CHAPTER XI
Brains and Thoughts
New Perspectives on Thought
IT WAS 0 N L Y with the advent of computers that people actually tried to
create "thinking" machines, and witnessed bizarre variations on the theme
of thought. Programs were devised whose "thinking" was to human think-
ing as a slinky flipping end over end down a staircase is to human locomo-
tion. All of a sudden the idiosyncracies, the weaknesses and powers, the
vagaries and vicissitudes of human thought were hinted at by the new-
found ability to experiment with alien, yet hand-tailored forms of
thought-or approximations of thought. As a result, we have acquired, in
the last twenty years or so, a new kind of perspective on what thought is,
and what it is not. Meanwhile, brain researchers have found out much
about the small-scale and large-scale hardware of the brain. This approach
has not yet been able to shed much light on how the brain manipulates
concepts, but it gives us some ideas about the biological mechanisms on
which thought manipulation rests.
In the coming two Chapters, then, we will try to unite some insights
gleaned from attempts at computer intelligence with some of the facts
learned from ingenious experiments on living animal brains, as well as with
results from research on human thought processes done by cognitive
psychologists. The stage has been set by the Prelude, Ant Fugue; now we
develop the ideas more deeply.
Intensionality and ExtensionalityThought must depend on representing reality in the hardware of the brain. In
the preceding Chapters, we have developed formal systems which repre-
sent domains of mathematical reality in their symbolisms. To what extent is
it reasonable to use such formal systems as models for how the brain might
manipulate ideas?
We saw, in the pq-system and then in other more complicated systems,
how meaning, in a limited sense of the term, arose as a result of an
isomorphism which maps typographical symbols onto numbers, opera-
tions, and relations; and strings of typographical symbols onto statements.
Now in the brain we don't have typographical symbols, but we have some-
thing even better: active elements which can store information and trans-
mit it and receive it from other active elements. Thus we have active
symbols, rather than passive typographical symbols. In the brain, the rulesBrains and Thoughts 337