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EARLY LIFEThe son of a British member of the Indian civil service, Turing entered King's College, University of Cambridge, to study mathematics in 1931. After graduating in 1934, Turing was elected to a fellowship at King's College in recognition of his research in probability theory. In 1936 Turing's seminal paper On Computable Numbers, with an Application to the Entscheidungsproblem [Decision Problem] was recommended for publication by the American mathematician-logician Alonzo Church, who had himself just published a paper that reached the same conclusion as Turing's. Later that year, Turing moved to Princeton University to study for a Ph.D. in mathematical logic under Church's direction (completed in 1938). The Entscheidungsproblem seeks an effective method for deciding which mathematical statements are provable within a given formal mathematical system and which are not. In 1936 Turing and Church independently showed that in general this problem has no solution, proving that no consistent formal system of arithmetic is decidable. This claim is now known as Church's thesis - or as the Church-Turing thesis when stated in the form that any effectively calculable function can be calculated by a universal Turing machine, a type of abstract computer that Turing had introduced in the course of his proof. |