René Descartes, French mathematician and philosopher (died 1650)

René Descartes was a French philosopher, scientist, and mathematician, widely considered a seminal figure in the emergence of modern philosophy and science. Mathematics was paramount to his method of inquiry, and he connected the previously separate fields of geometry and algebra into analytic geometry.

March 31 is the 90th day of the year in the Gregorian calendar; 275 days remain until the end of the year.