Alan Turing’s Memoir

Alan Turing lived a life shrouded in secrecy. His work on the German Enigma code, which Winston Churchill called “the greatest single contribution to the war effort,” remained under the Official Secrets Act long after his death. For a long time, his homosexuality caused his role as the Father of Computer Science to be greatly downplayed. In spite of all of this, his is known today as one of the most famous cryptographers in history, a position that is more than earned by his accomplishments.

Alan Turing was born June 23rd, 1912. When he was only a year old his mother, in order to join his father in India, left him and his older brother with a retired army colonel and his wife. Turing went to a public boarding school. It was there that his scientific curiosity and romantic nature began to take form, His unsupervised chemical experiments, unconventional approach to mathematics, and poor grades in English prompted the headmaster to write, in a letter to his parents, “If he is to stay in Public School, he must aim at becoming educated. If he is to be solely a Scientific Specialist, he is wasting his time at Public School.” His schooling wasn’t completely to waste, however, as he fell into unrequited love with a student a few forms above him, Christopher Morcom. They became friends and briefly collaborated on science experiments, but their relationship came to an end when Morcom died suddenly in February 1930.

Despite his mediocre grades, Turing won a mathematics scholarship to King’s College, Cambridge. His career at King’s was much more successful than at boarding school. In 1935, at the age of 22, he was elected a fellow at King’s because of a dissertation in which he proved the central limit theorem, despite the fact that it had already been proven in 1922 by Jarl Lindeberg. In 1936, Turing left England for Princeton University, where he made his first great contribution to computer science.

One of the greatest challenges of mathematics of the day was the Entscheidungsproblem. The Entscheidungsproblem, in brief, is the question of whether there is a definite method which can be applied to a preposition to decided whether a preposition is provable. The main problem was that the question, which to be answered required a concrete definition of method, contained elements of both philosophy and mathematics.

In late 1936, Turing published his paper “On computable numbers, with an application to the Entscheidungsproblem.” This paper proved momentous not for mathematics, but for computer science. First, Turing replaced the arithmetic base of the Entscheidungsproblem and the various proposed solutions to it with simple, hypothetical devices that later became known as Turing machines. He established that these machines would be capable of performing any mathematical computation so long as it was in an algorithm. Then he went on to prove that there was no solution to the Entscheidungsproblem because it is not possible to decide algorithmically whether a Turing machine will ever halt. In one fell swoop, Turing had established the mechanical computability of everything computable and created the concept of the modern computer.

Turing, upon his return to Cambridge in 1938, began working part-time with the Government Code and Cypher School (GC&CS). He was especially interested in the German code Enigma. Poland had developed Bomba, which could decrypt Enigma, but relied on an indicator procedure that Germans were likely to change, as they did in May 1940. Turing sought a less insecure procedure. and he had produced a theoretical specification of the “bombe” even before arriving at Bletchley Park in 1939.

The bombe was a machine that worked out which sockets of the Enigma machine were connected to which other sockets on the day in question and what the wheel order inside the machine was. Turing could not design a machine that did this directly, since there were too many potential configurations of the sockets and wheels. Instead he designed the bombe so that, through a series of logical deductions, it ruled out as many of the plugboard socket connections and wheel orders as possible, leaving only a few to try to discover manually. If one of these deduction was impossible, the bombe would go on to test another set of assumptions, and then another, and so on, until it found a set of assumptions that didn’t produce impossible results. These possible assumptions were relatively few, so the cryptographers would try those out manually on a replica of Enigma to see which one was correct.

The first bombe, installed at Bletchley Park on March 18th, 1940, was a failure. The bombe, powerful in theory, only worked in practice if cryptographers identified words, or “cribs,” that the bombe could then use to break the code. Turing’s original machine required much longer cribs than those that the cryptographers could figure out. The answer to this problem came from fellow code-breaker Gordon Welchman. Welchman realized that Turing’s original bombe only made one deduction based on the given scenario before moving onto the next. Thus, the bombe could easily get on the wrong track and then start the series of deductions over. Welchman proposed that the bombe could be adapted so that it took other possibilities into account, eliminating the need to start from scratch every time it hit a dead end. Though Turing was initially skeptical of the changes, he quickly accepted the alterations. He also added an alteration of his own: “simultaneous scanning.” The original bombe required that the cryptographers test one assumed plugboard socket at a time. Simultaneous scanning allowed the cryptographers to see if a plug was connected to any other socket. Armed with these alterations, the next attempt at creating a bombe was successful.

