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

Scholasticism, as a system of education, taught its students the wisdom of the
ancients. The scientific revolution that took flight in the sixteenth and seventeenth
centuries arose in reaction to this pedagogical tradition. The discoveries of such
luminaries as Newton and Leibniz were only possible when the ancient wisdom was
directly questioned and challenged.
The seventeenth-century philosophy of René Descartes (1996, 2006) provided
another example of fundamental insights that arose from a reaction against scholasticism.
Descartes’ goal was to establish a set of incontestable truths from which a
rigorous philosophy could be constructed, much as mathematicians used methods
of deduction to derive complete geometries from a set of foundational axioms. “The
only order which I could follow was that normally employed by geometers, namely
to set out all the premises on which a desired proposition depends, before drawing
any conclusions about it” (Descartes, 1996, p. 9).
Descartes began his search for truth by applying his own, new method of
inquiry. This method employed extreme skepticism: any idea that could possibly be
doubted was excluded, including the teachings of the ancients as endorsed by scholasticism.
Descartes, more radically, also questioned ideas supplied by the senses
because “from time to time I have found that the senses deceive, and it is prudent
never to trust completely those who have deceived us even once” (Descartes, 1996,
p. 12). Clearly this approach brought a vast number of concepts into question, and
removed them as possible foundations of knowledge.
What ideas were removed? All notions of the external world could be false,
because knowledge of them is provided by unreliable senses. Also brought into
question is the existence of one’s physical body, for the same reason. “I shall consider
myself as not having hands or eyes, or flesh, or blood or senses, but as falsely
believing that I have all these things” (Descartes, 1996, p. 15).
Descartes initially thought that basic, self-evident truths from mathematics
could be spared, facts such as 2 + 3 = 5. But he then realized that these facts too
could be reasonably doubted.
How do I know that God has not brought it about that I too go wrong every time I
add two and three or count the sides of a square, or in some even simpler matter, if
that is imaginable? (Descartes, 1996, p. 14)
With the exclusion of the external world, the body, and formal claims from mathematics,
what was left for Descartes to believe in? He realized that in order to doubt,
or even to be deceived by a malicious god, he must exist as a thinking thing. “I must
finally conclude that this proposition, I am, I exist, is necessarily true whenever it
is put forward by me or conceived in my mind” (Descartes, 1996, p. 17). And what
is a thinking thing? “A thing that doubts, understands, affirms, denies, is willing, is
unwilling, and also imagines and has sensory perceptions” (p. 19).
Elements of Classical Cognitive Science 57