(1601–65). One of the leading mathematicians of the 17th century was the Frenchman Pierre de Fermat. His work was all the more remarkable because mathematics was only his hobby. His profession was law. Independently of his great contemporary, René Descartes, he discovered the fundamental principles of analytic geometry. He is also regarded as the inventor of differential calculus, and in association with Blaise Pascal, he was a cofounder of the theory of probability.
Pierre de Fermat is reported to have been born on Aug. 17, 1601, in Beaumont-de-Lomagne, France. He studied law and received his degree from the University of Orléans in 1631. He served in the legislature at Toulouse and was named to the criminal court in 1638. He henceforth made his living as a jurist. Fermat seldom gave proofs of his many mathematical theories, but his work was taken up and elaborated by other great mathematicians such as Christiaan Huygens, Gottfried Leibniz, Isaac Newton, Leonhard Euler, and Carl Friedrich Gauss. Much of his work was published by his son in 1679 under the title Opera mathematica (Mathematical Works).