Turing was born in London in 1912. In 1936, at Cambridge, he wrote "On Computable Numbers," defining "computable" through an imaginary Turing machine — and, in passing, proving Hilbert's "decision problem" (Entscheidungsproblem) unsolvable. That was the year the modern computer was born, mathematically. When war came, he entered Bletchley Park to lead the breaking of Germany's Enigma cipher, designing the electromechanical "Bombe" — by some estimates shortening the war by more than two years. After the war he worked on early computers in Manchester, proposed the Turing Test in 1950 (founding artificial intelligence), and in 1952 published his theory of morphogenesis, explaining why living things grow their patterns. That same year he was convicted of "gross indecency" for a homosexual relationship and subjected to chemical castration. On 7 June 1954 he died of cyanide poisoning, aged just 41.
1935–1936: deciding to take "computation" apart to the bottom. In a Cambridge lecture, Max Newman raised Hilbert's decision problem: is there a mechanical procedure that can decide the truth of any mathematical statement? Most people would hunt for a clever algorithm; Turing asked one level deeper — what is a "mechanical procedure"? His answer was startlingly plain: an infinite paper tape, a read/write head, a table of rules. He proved this crude "Turing machine" could simulate any algorithm, and could be built into a universal machine (one that reads in the description of another machine and runs it) — the very prototype of today's stored-program computer. Princeton's Church reached an equivalent result almost simultaneously via the λ-calculus, but Turing won out because his model was as intuitive as "a person following rules on paper" — anyone could grasp it.
1939–1940: deciding to mechanize the codebreaking. Enigma reset its settings daily; brute force by hand was hopeless. Polish mathematicians had already built the electromechanical bomba before the war to break an earlier Enigma; when Turing took over he rebuilt the whole approach — relying not on German operators' habits but on known plaintext fragments (cribs, like the wetter, "weather," almost every message carried). His Bombe tested tens of thousands of rotor combinations at once, using logical contradiction to eliminate wrong settings automatically, and he devised the Banburismus statistical method for the hardest, naval Enigma. In October 1941, short of staff, he and three colleagues bypassed the bureaucracy and wrote directly to Churchill; Churchill scrawled "Action This Day," and the resources arrived that day.
Sources: Andrew Hodges, Alan Turing: The Enigma (1983), Ch. 3–5; Turing, "On Computable Numbers," Proc. London Math. Soc. (1936).Before Turing became "Turing," there was a person named Christopher Morcom. A schoolmate at Sherborne, a year older, bright and open, he was the one close friend of Turing's youth — and almost certainly his first love. Turing later said many of his own achievements were driven by a wish to "be worthy of" him.
In February 1930, Christopher suddenly died of bovine tuberculosis contracted in childhood. Turing was shattered. He wrote letter after letter to Christopher's mother, circling one question: can the mind exist apart from the body? He first leaned toward believing the soul survives, but as his thinking deepened he turned to a thoroughgoing materialism — if the mind is only a certain organization of matter, then in principle it could be re-realized in other matter (a machine). The earth-shaking question twenty years later, "Can machines think?", has its source in this boyhood loss: grief pushed him not toward religion but toward a lifelong project of mechanizing the mind.
Sources: Andrew Hodges, Alan Turing: The Enigma (1983), Ch. 1–2; Turing's letters to Mrs Morcom.He padlocked his tea mug to the radiator pipe. Mugs kept vanishing at Bletchley Park; too bothered to play the social game, Turing simply locked his up — an extremely practical, slightly childlike fix that became a favorite anecdote among colleagues.
In pollen season he cycled to work in a gas mask. With severe hay fever, rather than take medicine he would ride miles in a military gas mask, indifferent to the stares — he always attacked a problem at the physical level rather than bending to convention.
He was a near-Olympic-class long-distance runner. In 1947 he ran a marathon in 2 hours 46 minutes and was briefly in consideration for the 1948 British Olympic trials (an injury ended it). He often simply ran the tens of miles to a meeting in London, arriving while colleagues were still waiting for trains.
His bicycle chain slipped off every fixed number of revolutions — and he didn't fix it, he counted. Timing the revolutions, he would stop and reseat the chain just before it fell, then ride on: using an "algorithm" to route around a mechanical fault that a screwdriver should have solved is almost a metaphor for how he thought.
He was almost defenselessly candid. Blunt, often stammering, with a distinctive laugh; he rarely calculated the social games of others and was poor at concealing himself — a transparency that was his charm and, later, his fatal weakness.
Sources: Andrew Hodges, Alan Turing: The Enigma (1983), Ch. 4–6; memoirs of Bletchley Park colleagues.First, "Turing broke Enigma alone" is a myth that erases many people. The first to actually break Enigma were Polish mathematicians, Marian Rejewski and others — who reconstructed Enigma's internal wiring before the war, built the bomba, and in 1939 handed their results to Britain and France. At its peak Bletchley Park had nearly ten thousand people (largely women operators) collaborating. Turing was a crucial link, but crediting the victory to one man betrays exactly the collective he depended on.
Second, he was a dazzling designer but a poor finisher. After the war at the National Physical Laboratory (NPL), Turing produced a far-sighted design for the ACE computer — but, too far ahead and impatient with engineering compromise and bureaucracy, he clashed repeatedly with management and left in frustration; the machine was heavily simplified and delayed for years. Many of his ideas were ahead of their time, yet in the end others had to realize them for him.
Third, the "poisoned apple martyrdom" story may be told too cleanly. In 1952, convicted of "gross indecency" over his relationship with Arnold Murray, he chose estrogen injections (chemical castration) over prison — damaging body and mind — and lost his security clearance. In 1954 he died of cyanide poisoning, a half-eaten apple by his bed (never tested for cyanide), with an inquest verdict of suicide. But historian Jack Copeland notes he was then doing electroplating experiments, handled cyanide constantly, showed no obvious change before death, and his mother firmly believed it was an accident — flattening his death into "Snow White biting the poisoned apple" is later romantic embellishment that obscures the more real man.
Sources: Andrew Hodges, Alan Turing: The Enigma (1983), Ch. 7–8; B. Jack Copeland, Turing: Pioneer of the Information Age (2012).Turing's lesson for the "AI super-individual" lies in the level of abstraction at which he solved problems. While everyone hunted for a "smarter algorithm," he asked one level down — what is a "mechanical procedure"? That single act of taking the problem down to the level of definition conjured the entire theory of computation from nothing: the real leverage often lies not in solving the existing problem faster, but in redefining the frame the problem sits in. But the same gift has a flip side — being absorbed in thinking things through is not the same as getting the world to use them, which is exactly why he failed at the NPL. So what to take from him is a tension: the nerve to drop a problem to its lowest level and reinvent it, paired with the patience to land a brilliant idea and make it usable to others. As for his being crushed by his era, that is another warning bell: a person's worth must never be judged by the sex of the person they love.