Pierre de Fermat
The French mathematician Pierre de Fermat (1601- 1665). Fermat never published his work in the usual sense and his results are known through his letters to friends, notes in book margins and challenges to other mathematicians. He worked on the theory of probability in which he corresponded with Pascal and on analytical geometry. In optics he devised the Fermat's principle and used it to deduce the laws of reflection and refraction of light. He also worked on the theory of equations and numbers. Fermat's Last Theorem puzzled mathematicians for over 300 years, until proved by Andrew Wiles in 1993. Fermat claimed to have found a proof but never published it.