Part 1 of Turing: a natural philosopher (1997)
IntroductionAlan Turing dared to ask whether a machine could think. His contributions to understanding and answering this and other questions defy conventional classification. At the close of the twentieth century, the 1936 concept of the Turing machine appears not only in mathematics and computer science, but in cognitive science and theoretical biology. His 1950 paper 'Computing machinery and intelligence,' describing the so-called Turing test, is a cornerstone of the theory of artificial intelligence. In between, Turing played a vital role in the outcome of the Second World War, and produced single-handedly a far-sighted plan for the construction and use of an electronic computer. He thought and lived a generation ahead of his time, and yet the features of his thought that burst the boundaries of the 1940s are better described by the antique words: natural philosophy.
Alan Turing's immersion in and attack upon Nature was a unity; divisions between mathematics, science, technology and philosophy in his work have tended to obscure his ideas. He was not a prolific author; much remained unpublished in his lifetime; some remained secret into the 1990s. Private communications shed a little more light on the development of his thought, a subject on which he was generally silent. We shall see, for instance, how he came to logic and computation from a youthful fascination with the physical description of mind. But we have only hints as to the formation of his convictions amidst the secrecy of wartime cryptanalysis, and suggestions of fresh ideas are lost in the drama of his mysterious death.
The Nature of Turing's WorldAlan Mathison Turing was born in London on 23 June 1912, and from the beginning showed a personality out of place in the upper-middle-class schooling undergone by sons of Indian Civil Service officers. Conformity to class meant unquestioning obedience to the rituals of the British preparatory and public school. But the book Natural Wonders Every Child Should Know opened his eyes to the concept of scientific explanation, and from then on Nature as opposed to human convention commanded his attention, as many nagging reports demonstrated. Duty, hierarchy, masters, servants, rules and games would later play a striking role in the illustration of his ideas; but while at school he was more baffled and incompetent than rebellious at the demands of the British empire, ignoring as much as possible while pursuing his own priorities. In 1925 he wrote to his mother : 'I am making a collection of experiments in the order I want to do them in. I always want to make things from the thing that is commonest in nature and with the least waste of energy.'
His experimental chemistry incurred displeasure, as did poor handwriting and unconventional methods in his mathematics. He was bottom of the form in English. The headmaster wrote, 'If he is to stay at a Public School, he must aim at becoming educated. If he is to be solely a Scientific Specialist, he is wasting his time at a Public School' and this judgment on British ruling-class priorities was almost correct. Turing was nearly prevented from taking the equivalent of GCSEs. Thereafter, he found his level in Einstein's own exposition of Relativity and Eddington's view of quantum mechanics in The Nature of the Physical World. But this was isolated private study, and he might never have felt the urge to communicate but for an impossibly romantic story.
Human nature brought him to life; but it was his own homosexual nature, bringing revelation and trauma in equal measure. He fell in unrequited love with Christopher Morcom, a very talented youth in the school sixth form, and his longing for friendship brought him to communicate. A brief flowering of scientific collaboration perished when Morcom suddenly died in February 1930. Turing's correspondence with the dead boy's mother gives insight into the development of his ideas in the aftermath. He was concerned to believe the dead boy could still exist in spirit, and to reconcile such a belief with science. To this end he wrote for Mrs Morcom an essay, probably in 1932. It is the private writing of a twenty-year-old, and must be read as testament to background and not as a thesis upheld in public; nevertheless it is a key to Turing's future development. 
In stating the classic paradox of physical determinism and freewill, Turing is influenced by Eddington's assertion that quantum mechanical physics ('more modern science') yields room for human will. Eddington asked how could 'this collection of ordinary atoms be a thinking machine?' and Turing tries to find some answer. His essay goes on to espouse belief in a spirit unconstrained by the body: 'when the body dies the 'mechanism' of the body, holding the spirit is gone and the spirit finds a new body sooner or later perhaps immediately.' Letters show he retained such ideas at least until 1933.
Turing was much more successful in undergraduate work than at school, and King's College lent him a protective ambience sympathetic to homosexuality and unconventional opinion. He was not, however, one of its élite social circle, nor in a political group. Politically, he responded briefly to the 1933 Anti-War movement, but not to the Communist party as others of his close acquaintance did. Nor did Turing share the pacifism of his first lover, fellow mathematics student James Atkins.
In a similar way Turing found a home in Cambridge mathematical culture, yet did not belong entirely to it. The division between 'pure' and 'applied' mathematics was at Cambridge then as now very strong, but Turing ignored it, and he never showed mathematical parochialism. If anything, it was the attitude of a Russell that he acquired, assuming that mastery of so difficult a subject granted the right to invade others. Turing showed little intellectual diffidence once in his stride: in March 1933 he acquired Russell's Introduction to Mathematical Philosophy, and on 1 December 1933, the philosopher R. B. Braithwaite minuted in the Moral Science Club records: 'A. M. Turing read a paper on 'Mathematics and logic.' He suggested that a purely logistic view of mathematics was inadequate; and that mathematical propositions possessed a variety of interpretations, of which the logistic was merely one.' At the same time he was studying von Neumann's 1932 Grundlagen den Quantenmechanik. Thus, it may be that Eddington's claims for quantum mechanics had encouraged the shift of Turing's interest towards logical foundations. And it was logic that made Alan Turing's name.
© 1997, Andrew Hodges.