The French philosopher and mathematician René Descartes was born on 31 March 1596 at La Haye, in Touraine, France. At age eight he entered the Jesuit College at La Flèche, where he developed a lasting interest in mathematics. In 1612 he began law studies at the University in Poitier, graduating four years later. He then followed along as military engineer with the army of the Prince of Nassau, returning to France in 1622. He then traveled across Europe until settling in the Netherlands in 1629. In 1649 he moved to Stockholm, Sweden, as private instructor to Queen Christina. He died there on 11 February 1650, of a severe cold his first biographers blamed on the harsh Swedish winter.

In 1644 Descartes published his famed *Principia Philosophiae*, a work that attracted considerable interest and is said to have greatly hindered the acceptance of Isaac Newton's mechanical philosophy on the continent, and especially in France. Descartes' basic tenet was that knowledge of the universe could be obtained from "*a priori*" mathematical reasoning.

Unlike his cosmological speculations, Descartes contributions to mathematics have stood the test of time. His greatest achievement his his development of analytic geometry, where geometrical objects are reduced to numbers, and algebraic techniques are used to produce mathematical counterparts to geometrical objects — for example, mathematical expressions describing curves such as parabolae, hyperbolae, and so on.

Descartes was a closet Copernican who was said to have been greatly scared by the fate of Galileo, to the point of shelving a planned cosmological treatise based on the "*Copernican hypothesis (planetary model)*". He did make some important contributions to physics, in particular with the co-discovery of the sine law of refraction.

Porter, R. (ed.) 1994,The Biographical Dictionary of Scientists, Oxford University Press.

Wednesday, April 29, 2015