by Jack Copeland, Jonathan Bowen, Mark Sprevak and Robin Wilson, Oxford University Press
DURING the 20th century, any book calling itself The Turing Guide would have been inconceivable. But in 2017 we have a massive and extraordinarily wide-ranging volume about the life, work and influence of mathematician Alan Turing. This is despite his achievements being shrouded in official and personal secrecy at the time of his death in 1954, aged 41, and for decades afterwards. The new guide is the work of four editor-writers: Turing historian Jack Copeland, computer scientist Jonathan Bowen, philosopher Mark Sprevak and mathematician Robin Wilson.
In the 1960s, Turing was known only to a few mathematicians, computer scientists and philosophers 鈥� and to one science-fiction writer, Arthur C. Clarke. In his 1962 book Profiles of the Future, Clarke showed himself well informed about the Turing test for machine 鈥渢hinking鈥�, noting that: 鈥淎n electronic brain that passed this test would, surely鈥� be regarded as an intelligent entity鈥� 鈥� like the computer HAL that Clarke would soon imagine in 2001: A Space Odyssey.
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Turing encapsulated his own test in a humorous human-computer 鈥渃onversation鈥�, quoted in The Turing Guide. Human: 鈥淚n the first line of your sonnet which reads 鈥楽hall I compare thee to a summer鈥檚 day鈥�, would not 鈥榓 spring day鈥� do as well or better?鈥� Computer: 鈥淚t wouldn鈥檛 scan.鈥� Human: 鈥淗ow about 鈥榓 winter鈥檚 day鈥�? That would scan all right.鈥� Computer: 鈥淵es, but nobody wants to be compared to a winter鈥檚 day.鈥�
But Clarke on Turing the man was (given the time of writing) much less well informed. He was a 鈥渂rilliant mathematician鈥� who 鈥渇irst indicated how thinking machines might be built鈥� and then 鈥渟hot himself a few years after publishing his results鈥�.
Only between the 1970s and 2000 did a truer picture of Turing start to emerge, with the gradual declassification of the UK鈥檚 wartime codebreaking effort at Bletchley Park, and the publication in 1983 of Alan Turing: The enigma. This was an eye-opening biography by Andrew Hodges, a mathematician and gay rights activist, who provides a brief foreword to The Turing Guide.
A man of parts
This new version of Turing came in three parts. First, there is the theoretical founder of modern computing, with his 1936 paper 鈥淥n computable numbers鈥�. Then, there is the brain of recent plays and movies, which mostly focus on his key role in codebreaking, beginning with cracking the Enigma code in 1941 using the bombe, a machine he co-invented. Last, we have the man convicted of homosexual practices in 1952 and forced to take female hormones, and who fatally ingested cyanide at home probably by biting into a poisoned apple: a possible, but certainly not provable, suicide.
In 2009, Turing received a posthumous apology from the prime minister for this shabby treatment; in 2012, an extensive centenary celebration; and in 2013, an official pardon from the Queen.
Today, he is widely known as an intellectual warrior and has become something of a cult figure. Steve Jobs wanted his company鈥檚 bitten-apple logo to be associated with Turing鈥檚 love of apples. And in 2015, staff at the UK鈥檚 monitoring centre GCHQ queued out of their Cheltenham building to get an exclusive GCHQ copy of a new biography, Prof: Alan Turing decoded, by his nephew John Dermot Turing, who contributes a chapter in the guide.
