Mathematician who developed calculus and who introduced the symbol for 'infinity', ∞
John Wallis, 'the greatest of Newton's precursors in mathematics', did not begin to learn arithmetic until the age of fifteen; but academic education in his day usually neglected mathematics entirely, as something for tradesmen and navigators. Wallis first found time for it because by fourteen, when he went to Felsted School, he had already learned as much of Latin, Greek, Hebrew, French, logic, and music, as most university students. In his Emmanuel days (1632-1640) he also read medicine and anatomy.
He was ordained in 1640, and at first held several private chaplaincies. While in the household of Lord Vere, in 1642, he deciphered a secret letter relating to the capture of Chichester. The feat made his name, and his skill as a code-breaker was much used by the Parliamentarians, though he claimed later that he did not reveal to them nearly as much intercepted intelligence as he could have done. His politics have been described as devious, but not dishonest. He gave evidence against Archbishop Laud in 1644; but in 1649 he signed the remonstrance against the execution of Charles I. Cromwell respected him, and it was he who in 1649 appointed him to the Savilian Professorship of Geometry at Oxford. But he was not obliged to relinquish his offices at the Restoration.
From 1644 Wallis was secretary to the Westminster Assembly of Divines, and while in London associated much with Robert Boyle and others whose meetings led to the foundation of the Royal Society. (Other Emmanuel graduates in the group were the mathematician Samuel Foster and the anatomist William Croone.) Wallis's mathematical work made important advances: his Arithmetica infinitorum (1655) contained the germs of the integral and differential calculus; he introduced the symbol 8 for infinity; he wrote on gravitation; he evaluated p by the interpolation (his own word) of terms in infinite series. His capacity for mental calculation was prodigious: one sleepless night be extracted in his head the square root of a number of 53 digits, and next morning dictated a correct result to 27 places. He was a correspondent of leading continental mathematicians and astronomers such as Fermat and Huygens.
In another field, Wallis wrote a book on English grammar (1652), with an appendix on the production of speech-sounds, from which he went on to develop a method of teaching the deaf and dumb to talk.
Among Wallis' s London friends was Samuel Pepys, who commissioned Kneller to paint his full-length portrait to hang in the Bodleian at Oxford.