For Alan Turing’s many admirers, the centenary of his birth on Saturday is an occasion for both celebration and mourning. Here, after all, is the architect of the modern computer, the code-breaker whose ingenuity ensured an Allied victory in World War II and the father of artificial intelligence. Yet Turing was also a victim of a pernicious and paranoid strain of sexual hypocrisy in 20th-century England. Nor, in the 21st, has the victimization wholly ceased.
Turing’s remarkable career was marked by happenstance. In 1936, when he was a student at Cambridge, he attended a lecture in which M.H.A. “Max” Newman characterized an old and thorny logic problem as a matter of finding a “mechanical process” for testing the validity of a mathematical assertion. Turing took the phrase “mechanical process” at face value and wrote a paper in which he laid out the architecture of a hypothetical machine to do the testing — what became known as the “Turing machine.” The paper, intended for specialists, amounted to a blueprint for the modern computer, a “universal machine” that could do the work of an infinity of single-use machines.
The fortuitous breakthroughs continued. During World War II, Turing was among a group of thinkers summoned by the British government to Bletchley Park to help crack the seemingly airtight German Enigma code. Because the code was generated by a machine, Turing decided, only a machine could break it. He went on to design and help build that machine — the “Bombe,” without which the Allies might have lost the war — thereby instigating a huge leap forward in the field of cryptanalysis.
After the war Turing moved to Manchester, where he oversaw the construction of several of the first functioning computers and posited a test that could determine whether a machine could be said to think — the “Turing test.” In so doing, he created what we now call the field of artificial intelligence.
Any one of these achievements, in a single lifetime, would have been extraordinary. Yet Turing managed all three.
From early in his adolescence, Turing understood that he was gay and saw nothing wrong with it. If the society in which he lived criminalized homosexuality, he believed the fault lay with the society, not with the men and women it vilified. He made little effort to disguise or efface his desire for other men, and when, in the early 1950s, he embarked on a businesslike affair with a youth in Manchester, his sense of how the world should be clashed with how it was.
Suspecting his boyfriend of robbery, he summoned the police to his house. They ended up arresting Turing under the “blackmailer’s charter,” which criminalized “acts of gross indecency” between adult men in public or in private. It was under this law — not repealed until 1967 — that Oscar Wilde had been sentenced to hard labor in prison.
To avoid a similar fate, Turing agreed to submit to a course of estrogen therapy intended to cure him of his homosexuality; as a result, he grew breasts and became impotent. Yet even after the treatment ended, the police, fearing that he might defect to the Soviet Union, stayed on his trail, interrupting every effort he made to live life as he saw fit. In June 1954, Turing committed suicide by biting into an apple laced with cyanide — a nod to his favorite film, Walt Disney’s “Snow White and the Seven Dwarves.”
For much of the 20th century, Turing’s name was mentioned only in whispers. His contribution to the Bletchley Park effort remained classified, while credit for his groundbreaking work on the computer, as the scholar Martin Davis has shown, went largely to John von Neumann, whom Turing knew at Princeton’s Institute of Advanced Study.
All that kept Turing’s memory alive during those dark years was the dedication of his admirers, an unlikely coalition of mathematical logicians, gay rights advocates and gay rights advocates who were also mathematical logicians. Finally, in 2009, then-Prime Minister Gordon Brown issued an official apology to Turing and his family on behalf of the United Kingdom, instigating a movement to obtain an official pardon for Turing to mark the centenary of his birth.
In February, the Liberal Democrat Lord Sharkey introduced the possibility of a pardon in the House of Lords, only to have his proposal rebuffed by Lord McNally, the justice minister. McNally argued that Turing “was properly convicted of what at the time was a criminal offence. He would have known that his offence was against the law and that he would be prosecuted. It is tragic that Alan Turing was convicted of an offence which now seems both cruel and absurd — particularly poignant given his outstanding contribution to the war effort. However, the law at the time required a prosecution.”
As British lawmaker John Leechsubsequently noted, such was not the logic applied in the case of 300 World War I soldiers who had been executed for desertion and were pardoned posthumously in 2006. Most of these soldiers had suffered from shell shock. If they were deemed worthy of a pardon, why not Turing?
In a letter sent near the end of his life to his friend Norman Routledge, Turing, who on top of everything else was a gifted writer, crafted this mordant syllogism:
Turing believes machines think.
Turing lies with men.
Therefore machines cannot think.
What he feared most, in other words, was that his prosecution would be used as an excuse to kill his ideas. Thank God he was wrong.
Indeed, all one needs to do is look at an iPhone to see how thoroughly Turing’s concept of a “universal machine” has shaped our consciousness. Not only that, he is finally getting the recognition he deserves. On a visit in 2009 to Middlebury College, where professors Michael Olinick and Robert Martin were teaching a freshman seminar on Turing’s life and work, I met a group of bright undergraduates for whom Turing’s genius was as remarkable as his homosexuality was ordinary. One of these students told me that his ambition was to reinvigorate the field of artificial intelligence by returning to first principles — the principles that Turing laid out in his papers on the subject.
Whether or not the British Parliament erases his ludicrous conviction, it seems that Turing himself is unerasable. And that is reason to celebrate.
David Leavitt is a professor at the University of Florida and the author of “The Man Who Knew Too Much: Alan Turing and the Origins of the Computer.”