Rene Descartes spent most of his childhood in solitude, a situation that also came to characterize his adult life. Fortunately, these countless lonely hours helped Descartes produce the declaration that changed all philosophy: "I think, therefore I am." Eventually convincing himself to doubt and disregard sensory knowledge, Descartes found he could prove his existence through his thoughts. This internal information, he believed, was the true reality and external forces were hopelessly deceiving.

In Descartes in 90 Minutes, Paul Strathern offers a concise, expert account of Descartes' life and ideas and explains their influence on man's struggle to understand his existence in the world. The book also includes selections from Descartes' work, a brief list of suggested readings for those who wish to delve deeper, and chronologies that place Descartes within his own age and in the broader scheme of philosophy.