FERMAT, PIERRE (1601-1665), French mathematician, was born on Aug. 17, 1601, at Beaumont-de-Lomagne near Mon tauban. In his youth, with Pascal, he made discoveries about the properties of numbers, on which he later built his method of calculating probabilities. His book De maximis et minimis caused a dispute with Descartes. His brilliant researches in the theory of numbers entitle him to rank as the founder of the modern theory. They were made, and in 167o published by his son, in the form of notes on Diophantus. Other theorems were published in his Opera Varia, and in John Wallis's Commercium epistolicum (1658). He also studied the reflection of light (q.v.) and enunciated his principle of least time. For Fermat's Last Theorem see below.
Fermat was a councillor for the parliament of Toulouse, dis tinguished both for legal knowledge and for strict integrity of conduct. He was also an accomplished general scholar and lin guist. He died at Castres, near Toulouse, on Jan. 12, 1665.
The Opera mathematica of Fermat were published at Toulouse, in 2 vols. folio, 167o and 1679. The Oeuvres of Fermat, including not only the Opera mathematica, but his correspondence with Descartes, Pascal and others, were edited by P. Tannery and C. Henry (Paris,