# Fermat, Pierre de[fermah](1601--65) Mathematician, born in Beaumont-de-Lomagne, S France. He studied law at Toulouse, where he became a councillor of parliament. His passion was mathematics, most of his work being communicated in letters to friends containing results without proof. His correspondence with Pascal marks the foundation of probability theory. He studied maximum and minimum values of functions in advance of the differential calculus, but is best known for his work in number theory, the proofs of many of his discoveries being first published by Leonhard Euler a hundred years later. His "last theorem' was the most famous unsolved problem in mathematics: it states that there are no integers positive *x*, *y*, and *z* with *x*^{n}+*y*^{n}=^{z}*n* if n is greater than 2; a proof was announced by British mathematician Andrew Wiles in 1993. In optics, *Fermat's principle* was the first statement of a variational principle in physics: the path taken by a ray of light between two given points is the one in which the light takes the least time compared with any other possible path. |