Mind, Body, World- Foundations of Cognitive Science, 2013a

philosophical position called materialism. According to materialism, the mind is
caused by the brain. In spite of the fact that it has abandoned Cartesian dualism,
most of the core ideas of classical cognitive science are rooted in the ideas that
Descartes wrote about in the seventeenth century. Indeed, classical cognitive science
can be thought of as a synthesis between Cartesian philosophy and materialism.
In classical cognitive science, this synthesis is best expressed as follows: cognition
is the product of a physical symbol system (Newell, 1980). The physical symbol
system hypothesis is made plausible by the existence of working examples of such
devices: modern digital computers.
3.2 Mechanizing the Infinite
We have seen that the disembodied Cartesian mind is the thinking thing that mediates
the sensing of, and acting upon, the world. It does so by engaging in such activities
as doubting, understanding, affirming, denying, perceiving, imagining, and
willing. These activities were viewed by Descartes as being analogous to a geometer’s
use of rules to manipulate mathematical expressions. This leads us to ask,
in what medium is thought carried out? What formal rules does it employ? What
symbolic expressions does it manipulate?
Many other philosophers were sympathetic to the claim that mental activity
was some sort of symbol manipulation. Thomas Hobbes is claimed as one of the
philosophical fathers of classical cognitive science because of his writings on the
nature of the mind:
When a man Reasoneth, hee does nothing else but conceive a summe totall, from
Addition of parcels; or conceive a Remainder, from Substraction of one summe
from another.” Such operations were not confined to numbers: “These operations
are not incident to Numbers only, but to all manner of things that can be added
together, and taken one out of another. (Hobbes, 1967, p. 32)
Hobbes noted that geometricians applied such operations to lines and figures,
and that logicians applied these operations to words. Thus it is not surprising
that Hobbes described thought as mental discourse—thinking, for him, was
language-like.
Why were scholars taken by the idea that language was the medium in which
thought was conducted? First, they agreed that thought was exceptionally powerful,
in the sense that there were no limits to the creation of ideas. In other words, man in
principle was capable of an infinite variety of different thoughts. “Reason is a universal
instrument which can operate in all sorts of situations” (Descartes, 2006, p. 47).
Second, language was a medium in which thought could be expressed, because it
too was capable of infinite variety. Descartes expressed this as follows:
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