René Descartes (1596–1650) was born in La Haye (now Descartes), France, on March 31, and he died in Stockholm, Sweden, on February 11. Although of Roman Catholic heritage, he lived in a region controlled by Protestant Huguenots at a time when Protestants and Catholics were frequently at war. His inherited wealth allowed him freedom to study and travel around Europe. He made important contributions to metaphysics, mathematics, and physiology. In mathematics, he invented coordinate geometry, which combines algebra and geometry into a powerful tool for the mathematical study of the physical world. Although he offered proofs for the existence of God and the immortality of the soul, he was suspected of being an atheistic materialist, and lived in fear of persecution. When Galileo Galilei (1564–1642) was condemned in 1633 as a heretic for teaching that the earth revolved around the sun, Descartes suppressed any publication of his...