Alan Turing

Alan Turing & What Britain Lost

There are some people whose names become so closely associated with a subject that it is difficult to imagine the subject without them. Alan Turing is probably the clearest example in computing. Mention his name and most people will think of wartime codebreaking, Bletchley Park, the Enigma machine and perhaps the question of whether a machine can think.

All of those things belong in the story, but they can also make it surprisingly easy to miss the actual person.

Turing was not simply a wartime codebreaker who later became interested in computers. He was a mathematician whose interests moved between some remarkably different areas, and computing happened to be one of the places where his way of thinking proved particularly useful. He was interested in the limits of calculation, the nature of intelligence, mathematical biology and the practical problems involved in building machines that could carry out complicated operations. He could be intensely theoretical, but he was also quite happy to get his hands dirty with the practical details of making a machine work.

That combination turned out to be rather important.

Turing was born in London in 1912 and showed an early talent for mathematics and science. He went to Sherborne School and later King's College, Cambridge, where his mathematical ability became increasingly obvious. In 1936, while still only 24, he published the paper that introduced what became known as the Turing machine.

It is one of those pieces of mathematics that sounds rather dry when you describe it afterwards, but the basic idea was wonderfully simple. Turing wanted to understand what it actually meant for a problem to be computable. Rather than starting with a particular physical machine, he imagined an abstract device that could read and write symbols on an endless tape according to a set of rules. The machine itself was deliberately simple; what mattered was the question of what such a machine could, in principle, calculate.

That work became one of the foundations of theoretical computer science.

It is also worth remembering that Turing was doing this before there was anything resembling the modern computer industry. There were calculating machines, mechanical calculators and specialised devices, but the general-purpose electronic computers that would eventually transform the world did not yet exist. Turing was exploring the mathematics of computation at a time when the machine itself was still largely an idea.

Then the Second World War arrived, and the distinction between theoretical mathematics and practical computing became rather less clear.

Turing joined the Government Code and Cypher School and was sent to Bletchley Park, where British codebreakers were trying to understand German communications. The story is often simplified into “Turing broke Enigma”, but the real history was more complicated and, in some ways, more interesting. Polish cryptanalysts had already made crucial breakthroughs before the war, and British work at Bletchley built on those foundations. Turing became particularly important in attacking Naval Enigma and in developing the methods that allowed the Bombe machines to search through enormous numbers of possible settings.

The Bombe was not a computer in the modern sense. It was a specialised electromechanical machine designed for a very specific cryptanalytic task, and its usefulness depended on mathematical insight, careful procedures and information gathered from intercepted messages. Turing's contribution was therefore not simply that he designed a machine. He helped turn an enormously complicated cryptographic problem into something that could be attacked systematically.

The scale of the operation grew enormously during the war, and so did the importance of machinery. Turing also worked on other aspects of codebreaking, including statistical methods and techniques for dealing with German messages. By the end of the war, he had gained practical experience of something that would become increasingly important in the decades that followed: using machines to perform operations that would otherwise require an extraordinary amount of human calculation.

He had also spent several years working alongside people who were doing exactly the sort of thing that would later become known as computer science.

After the war, Turing's attention turned increasingly towards building actual computers. He joined the National Physical Laboratory and worked on the design of the Automatic Computing Engine, or ACE. His 1945 design was one of the earliest detailed designs for a stored-program computer, and it was far more ambitious than the machine that was eventually built.

There was a familiar problem, though. Designing a computer on paper and getting an institution to build the thing were two different matters.

The full ACE project moved slowly, while Turing became frustrated with the bureaucracy surrounding it. The smaller Pilot ACE eventually ran in 1950 and demonstrated that many of the ideas behind his design could work in practice. It was later developed into the DEUCE computer, which became a commercially produced machine.

Turing himself had moved on by then, joining the University of Manchester in 1948. Manchester was one of the most exciting places in Britain for the new field of computing, partly because the university had produced the Manchester Baby, the machine that demonstrated stored-program electronic computing in 1948. The Manchester Mark 1 followed, and Turing became involved in the development of software and programming methods for the machine.

This is another part of his story that tends to disappear behind the more famous wartime work. Turing wasn't simply interested in computers as pieces of engineering. He was interested in what you could actually do with them.

In 1950 he published a paper called Computing Machinery and Intelligence, which introduced the idea now widely associated with the Turing Test. The question he was trying to explore was whether a machine could think, although Turing recognised that arguing about the precise meaning of the word “think” could lead you into an endless philosophical swamp. His solution was to replace the question with something that could actually be tested: could a machine carry on a conversation well enough that a human could not reliably tell whether the other participant was a person or a machine?

The paper was decades ahead of the technology available to him. The computers of the early 1950s were enormous, expensive machines with tiny amounts of memory by modern standards. Nobody was going to have a casual conversation with one. Even so, Turing was already thinking about machine intelligence in a way that would become increasingly relevant as computing developed.

And he wasn't spending all his time thinking about machines.

One of the more surprising things about Turing's later work is how far he moved into mathematical biology. At Manchester he became fascinated by the way patterns form in living organisms, and in 1952 he published a paper on what he called the chemical basis of morphogenesis. He was interested in how relatively simple chemical processes could produce the complicated patterns found in nature, including things such as the arrangement of spots and stripes.

