Pierre de Fermat (1601-1665), French mathematician and physical theorist. Fermat's results (often without proofs) are known through his letters to friends. He corresponded on probability theory with Pascal, and also worked on number theory, early calculus, and analytical geometry. The proofs for Fermat's work were largely published by Euler, but Fermat's Last Theorem was not proved until 1993 (by Andrew Wiles). In physics, Fermat devised Fermat's principle to derive the path taken by light rays. The Latin inscription refers to his profession as a lawyer in Toulouse. Frontispiece from Fermat's posthumous work 'Varia opera mathematica' (1679).