Castrated by a grateful nation

Some people’s lives drive you into a rage. Alan Turing’s is one. In The Man Who Knew Too Much David Leavitt unexpectedly compares him to Alec Guinness playing Sidney Stratton in The Man in the White Suit. Like Stratton, who invented a suit that would never wear out, Turing was a brilliant scientific deviant, interested in ‘welding the theoretical to the practical, approaching mathematics from a perspective that reflected the industrial ethos of the England in which he was raised’. And, like Stratton, he was ‘hounded out of the world’. But Stratton was playing an Ealing comedy. The injustice done to Turing makes you want to spit at someone. Snow White and the Seven Dwarfs was Turing’s favourite film. He was especially fond of a scene in which the Wicked Queen coats an apple in poison to give to Snow White.

Turing’s first great mathematical contribution followed shortly after Gödel’s Incompleteness Theorem and used similar unseemly mathematical techniques. Gödel proved that no mathematical system can ever be shown to be consistent or complete. Turing, by imagining a room filled with strange machines that could analyse every possible mathematical equation, showed that no mathematical system can provide a general method for testing the truth or falsehood of its theorems. With Gödel and Turing, the certitude of mathematics disappeared. Leavitt spends 40 pages describing straightforwardly how Turing managed to prove this thesis. They should be reread two or three times, and mulled over like a good puzzle. How could something that begins so simply turn out so destructive to mathematical divinity? I’m on my fourth reading, and still don’t quite get it.