It is a very Turing sort of problem. Take something that looks enormously complicated and try to find the underlying rules that might produce it.

By this stage, though, his private life had become entangled with a legal system that treated homosexuality as a criminal offence.

In 1952, Turing reported a burglary at his Manchester home. During the investigation, he acknowledged that he had been in a relationship with another man. He was subsequently prosecuted for gross indecency, pleaded guilty and was given a choice between imprisonment and probation on the condition that he undergo hormonal treatment intended to suppress his libido.

He chose the probation.

The treatment involved oestrogen and had serious physical and psychological consequences. Turing was also stripped of his security clearance and could no longer work for GCHQ, which had succeeded the wartime codebreaking organisation. This was not simply a private humiliation. His professional life was affected because the British state had decided that his sexuality made him a security concern.

There is something particularly difficult about that decision when you look at what Turing had already done for the country. Hugh Alexander, one of the senior figures in wartime British cryptanalysis and later head of cryptanalysis at GCHQ, was officially approved to appear as a character witness during Turing's prosecution. He regarded Turing as a national asset.

The state knew perfectly well what sort of scientist it was dealing with.

And yet, only a few years after the war, that same state subjected him to criminal prosecution and removed his ability to continue working in an area where his expertise was highly valuable.

Turing continued working after the prosecution. He was still producing important mathematical research, and there is no evidence that his curiosity or ability simply disappeared. His work on morphogenesis was developing, and he remained interested in computing and the question of machine intelligence.

But the circumstances around him had changed considerably. The treatment he had been forced to undergo had affected him physically, his work with government security organisations had ended, and the country in which he had played such an important wartime role had made it clear that there were parts of his life for which he could be punished.

On 8 June 1954, Turing was found dead at his home in Wilmslow. The official cause was cyanide poisoning and his death was recorded as suicide. A half-eaten apple was found beside his bed, which has led to the familiar story that he deliberately poisoned an apple, although the apple was never tested and there was no suicide note. Turing's mother, Ethel, never accepted that he had deliberately killed himself and believed that his death could have been accidental.

He was 41 years old.

It is tempting to turn the ending into a neat story about a brilliant man being destroyed by an intolerant society, but the reality is more complicated than any single explanation can capture. We cannot know exactly what Turing was thinking in the final months of his life, or what part the prosecution, the hormonal treatment, the loss of his security clearance and everything else played in his death. What we do know is that Britain had treated one of its most gifted scientists as a criminal because he was gay, subjected him to a degrading medical punishment and prevented him from continuing work for the organisation with which he had helped build the foundations of British signals intelligence.

His death also came at a particularly interesting point in the development of computing.

The machines Turing had been thinking about in the 1940s were beginning to become practical systems. Universities and research organisations were building computers, companies were beginning to see commercial possibilities, and programming was slowly emerging as a discipline in its own right. Turing had already spent years thinking about what these machines could become, rather than merely what they could calculate at that particular moment.

Nobody can say with any certainty what he would have done with the next twenty years. It would be wrong to turn him into a kind of mythical figure who was supposedly destined to invent every important idea in computing. Scientists have false starts, change direction, become fascinated by subjects that lead nowhere and sometimes spend years pursuing questions that other people eventually abandon.

But Turing was only 41, and he was working across several areas that would become enormously important. He had contributed to the mathematical foundations of computing, helped develop practical methods for using machines in cryptanalysis, worked on early stored-program computers, thought seriously about machine intelligence and was producing original research into mathematical biology.

That makes the loss difficult to measure.

Britain did eventually become an important centre of computer research and manufacturing, but the country's early computer industry faced plenty of problems, from limited investment to competition from much larger American companies. Turing cannot simply be inserted into that history as the missing person who would somehow have fixed all of it. There is no evidence for that, and history doesn't give us the luxury of running the experiment.

What we can say is that an exceptionally capable scientist was removed from the British computing scene at precisely the point when it was beginning to develop into something much larger than the experimental world he had known during the war.

The official response to what had happened took a very long time. Gordon Brown formally apologised on behalf of the British government in 2009 for the way Turing had been treated. In 2013, Queen Elizabeth II granted him a posthumous pardon for the conviction, and the 2017 legislation commonly known as the Alan Turing Law extended posthumous pardons to other men convicted under historical laws relating to homosexual activity, while also providing a process for living people to seek disregards of certain convictions.

By then, Turing had become one of the most recognisable names in computing.

There is a certain irony in that. The man who spent so much of his life thinking about whether machines could imitate human intelligence has himself become a kind of shorthand: Bletchley Park, Enigma, computers, artificial intelligence. Those associations are deserved, but they can make his life seem much tidier than it actually was.

Turing's story was not simply one of a wartime genius who went on to invent the computer and then met a tragic end. He was part mathematician, part engineer, part cryptanalyst and, increasingly, something that did not yet have a proper name: a computer scientist. He moved comfortably between abstract mathematics and practical machinery, and he was interested in questions that were only beginning to become possible to ask because electronic computers existed at all.

Perhaps the most frustrating part is that we have no way of knowing what he would have made of the next stage.

By the time he died, the machines were finally beginning to catch up with some of the ideas he had been thinking about for years. He had already spent much of his career looking beyond what computers could do and asking what they might eventually become.

He never got the chance to find out.