Pierre de Fermat

Pierre de Fermat (1607–1665) practiced law as a magistrate of the Parlement of Toulouse, doing mathematics in his leisure hours as the greatest 'amateur' in scientific history. Communicating his discoveries through letters to Mersenne, Pascal, and Descartes, he pioneered coordinate geometry independently of Descartes.

In optics, Fermat's Principle established that light travels between two points along the path that takes the least time, deriving Snell's law of refraction. In number theory, he formulated Fermat's Little Theorem and his legendary 'Last Theorem' ($a^n + b^n = c^n$ has no positive integer solutions for $n > 2$), jotted in the margin of Diophantus's *Arithmetica*, which remained unsolved for 358 years until Andrew Wiles proved it in 1995.