The New York Review of Books

Cambridge University has always been hospitable to powerful but eccentric intellects. Again and again, solitary Cambridge thinkers have conceived, and given clear definitions to, the new ideas of later generations. One may think of young Isaac Newton, banished home to Lincolnshire in the 1660s to sit out the Great Plague; or of Charles Darwin in the 1840s and 1850s, back from the Beagle circumnavigation and wandering in the chalk hills around his house at Downe in Kent. Conversely, Cambridge tends to be a bit out of touch with worldly things. (“Oxford men think the world belongs to them,” the saying was, “Cambridge men don’t care who it belongs to.”) At best, the luminaries of Cambridge expected to deal with the world on their own idiosyncratic terms. So Newton became an autocratic Master of the Mint and lifelong president of the Royal Society; while, after a short spell as secretary of the Geological Society of London, Darwin retired to the country and enjoyed just that degree of ill health he needed in order to protect himself from intrusions that would interrupt his scientific writing.

Now, as Andrew Hodges’s remarkable biography makes clear, we may add another figure to this Cambridge pantheon: Alan Turing, newly elected a Fellow of King’s at the age of twenty-two, lying in a meadow near Grantchester in the summer of 1935, and dreaming up the arguments that would become essential points of departure for our own new world of information processing and “thinking machines.” Only, in Turing’s case, there is a mystery.

In relation to his own times, he had an intellect as radical, direct, and free of fog as any of his forerunners; and one would expect that now, at seventyone, he would be a pundit of British science, a public figure, even a life peer, celebrated not only for his ideas on artificial intelligence but for his secret work cracking the German “Enigma” codes during World War II. If all had gone well for him, he would be living a productive old age, as Baron Turing, former president of the Royal Society. But all did not go well for him. Instead, he has been dead for some thirty years, and his role in shaping our current modes of thought is half-forgotten. He died of cyanide poisoning in 1954, in his early forties, almost certainly a suicide, two years after being convicted under England’s antiquated laws against homo-sexual activity, and subjected, as the alternative to a prison term, to a year of androgynizing hormone treatment.

How did a life of such distinction end in a wreck? Until Andrew Hodges gave us the results of his inquiries, that question remained (as this book’s punning title suggests) an enigma. But, as happens rarely, an extraordinary thinker has found an ideal biographer. Andrew Hodges’s sympathetic and perceptive account traces both the professional and personal strands in Alan Turing’s life, death, and subsequent reputation; and he shows us how things went for …