Book review: The man who knew too much

Estimated read time: 4-5 minutes

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THE MAN WHO KNEW TOO MUCH Alan Turing and the Invention of the Computer

By David Leavitt 319 pages. $22.95. Atlas Books/W.W. $ Norton & Co. Reviewed by George Johnson

Maybe it's because I already knew the story about the tragic genius who revolutionized mathematics, helped the British crack secret Nazi codes and died after biting into a poisoned apple. Or maybe I was just in the mood for fiction.

For some reason, about halfway through David Leavitt's short, readable life of Alan Turing, I put the book aside and turned instead to his most recent novel, "The Body of Jonah Boyd."

It is actually a novel within a novel, ending with a self- referential twist that made me wonder whether Leavitt had been inspired by Turing's dizzying proof about undecidability in mathematics, in which a computer tries to swallow its own tail.

Turing was a fellow at King's College, Cambridge, in 1936, when he confronted what might be called the mathematician's nightmare: the possibility of blindly devoting your life to what, unbeknownst to anyone but God, is an unsolvable problem. Turing's stroke of genius was to recast the issue mathematicians call it the decision problem in mechanical terms. A theorem and the instructions for proving it, he realized, could be thought of as input for a machine. If there was a solution, Turing's imaginary device would eventually come to a stop and print the answer. Otherwise it would grind away forever. Although it was not his primary intention, he had discovered, in passing, the idea of the programmable computer.

In "The Man Who Knew Too Much," Leavitt is faced with the task of giving a new shine to a life that has been scrutinized several times before. Turing's mother, Sara, wrote her own account shortly after his death, and in 1983 Andrew Hodges provided the definitive biography, with "Alan Turing: The Enigma." Inspired by Hodges, Hugh Whitemore turned the story into a play, "Breaking the Code," with Derek Jacobi in the starring role of the premiere.

What made Turing's story compelling enough for Broadway happened after his groundbreaking work at Cambridge. Hooked on the idea of mechanical problem-solvers, he helped design the machinery that deciphered the Germans' battle-front communications, an important factor in the Allied victory. After the war he helped develop the first modern digital computers and made his mark as a leading advocate of the notion that the brain is a computer and machines can think.

A solitary, introspective man, he was quietly working at the University of Manchester when he was arrested for being a homosexual. Two years later he was found dead with that apple, an apparent suicide. While the book is a skillful, literate compression, as I made my way toward the end I never felt that Leavitt succeeded in inhabiting the story, making the fantastic world of Turing as captivating as that of the fictional Jonah Boyd.

The author certainly can't be accused of shirking the mathematics. Turing's proof and his work on cryptanalysis are described at an impressively fine grain. And some of the Cambridge scenes have a writerly touch. Frequently turning to E.M. Forster's novel "Maurice," Leavitt evokes what it might have been like to be a lonely young homosexual at King's College, and his description of Turing's classroom dialogues with the enigmatic Ludwig Wittgenstein reads like a Beckett play.

The circumstances surrounding Turing's demise are murky enough that some people doubt he really killed himself. He had been using potassium cyanide in gold-plating experiments. The poisoning was conceivably accidental. Leavitt entertains, though not so seriously, another possibility: "that the suicide was staged," and he had become, like the Hitchcock character, "a man who knew too much." More likely he was simply the man who couldn't connect, who decided in the end, as Leavitt beautifully puts it, "to camp it up a bit to invest his departure from a world that had treated him shabbily with some of the gothic, eerie, colorful brilliance of a Disney film." One way or the other, his brain got caught in one of those inescapable loops. The cause of his death is an undecidable problem.

George Johnson's most recent book is "Miss Leavitt's Stars: The Untold Story of the Woman Who Discovered How to Measure the Universe."