Turing, Alan Mathison, 1912–54, British mathematician and computer theorist. While studying at Cambridge he began work in predicate logic that led to a proof (1937) that some mathematical problems are not susceptible to solution by automated computation; in arriving at this, he postulated a universal machine, now called a Turing machine, that was the theoretical prototype of the electronic digital computer. After completing a Ph.D. at Princeton (1938), he returned home to England, where, during World War II, he was instrumental in deciphering German messages encrypted by the Enigma cipher machine. After the war, he helped design computers, first for the British government (1945–48) and then for the Univ. of Manchester (1948–54). During this period, he produced a body of work that helped form the basis of the newly emerging field of artificial intelligence; among his contributions was the Turing test, a procedure to test whether a computer is capable of humanlike thought. Two years after being arrested for a homosexual offense (and then undergoing chemical castration as a "treatment"), he died of cyanide poisoning. His death was ruled a suicide at the time, but the exact circumstances of his death are unclear, and it has been argued that it could have been accidental. In 2013 Turing was posthumously pardoned for his 1952 conviction for homosexuality.

See biographies by S. Turing (his mother, 1959, rev. ed. 2012) and A. Hodges (1983, repr. 2012)); G. Dyson, *Turing's Cathedral: The Origins of the Digital Universe* (2012).

*The Columbia Electronic Encyclopedia,* 6th ed. Copyright © 2012, Columbia University Press. All rights reserved.