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Andrew Hodges teaches mathematics at Wadham College, University of Oxford. A colleague of Roger Penrose, he is also an active contributor to the mathematics of fundamental physics.

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"One of the finest scientific biographies I've ever read: authoritative, superbly researched, deeply sympathetic, and beautifully told."--Sylvia Nasar, author ofA Beautiful Mind

"A captivating, compassionate portrait of a first-rate scientist who gave so much to a world that in the end cruelly rejected him. Perceptive and absorbing, Andrew Hodges's book is scientific biography at its best."--Paul Hoffman, author of The Man Who Loved Only Numbers

"A remarkable and admirable biography."--Simon Singh, author of The Code Book and Fermat's Enigma

"A first-rate presentation of the life of a first-rate scientific mind.... It is hard to imagine a more thoughtful and compassionate portrait of a human being."--from the Foreword by Douglas Hofstadter

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Alan Turing: The Enigma

PRINCETON UNIVERSITY PRESS

Contents

List of Plates..............................................ixForeword by Douglas Hofstadter..............................xiPreface to the 2012 Centenary edition.......................xv1 Esprit de Corps to 13 February 1930.......................12 The Spirit of Truth to 14 April 1936......................463 New Men to 3 September 1939...............................1114 The Relay Race to 10 November 1942........................160BRIDGE PASSAGE to 1 April 1943..............................2425 Running Up to 2 September 1945............................2596 Mercury Delayed to 2 October 1948.........................3147 The Greenwood Tree to 7 February 1952.....................3908 On the Beach to 7 June 1954...............................456Postscript..................................................529Author's Note...............................................530Notes.......................................................541Acknowledgements............................................569Index.......................................................570

Chapter One

Beginning my studies the first step pleas'd me so much, The mere fact consciousness, these forms, the power of motion, The least insect or animal, the senses, eyesight, love, The first step I say awed me and pleas'd me so much, I have hardly gone and hardly wish'd to go any farther, But stop and loiter all the time to sing it in ecstatic songs.

A son of the British Empire, Alan Turing's social origins lay just on the borderline between the landed gentry and the commercial classes. As merchants, soldiers and clergymen, his ancestors had been gentlemen, but not of the settled kind. Many of them had made their way through the expansion of British interests throughout the world.

The Turings could be traced back to Turins of Foveran, Aberdeenshire, in the fourteenth century. There was a baronetcy in the family, created in about 1638 for a John Turing, who left Scotland for England. Audentes Fortuna Juvat (Fortune Helps the Daring) was the motto of the Turings, but however brave, they were never very lucky. Sir John Turing backed the losing side in the English civil war, while Foveran was sacked by the Covenanters. Denied compensation after the Restoration, the Turings languished in obscurity during the eighteenth century, as the family history, the Lay of the Turings, was to describe:

    Walter, and James and John have known,
    Not the vain honours of a crown,
    But calm and peaceful life –
    Life, brightened by the hallowing store
    Derived from pure religion's lore!
    And thus their quiet days passed by;
    And Foveran's honours dormant lie,
    Tilt good Sir Robert pleads his claim
    To give once more the line to fame:
    Banff's castled towers ring loud and high
    To kindly hospitality
    And thronging friends around his board
    Rejoice in TURING'S line restored!

Sir Robert Turing brought back a fortune from India in 1792 and revived the title. But he, and all the senior branches of the family, died off without male heirs, and by 1911 there were but three small clusters of Turings in the world. The baronetcy was held by the 84-year-old eighth baronet, who had been British Consul in Rotterdam. Then there was his brother, and his descendants, who formed a Dutch branch of Turings. The junior branch consisted of the descendants of their cousin, John Robert Turing, who was Alan's grandfather.

John Robert Turing took a degree in mathematics at Trinity College, Cambridge, in 1848, and was placed eleventh in rank, but abandoned mathematics for ordination and a Cambridge curacy. In 1861 he married nineteen year old Fanny Boyd and left Cambridge for a living in Nottinghamshire, where he fathered ten children. Two died in infancy and the surviving four girls and four boys were brought up in a regime of respectable poverty on a clerical stipend. Soon after the birth of his youngest son, John Robert suffered a stroke and resigned his living. He died in 1883.

As his widow was an invalid, the care of the family fell upon the eldest sister Jean, who ruled with a rod of iron. The family had moved to Bedford to take advantage of its grammar school, where the two elder boys were educated. Jean started her own school, and two of the other sisters went out as schoolteachers, and generally sacrificed themselves for the sake of advancing the boys. The eldest son, Arthur, was another Turing whom fortune did not help: he was commissioned in the Indian Army, but was ambushed and killed on the North-West Frontier in 1899. The third son Harvey emigrated to Canada, and took up engineering, though he was to return for the First World War and then turn to genteel journalism, becoming editor of the Salmon and Trout Magazine and fishing editor of The Field. The fourth son Alick became a solicitor. Of the daughters only Jean was to marry: her husband was Sir Herbert Trustram Eve, a Bedford estate agent who became the foremost rating surveyor of his day. The formidable Lady Eve, Alan's Aunt Jean, became a moving spirit of the London County Council Parks Committee. Of the three unmarried aunts, kindly Sybil became a Deaconess and took the Gospel to the obstinate subjects of the Raj. And true to this Victorian story, Alan's grandmother Fanny Turing succumbed to consumption in 1902.

Julius Mathison Turing, Alan's father, was the second son, born on 9 November 1873. Devoid of his father's mathematical ability, he was an able student of literature and history, and won a scholarship to Corpus Christi College, Oxford, from where he graduated with a BA in 1894. He never forgot his early life of enforced economy, and typically never paid the 'farcical' three guineas to convert the BA into an MA. But he never spoke of the miseries of his childhood, too proud to moan of what he had left behind and risen above, for his life as a young man was a model of success. He entered for the Indian Civil Service, which had been thrown open to entry by competitive examination in the great-liberal reform of 1853, and which enjoyed a reputation surpassing even that of the Foreign Office. He was placed seventh out of 154 in the open examination of August 1895. His studies of the various branches of Indian law, the Tamil language and the history of British India then won him seventh place again in the Final ICS examination of 1896.

He was posted to the administration of the Presidency of Madras, which included most of southern India, reporting for duty on 7 December 1896, the senior in rank of seven new recruits to that province. British India had changed since Sir Robert left it in 1792. Fortune no longer helped the daring; fortune awaited the civil servant who could endure the climate for forty years. And while (as a contemporary writer put it) the district officer was 'glad of every opportunity to cultivate intercourse with the natives,' the Victorian reforms had ensured that 'the doubtful alliances which in old days assisted our countrymen to learn the languages' were 'no longer tolerated by morality and society.' The Empire had become respectable.

With the help of a £100...