Alan Turing

Times obituary

Dr. Alan Mathison Turing, O.B.E., F.R.S., whose death at the age of 41 has already been reported, was born on June 23, 1912, the son of Julius Mathison Turing.

He was educated at Sherborne School and at King's College, Cambridge, of which he was elected a Fellow in 1935. He was appointed O.B.E. in 1941 for wartime services in the Foreign Office and was elected F.R.S. in 1951. Until 1939 he was a pure mathematician and logician, but after the war most of his work was connected with the design and use of automatic computing machines, first at the National Physical Laboratory and then since 1948 at Manchester University, where he was a Reader at the time of his death.

The discovery that would give Turing a permanent place in mathematical logic was made not long after he had graduated. This was his proof that (contrary to the then prevailing view of Hilbert and his school at Göttingen) there are classes of mathematical problems that cannot be solved by any fixed and definite process. The crucial step in his proof was to clarify the notion of a "definite process," which he interpreted as "something that could be done by an automatic machine." Although other proofs of insolubility were published at about the same time by other authors, the "Turing machine" has remained the most vivid, and in many ways the most convincing, interpretation of these essentially equivalent theories. The description that he then gave of a "universal" computing machine was entirely theoretical in purpose, but Turing's strong interest in all kinds of practical experiment made him even then interested in the possibility of actually constructing a machine along these lines.

It was natural at the end of the war for him to accept an invitation to work at the National Physical Laboratory on the development of the ACE, the first large computer to be begun in this country. He threw himself into the work with enthusiasm, thoroughly enjoying the rapid alternation of abstract questions of design with problems of practical engineering. Later at Manchester, he devoted himself more particularly to problems arising from the use of the machine. It was at this time that he became involved in discussions on the contrasts and similarities between machines and brains. Turing's view, expressed with great force and wit, was that it was for those who saw an unbridgeable gap between the two to say just where the difference lay.

The war interrupted Turing's mathematical career for the six critical years between the ages of 27 and 33. A mathematical theory of the chemical basis of organic growth, which he had lately started to develop, has been tragically interrupted and must remain a fragment. Though his contributions to logic have been important, few who have known him personally can doubt that, with his deep insight into the principles of mathematics and natural science, and his brilliant originality, he would, but for these accidents, have made much greater discoveries.

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