Despite being Bletchley Park’s most successful code-breaker and head of Hut 8, Turing was not popular among his fellows. He had a reputation for being eccentric, and some have suggested that he would have been diagnosed with Asperger’s had he been examined today. His only interest in researching the Naval Enigma code, in his own words, was “because no one else was doing anything about it and I could have it to myself.” He would run long-distance for up to 40 miles because it “gave [him] time to think” and rode to work on a broken bicycle while wearing a gas mask. His tea mug he chained to a radiator with a padlock. As for his personality, he was a loner who would refuse to meet anyone’s eyes and would scurry away from anyone who tried to strike up a conversation, especially women. He once told one of his colleagues that he hated spending time with women because “they just open their mouths and say things which are so banal, it’s as if a frog had popped out.”

The only significant relationship he ever had with a woman was in 1941, when he became engaged to Joan Clarke, one of the cleverest cryptographers in Bletchley Park and his good friend. He called off the engagement a few months later, shortly after telling Clarke that he was homosexual. She and he remained close friends for the rest of his life.

Turing travelled to the U.S. in 1942 to help their cryptographers with the construction of their bombe. He was not impressed by the American bombe design. During his time in America, he also assisted Bell Laboratories in creating a secure speech device. He returned to Bletchley Park in March 1943 and gave up his position as head of Hut 8, instead becoming a general consultant for cryptanalysis. By mid-1943, Turing had stopped working on the Enigma problem. Hugh Alexander, Turing’s successor as head of Hut 8, said that “if anyone was indispensable to Hut 8 it was Turing.”

From 1945 to 1947, Turing worked on the ACE (Automatic Computing Engine), one of the first computers in a modern sense. It was his work on this computer that inspired his 1950 paper “Computer Machinery and Intelligence,” which can be safely said to be one of the most influential scientific papers of the 20th century. In this paper, Turing replaces the classical question of whether machines can think with the question of whether a computer could ever “do well in the imitation game.”

What he proposed later became known as the Turing test and is the cornerstone on which artificial intelligence is based. There are three players: A, B, and C. A is a human being, and B is a computer. Through a series of written questions and answers, C tries to ascertain which of the other two players is the machine. Again, Turing was far ahead of his time, this time in the development of artificial intelligence and in questioning what it means to be “human.”

Unfortunately, Turing’s accomplishments in cryptography and computer science would not be given the attention they were due for a long time. In 1952, Turing’s house was burgled, and he unwisely told the police that he was in a homosexual relationship with a friend of the man that had done the thieving. He was prosecuted for indecent behavior and, in spite of his 1945 Order of the British Empire and a character statement from Hugh Alexander, was given a horrible choice. He had to either go to prison for three to five years or be injected with estrogen, a supposed cure for his homosexuality. He chose the estrogen. Over the course of his treatment, Turing had trouble concentrating, felt weak, and developed breasts like a woman. In spite of all this, his family and friends found him enthusiastic about his research. His estrogen treatment ended a year later.

In 1954, two years after his trial, Alan Turing was found dead in his rooms by his housekeeper. A half-eaten apple, laced with cyanide, was found beside him. The coroner ruled the death as suicide, but in recent years that ruling has been thrown into doubt because of Turing’s apparently good mental health at the time of his death. Some experts believe that the death may have been an accident or even an assassination by the paranoid Cold War government.

We may never know what really caused the death of Alan Turing, but his influence on history is clear. Through his role in breaking Enigma, Turing shortened World War II by two to five years, and his papers on artificial intelligence and mechanical computing formed the foundation of modern computer science. Even the word processing program that I am using to type out this paper owes itself to Turing’s genius. No matter what your opinion on homosexuality is, there is no doubt that Alan Turing is one of the most influential and important figures of the 20th century.