born June 23, 1912, London, Eng.
died June 7, 1954, Wilmslow, Cheshire
English mathematician and logician.
He studied at the Universityof Cambridge and at Princeton's Institute for Advanced Study. In his seminal 1936 paper "On Computable Numbers," he proved that there cannot exist any universal algorithmic method of determining truth in mathematics and that mathematics will always contain undecidable (as opposed to unknown) propositions. That paper also introduced the Turing machine . He believed that computers eventually would be capable of thought indistinguishable from that of a human and proposed a simple test (see Turing test ) to assess this capability. His papers on the subject are widely acknowledged as the foundation of research in cryptography during World War II; after the war he taught at the University of Manchester. His apparent suicide at 41 followed an arrest for homosexual acts and extreme medical treatments aimed at changing his sexual orientation.