Rene Descartes

Rene Descartes was born March 31, 1596 in La Haye, Touraine. Descartes was the
son of a minor nobleman and belonged to a family that had produced a number of
learned men. At the age of eight, he was enrolled in the Jesuit school of La
Fleche in Anjou, where he remained for eight years. Besides the usual classical
studies, he received instruction in math and in Scholastic philosophy. Roman
Catholicism exerted a strong influence on Descartes throughout his life. Upon
graduation from school, he studied law at the University of Poitiers, graduating
in 1616. He never practiced law, however--in 1618 he entered the service of
Prince Maurice of Nassau at Breda, Netherlands, with the intention of following
a military career. In succeeding years Descartes served in other armies, but
his attention had already been attracted to the problems of mathematics and
philosophy to which he was to devote the rest of his life. He made a pilgrimage
to Italy in 1623-24, and spent the years from 1624 to 1628 in France. While in
France, he devoted himself to the study of philosophy and also experimented in
optics. In 1628, having sold his properties in France, he moved to the
Netherlands, where he spent most of the rest of his life. He lived for varying
periods in a number of different cities in the Netherlands, including Amsterdam,
Deventer, Utrecht, and Leiden.
It was probably during the first years of his residence in the
Netherlands that Descartes wrote his first major work, Essais philosophiques,
published in 1637. The work contained four parts: an essay on geometry,
another on optics, a third on meteors, and Discours de la methode (Discourse on
Method), which described his philosophical theories. This was followed by other
philosophical works, among them Meditationes de Prima Philosophia (Meditations
on First Philosophy, 1641) and Principia Philosophiae (The Principles of
Philosophy, 1644). The latter volume was dedicated to Princess Elizabeth Stuart
of Bohemia, who lived in the Netherlands and with whom Descartes had formed a
deep friendship. In 1649, Descartes was invited to the court of Queen Christina
of Sweden in Stockholm to give the queen instruction in philosophy. The rigors
of the northern winter brought on the pneumonia that caused his death on
February 1, 1650.
The most notable contribution that Descartes made to mathematics was the
systematization of analytic geometry. He was the first mathematician to attempt
to classify curves according to the types of equations that produce them. He
also made contributions to the theory of equations and succeeded in proving the
impossibility of trisecting the angle and doubling the cube. Descartes was the
first to use the last letters of the alphabet to designate unknown quantities
and the first letters to represent the known ones. He also invented the “method
of indices” to express the powers of numbers. In addition, he formulated the
rule, which is known as Descartes\' rule of signs, for finding the number of
positive and negative roots for any algebraic equation.
Descartes\' philosophy, sometimes called Cartesians, carried him into
elaborate and erroneous explanations of a number of physical phenomena. These
explanations, however, had value, because he substituted a system of mechanical
interpretations of physical phenomena for the vague spiritual concepts of most
earlier writers. Although he had at first been inclined to accept the theory
proposed by Copernicus regarding the universe as a heliocentric one, he
abandoned this theory when it was pronounced heretical by the Roman Catholic
church. In its place he devised a theory of vortices in which space was
entirely filled with matter, in various states, whirling about the sun. In the
field of physiology, Descartes held that part of the blood was a “subtle fluid,”
which he called animal spirits. He believed the animal spirits came into
contact with “thinking substances” in the brain and flowed out along the
channels of the nerves to animate the muscles and other parts of the body. His
study of optics led him to the independent discovery of the fundamental law of
reflection: that the angle of incidence is equal to the angle of reflection.
His essay on optics was the first published statement of this law. Descartes\'
treatment of light as a type of pressure in a solid medium paved the way for the
“undulatory theory of light.”
Descartes attempted to apply the rational inductive methods of science,
and particularly of mathematics, to philosophy. Before his time, philosophy had
been dominated by the method of Scholasticism, which was entirely based on
comparing and contrasting the view of recognized authorities. Rejecting this
method, Descartes stated, “In our search for the direct road to truth, we should