374 RENÉDESCARTES
knowledge must be based on certainty and that he had a system that provided that
basis. Encouraged by others to develop his system, he retired to Holland, where
he found a greater degree of intellectual freedom and spent the next twenty years
writing and publishing his ideas. His major philosophical works include Rules for
the Direction of the Mind(written 1628, but not published until 1701),Discourse
on Method(published in 1637 as a preface to the essays Geometry,Dioptric, and
Meteors), and Meditations on First Philosophy(1641). Descartes also published
seven sets of Objections to the Meditationsof thinkers such as Hobbes, Arnauld,
and Gassendi, accompanied by his Reply to Objections.In addition to his work in
philosophy, Descartes made major contributions to the fields of optics, anatomy,
physiology, and mathematics (especially analytic geometry in which “Cartesian
coordinates” are still used).
Descartes chose to write his works in French as well as Latin in order to reach
beyond the academics to a wider audience. His writings did, indeed, reach learned
people throughout Europe and that fact, unfortunately, led indirectly to his death.
In 1649, Queen Christina of Sweden invited Descartes to join a circle of leading
thinkers to instruct her in philosophy. Although he initially resisted the invitation,
he finally felt compelled to accept. Upon arriving in Sweden, Descartes discovered
that Queen Christina had time to see him only at five each morning. Descartes had
been used to lying in bed until late in the morning, reflecting and philosophizing.
Within a year, the rigorous new schedule, together with Sweden’s harsh weather,
led to his death.
Descartes began his philosophy by sweeping away all the “errors of the past.”
Whereas Bacon turned to empirical observation to escape the “tyranny” of the
past, Descartes turned to mathematics, specifically geometry. He began by estab-
lishing twenty-one Rules for the Direction of the Mind. He would begin by finding
knowledge that he could “clearly and evidently intuit, or deduce with certainty.”
Then he would build from this knowledge deductively, one step at a time. This pro-
cedure would parallel the geometrical method of moving with deductive certainty
from postulates to axioms. His Meditations on First Philosophy,reprinted here
(complete) in the outstanding John Cottingham translation, chronicles this process.
The key was to find the knowledge that he could “clearly and evidently intuit”
that could serve as his starting point. Although uncertainty and doubt were the
enemies, Descartes hit upon the idea of using doubt as a tool or a weapon.
Instead of fighting doubt, he would use it to find certainty. He would use doubt
as an acid to pour over every “truth” to see if there was anything that would not
be dissolved, any “truth” that could not be doubted. Some of his doubts may
seem extreme (such as that the earth may not exist or that I may be dreaming all
this), but in order to find 100-percent certainty he had to find a starting point
with zero-percent doubt.
After subjecting all his knowledge to the acid of doubt, he concluded that
there was one thing he could not doubt: that he was doubting. The one fact the
acid of doubt could not dissolve was doubt itself. This meant there had to be an
“I” who was doing the doubting. Even if he were deceived about everything else,
he had to exist in order to be deceived. This led Descartes to his famous state-
ment,Cogito ergo sum,meaning “I think, therefore I am” (although these exact
