Pierre de Fermat

The 'prince of amateurs' who left the hardest problem in a margin

Fermat was a French magistrate by profession who, doing mathematics as a hobby, laid the foundations of modern number theory. In letters exchanged with Pascal he helped give birth to probability theory, and independently of Descartes he arrived at the ideas of analytic geometry. His 'Last Theorem,' scribbled in a margin 'too narrow to contain the proof,' went unsolved for 358 years.