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DESCARTES, RENÉ DU PERRON (b. La Haye,
Touraine, France, 31 March 1596; d. Stockholm,
Sweden, 11 February 1650), natural philosophy, scientific
method, mathematics, optics, mechanics, physiology.
Fontenelle, in the eloquent contrast made in his
Éloge de Newton, described Descartes as the man
who “tried in one bold leap to put himself at the
source of everything, to make himself master of the
first principles by means of certain clear and fundamental
ideas, so that he could then simply descend to
the phenomena of nature as to necessary consequences
of these principles.” This famous characterization
of Descartes as the theoretician who “set
out from what he knew clearly, in order to find the
cause of what he saw,” as against Newton the experimenter,
who “set out from what he saw, in order to
find the cause,” has tended to dominate interpretations
of both these men who “saw the need to
carry geometry into physics.”1
Descartes was born into the noblesse de robe, whose
members contributed notably to intellectual life in
seventeenth-century France. His father was conseiller
to the Parlement of Brittany; from his mother he
received the name du Perron and financial independence
from property in Poitou. From the Jesuits
of La Flèche he received a modern education in
mathematics and physics—including Galileo's telescopic
discoveries—as well as in philosophy and the
classics, and there began the twin domination of
imagination and geometry over his precocious mind.
He described in an early work, the Olympica, how he
found “in the writings of the poets weightier thoughts
than in those of the philosophers. The reason is that
the poets wrote through enthusiasm and the power
of imagination.” The seeds of knowledge in us, “as
in a flint,” were brought to light by philosophers
“through reason; struck out through imagination by
poets they shine forth more brightly.”2 Then, after
graduating in law from the University of Poitiers, as
a gentleman volunteer in the army of Prince Maurice
of Nassau in 1618 he met Isaac Beeckman at Breda.
Beeckman aroused him to self-discovery as a scientific
thinker and mathematician and introduced him to a
range of problems, especially in mechanics and
acoustics, the subject of his first work, the Compendium
musicae of 1618; published posthumously in
1650. On 26 March 1619 he reported to Beeckman
his first glimpse of “an entirely new science,”3
which
was to become his analytical geometry.
Later in the year, on 10 November, then in the duke
of Bavaria's army on the Danube, he had the experience
in the famous poêle (lit. “stove,”
“well-heated
room”), claimed to have given direction to the rest
of his life. He described in the Discours de la méthode
how, in a day of solitary thought, he reached two
radical conclusions: first, that if he were to discover
true knowledge he must carry out the whole program
himself, just as a perfect work of art or architecture
was always the work of one master hand; second, that
he must begin by methodically doubting everything
taught in current philosophy and look for self-evident,
certain principles from which to reconstruct all the
sciences. That night, according to his seventeenth-century
biographer Adrien Baillet, these resolutions
were reinforced by three consecutive dreams. He
found himself, first, in a street swept by a fierce wind,
unable to stand, as his companions were doing, because
of a weakness in his right leg; second, awakened
by a clap of thunder in a room full of sparks; and
third, with a dictionary, then a book in which he read
Quid vitae sectabor iter? (“What way of life shall I
follow?”), then verses presented by an unknown man
beginning Est et non; he recognized the Latin as the
opening lines of two poems by Ausonius. Before he
finally awoke he had interpreted the first dream as
a warning against past errors, the second as the
descent of the spirit of truth, and the third as the
opening to him of the path to true knowledge. However
this incident may have been elaborated in the
telling, it symbolizes both the strength and the hazards
of Descartes's unshakable confidence and resolve to
work alone. But he did not make his vision his life's
mission for another nine years, during which (either
before or after his tour of Italy from 1623 to 1625)
he met Mersenne, who was to become his lifelong
correspondent, and took part in scientific meetings in
Paris. The next decisive incident, according to Baillet,
was a public encounter in 1628 in which he demolished
the unfortunate Chandoux by using his method
to distinguish sharply between true scientific knowledge
and mere probability. Among those present was