Pierre de Fermat (; 17 August 1601 – 12 January 1665) was a
French lawyer at the
Parlement of
Toulouse,
France, and a
mathematician who is given credit for early developments that led to
infinitesimal calculus, including his technique of
adequality. In particular, he is recognized for his discovery of an original method of finding the greatest and the smallest
ordinates of curved lines, which is analogous to that of the
differential calculus, then unknown, and his research into
number theory. He made notable contributions to
analytic geometry,
probability, and
optics. He is best known for
Fermat's Last Theorem, which he described in a note at the margin of a copy of
Diophantus'
Arithmetica.