computers as more likely than sequential logic models
suggested by the artificial intelligence models to help understand
neuronal processing is valid. However, we may need to have both types of
models---the connectionist model for understanding basic types of
perceptions and stimulations, and the sequential logic models for
understanding higher order logical-linguistic-symbolic processes. This
is the direction noted by Bloch in his essay "Anthropology and Cognitive
Science." He refers to the work of the philosopher Bechtel, who has
published in _Language and Mind_. Andy Clark is another philosopher who
synthesizes the connectionist models of the Churchlands with that of the
logical-sequential model. Bechtel and Churchland are working in the PNP
program (Philosophy-Neurology-Psychology) at Washington University in St.
Louis.
Yours,
Ray Scupin
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