The English mathematician Alan Turing is best known for his pioneering work in the area of computers and artificial intelligence. His concept of the Universal Turing Machine helped the allies break the German Enigma code in WWII, and his inquiries into artificial intelligence established the core theoretical and philosophical problems for AI research.
Turing was born into a middle-class English family, both parents being involved with the British colony in India. He was left in the care of another couple when his parents returned to India in 1913, and this, along with the realization of his own homosexuality as he grew older, caused Turing to develop an aloof nature and a disregard for social niceties. As a boy his intelligence was displayed through his interest in organic chemistry and cryptography, though he also showed an impatience for learning fundamentals when deeper problems piqued his interest.
In 1931 Turing won a scholarship in mathematics to King's College, Cambridge, where he became fascinated with problems of mathematical logic. While working on problems associated with Gödel's theorem, Turing first theorized the Turing Machine. Such a machine could be fed instructions on a paper tape, perform calculations, and present an answer. These calculations could be anything from the solution to a math problem, to how to play chess. The Universal Turing Machine could be programmed to imitate the behavior of any other type of calculating machine, just as a personal computer today can be programmed with software to act as a calculator, word processor, or game. The results of Turing's research were published in the paper "On Computable Numbers, with an application to the Entscheidungs problem," and were immediately recognized as major breakthroughs in the area of machine computing.
In WWII Turing was enlisted to help crack the Enigma code created by the Germans. To this end, he worked with a group of British mathematicians and engineers to create Colossus, arguably the first electronic Universal Turing Machine. Using Colossus, Turing and his team were able to break the code and provide the Allies with intelligence information that was critical in winning the war.
In 1948 Turing became Deputy Director of the computer laboratory at Manchester University, home of MADAM, the Manchester Automatic Digital Machine, the first functional digital machine that ran a stored program. Turing taught MADAM to play chess and write love letters, and in 1950 he published "Computing Machinery and Intelligence." Here he presented the "Turing test" as a means of demonstrating that machines could display the same intelligence as humans. In this test, a human being interrogates a machine using a keyboard and monitor. Turing thought that as long as the machine could imitate a human response to a question, it should be considered intelligent, because this was the standard by which humans judged other beings to have intelligence. Turing dedicated the rest of his career to fundamental questions on the nature of intelligence and its artificial creation.
The complication in Turing's career was his homosexuality, which was still illegal and socially unacceptable. In 1952, Turing was arrested on charges of "gross indecency," put on probation, and forced to undergo hormone treatments. The treatment had disastrous physical consequences for Turing, and his career suffered as well. In 1954, following a deep depression, Turing committed suicide by eating a poisoned apple.
Turing's impact on the world of computing and artificial intelligence is incalculable. His Universal Turing Machine is the forerunner of today's personal computer, and his work in the area of artificial intelligence laid the groundwork for today's research. More important, however, are the philosophic questions that Turing raised about what it means to be a human being.