John Wallis

John Wallis, who lived from 1616 to 1703, was an English clergyman and mathematician who is given partial credit for the development of infinitesimal calculus. Born in Ashford, Kent, he studied at Emmanuel College, Cambridge, took his Master's degree in 1640 and then entered the priesthood. Between 1643 and 1689 he served as chief cryptographer for Parliament and, later, the royal court, and he joined the group of scientists that was later to evolve into the Royal Society. In 1649 he was appointed to the Savilian Chair of Geometry at Oxford University, where he lived until his death. He extended Cavalieri's method of indivisibles through the use of interpolation, applied Kepler's principle of continuity to develop techniques for the evaluation of integrals, and is credited with introducing the symbol for infinity. Besides his mathematical works he wrote on theology, logic, English grammar and philosophy.