René Descartes built the foundation for modern philosophical method with a simple catchphrase: "I think, therefore I am." He is also regarded as the founder of analytic geometry.

Every time you graph an equation on a Cartesian coordinate system, you are using the work of René Descartes. Descartes, a French mathematician and philosopher, was born in La Haye, France (now named in his honor) on March 31, 1596. His parents taught him at home until he was 8 years old, when he entered the Jesuit college of La Flèche. There he continued his studies until he graduated at age 18.

Descartes was an outstanding student at La Flèche, especially in mathematics. Because of his delicate health, his teachers allowed him to stay in bed until late morning. Despite missing most of his morning classes, Descartes was able to keep up with his...