The enigma of intelligence


NO, says the computer at Hodges Figgis, they don't have a copy of Alan Turing: The Enigma in stock. Meanwhile the computer in Waterstones, faking a higher degree of intelligence, insists there are two copies left - but a 10-minute search by a helpful assistant is in vain.

No, Alan Turing (1912-1954) isn't exactly the height of fashion at the moment. No, rarely will you find him jostling with the Darwins and Dawkins and Hawkings in the "popular science" sections of our capital's bookshops.

Or maybe I'm exaggerating a bit. Alan Turing: The Enigma has sold a respectable 68,000 copies around the world. The biography has inspired an acclaimed play and a new feature film on the BBC next week, all highlighting a unique hero of computing history.

Besides inventing the modern computer as we know it, the eccentric, long-distance-running, maverick mathematician changed the course of the second World War. He also laid down several helpful routes for later generations to come to grips with machine intelligence".

Breaking the code

But all this was still a long way off during the darkest days of the war in the North Atlantic. The German U-boat packs were picking off the Allied convoys, and Britain was close to collapse.

The submarines' movements couldn't be deduced from their radio traffic, because the most powerful encryption devices ever known, the Germans' "Enigma" machines, generated what seemed to be an unbreakable code.

Meanwhile some of Britain's best mathematicians and cryptographers had been assembled at a top-secret cypher school at Bletchley Park in Buckinghamshire (deliberately chosen because it was halfway between Oxford and Cambridge universities). Turing and his colleagues set about constructing a series of machines that could make the complex computations required at amazing speeds.

Soon the contraptions, tended by Turing's vast army of female assistants, were able to decode the messages within hours instead of weeks. Then they could correlate any mysterious coordinates in the messages with the actual locations of ships that were sunk.

As one reviewer of the Turing biography put it, once this second layer of code had been peeled off, "it was as if all of a sudden, the German fleet in the Atlantic were simply displayed on a screen in front of them."

One size fits all

Turing's wartime codebreaking exploits convinced him of the speed and reliability of electronics, and how computers could manipulate not just arithmetic but symbols of any kind, from chess-playing to conversations.

While Bletchley had special machines organised to de different tasks, now Turing argued that they could all be replaced by programs for a single "universal machine".

As his biographer Andrew Hodges argues so forcefully today: "In 1945 Alan Turing alone grasped everything that was to change computing completely after that date: the universality of his design, the emphasis on programming, the importance of non-numerical applications, the apparently open-ended scope for mechanising intelligence. He did not do so as an isolated dreamer, but as someone who knew about the practicability of large-scale electronics, with hands-on experience."

After drawing up the most detailed designs then in existence, Turing fell out of favour with the "proper" intellectual circles. By the late 1940s he was so marginalised that he "retreated" (as some argued) into more theoretical work, particularly in artificial intelligence.

A tragic end

But why have all his achievements in philosophy, mathematics and computing been relatively downplayed?

For several decades Turing's role at Bletchley was obviously shrouded by Britain's Official Secrets Acts. Furthermore, the American revisionists of computer history passed him by (and though his biography has been translated into several other languages, it's now out of print in the US).

On top of all that, Turing was gay. He was painfully honest about his homosexuality, as the new film on BBC 1 next Wednesday points out, but his life ended in extremely tragic circumstances. In 1952 he was convicted of being involved in "unnatural acts". Such was the state of British justice (and medicine) at the time that he was required to take female hormones. Besides the distressing physical side-effects, he became severely depressed. Two years later he died by cyanide poisoning, almost certainly by suicide.

The Turing Test

The world lost a mathematical genius at the height of his powers, but his legacy lives on - particularly in his later theoretical work such as the "Turing Test" and the "Imitation Game".

Instead of getting bogged down in what a machine based intelligence might look like, or emotionally charged questions such as "can a machine think?", Turing suggested a series of simple but very clever games.

First, imagine that a man and a woman are in separate rooms and can be interrogated by a third party in another room again via a network terminal (or as Turing put it at the time, a teletype machine). This interrogator has to determine which room the woman is in, merely from the written replies.

Meanwhile the man tries to hoodwink the interrogator into thinking he's a woman, while the woman tries to help the interrogator as much as she can through her answers.

So far, we have a clever little game of sex roles, far more interesting than the formulaic rubbish of BlindDate, and Turing's biographer even draws parallels with all those gender-swapping games on Internet Relay Chat. But then Turing adds another clever twist the "Turing Test".

This time we have a human and a machine in different rooms (instead of the man versus the woman). Now the machine and the person "battle" to convince the interrogator that they are the human being and not a machine.

Since he proposed the Turing Test almost 50 years ago, it has been tried out on more and more sophisticated computer programs. While the test underscores the complexities and frailties of human language and knowledge-systems, it has become a major milestone in re-defining scientists' conceptions of artificial intelligence.


Turing's life story became much better known after the publication in 1983 of Alan Turing: The Enigma. Besides being a piece of exemplary scholarship about an extraordinary scientific mind, Andrew Hodges's study set "a new standard in writing about gay people in the past", as one reviewer wrote at the time.

The biography also inspired Douglas Hofstadter's influential review (and many follow-up articles) in the Scientific American. Then it led to Hugh Whitmore's West End and Broadway hit, Breaking the Code. Derek Jacobi returns to his role as Turing in the BBC's film adaptation of the stage play, a coproduction with WGBH Boston. Prunella Scales plays Turing's protective mother, and watch out for a rare acting appearance by that other old enigma himself, the playwright Harold Pinter.