FERMAT, PIERRE DE

born Aug. 17, 1601, Beaumont-de-Lomagne, France died Jan. 12, 1665, Castres French mathematician who is often called the founder of the modern theory of numbers. Together with Ren Descartes, Fermat was one of the two leading mathematicians of the first half of the 17th century. Independently of Descartes, Fermat discovered the fundamental principle of analytic geometry. His methods for finding tangents to curves and their maximum and minimum points led him to be regarded as the inventor of the differential calculus. Through his correspondence with Blaise Pascal he was a co-founder of the theory of probability. Additional reading A substantial and authoritative summary of Fermat's achievements is provided in Michael S. Mahoney, The Mathematical Career of Pierre de Fermat (16011665) (1973). More specialized aspects of Fermat's work are treated in Carl B. Boyer, History of Analytic Geometry (1956, reissued 1988), and The Concepts of the Calculus (1949, reissued as The History of the Calculus and Its Conceptual Development, 1959); and Isaac Todhunter, A History of the Mathematical Theory of Probability from the Time of Pascal to That of Laplace (1865, reprinted 1965).