Turing still lacks the final accolade of a statue in central London to complement that of his ultimate boss, Winston Churchill, who called the codebreakers 鈥済eese that laid the golden eggs 鈥� but never cackled鈥�. As the editors write pointedly in their preface: 鈥淚t is no overstatement鈥� without Turing, the war would probably have lasted longer, and might even have been won by the Nazis.鈥�
A handful of the guide鈥檚 33 contributors worked at Bletchley and knew Turing personally. Their reminiscences can be fascinating, funny, even moving. Captain Jerry Roberts, for example, was a graduate student of French and German who worked on Tunny, Adolf Hitler鈥檚 code for communicating with his top commanders that Turing broke using a technique nicknamed 鈥淭uringery鈥�. Roberts writes:鈥滻 have a strong mental image of him walking along the corridor in one of Bletchley Park鈥檚 Huts. With his gaze turned downwards, he was a shy and diffident man, flicking the wall with his fingers as he walked鈥� he was not a warrior king. But at that juncture, he was the most influential man in Europe bar none, and we owe our freedom to him.鈥�
Mathematician Peter Hilton worked on Tunny as an 18-year-old undergraduate. He recalls the priceless story of how Turing unexpectedly volunteered for the local Home Guard so he could become a first-class shot with a rifle. However, when filling in the standard application, Turing took the logical precaution of writing 鈥淣o鈥� against the question: 鈥淒o you understand that, by enrolling in His Majesty鈥檚 Local Defence Volunteers, you render yourself liable for military discipline?鈥�
When he failed to show up for parades and was court-martialled, the colonel asked him: 鈥淒o you realise this is a very serious offence?鈥� Turing calmly referred to his application. The colonel read it, then said, apoplectically: 鈥淵ou were improperly enrolled. Get out of my sight!鈥�
On the German side, such military rigidity often supplied valuable clues to the British codebreakers. For instance, the tendency of Tunny operators to repeat a message that had gone wrong in transmission, without changing the wheel settings on their encryption machine, offered the codebreakers two not-quite-identical messages for comparative analysis. They termed these 鈥渄epths鈥�, as Copeland explains in his chapter, 鈥淭unny: Hitler鈥檚 biggest fish鈥�.
鈥淭uring was the most influential man in Europe bar none, and we owe our freedom to him鈥�
Of the book鈥檚 42 chapters, Copeland contributes eight that he wrote alone and eight written with others. Bletchley veterans aside, most contributors are, like the editors, academics working in mathematics, computer science, cognitive science, artificial intelligence, philosophy 鈥� and biology. Including the latter specialism was just as well because Turing鈥檚 final work, his 1952 theory of morphogenesis, concerned the chemical basis for the evolution of patterns in nature, such as animal stripes, and the concept of artificial life.
There are, meanwhile, plenty of surprises. For example, a literature professor describes Turing鈥檚 interest in the paranormal, which led him to claim in 1950 that 鈥渢he statistical evidence, at least for telepathy, is overwhelming鈥�; and there is Turing the composer, responsible for some of the earliest computer music, recorded by the BBC in Turing鈥檚 Manchester labs.
Meaning of genius
Has anything significant been omitted from this authoritative collection? More reflection about Turing鈥檚 impact on gay rights might have been welcome. So would a separate chapter on the nature of his 鈥済enius鈥�, given that the term is applied to Turing by so many of the contributors. Indeed, Copeland and Bowen finish their engaging and informative introductory chapter by describing Turing as a 鈥渟hy, gay, witty, grumpy, courageous, unassuming and wildly successful genius鈥�. Very true 鈥� but which of these adjectives also apply to other geniuses in mathematics, physics and invention, and which are unique to Turing?
Considering my admiration for most of the guide, it may seem odd to recommend Turing newcomers to start with Hodges鈥檚 book. But it makes sense: his biography has little mathematics, and largely non-technical accounts of codebreaking. The Turing Guide, on the other hand, varies enormously, from the wholly biographical to the highly technical 鈥� with the latter particularly apparent when describing Turing鈥檚 contribution to mathematics and codebreaking. Graduate to it.
Once you do, you will find the whole Turing (or as much as we can ever know). Inevitably for a collection and with someone of such diverse achievements, and unconventional personality and personal life, there will be many voices and angles on the same aspects of Turing, and repetition.
But it is, I think, pretty much the last word on the subject. And it will ensure that while we may never decode the whole of Turing鈥檚 mind, his name will never again be forgotten.
This article appeared in print under the headline 鈥淎ll around Turing鈥�
