If all Alan Turing had done was answer, in the negative, a
vexing question in the arcane realm of mathematical logic, few
nonspecialists today would have any reason to remember him. But
the method Turing used to show that certain propositions in a
closed logical system cannot be proved within that system--a
corollary to the proof that made Kurt Godel famous--had enormous
consequences in the world at large. For what this eccentric
young Cambridge don did was to dream up an imaginary machine--a
fairly simple typewriter-like contraption capable somehow of
scanning, or reading, instructions encoded on a tape of
theoretically infinite length. As the scanner moved from one
square of the tape to the next--responding to the sequential
commands and modifying its mechanical response if so
ordered--the output of such a process, Turing demonstrated,
could replicate logical human thought.

The device in this inspired mind-experiment quickly acquired a
name: the Turing machine. And so did another of Turing's
insights. Since the instructions on the tape governed the
behavior of the machine, by changing those instructions, one
could induce the machine to perform the functions of all such
machines. In other words, depending on the tape it scanned, the
same machine could calculate numbers or play chess or do
anything else of a comparable nature. Hence his device acquired
a new and even grander name: the Universal Turing Machine.

Does this concept--a fairly rudimentary assemblage of hardware
performing prodigious and multifaceted tasks according to the
dictates of the instructions fed to it--sound familiar? It
certainly didn't in 1937, when Turing's seminal paper, "On
Computable Numbers, with an Application to the
Entscheidungsproblem," appeared in Proceedings of the London
Mathematical Society. Turing's thoughts were recognized by the
few readers capable of understanding them as theoretically
interesting, even provocative. But no one recognized that
Turing's machine provided a blueprint for what would eventually
become the electronic digital computer.

So many ideas and technological advances converged to create the
modern computer that it is foolhardy to give one person the
credit for inventing it. But the fact remains that everyone who
taps at a keyboard, opening a spreadsheet or a word-processing
program, is working on an incarnation of a Turing machine.

Turing's 1937 paper changed the direction of his life and
embroiled a shy and vulnerable man ever more directly in the
affairs of the world outside, ultimately with tragic consequences.

Alan Mathison Turing was born in London in 1912, the second of
his parents' two sons. His father was a member of the British
civil service in India, an environment that his mother considered
unsuitable for her boys. So John and Alan Turing spent their
childhood in foster households in England, separated from their
parents except for occasional visits back home. Alan's loneliness
during this period may have inspired his lifelong interest in the
operations of the human mind, how it can create a world when the
world it is given proves barren or unsatisfactory.

At 13 he enrolled at the Sherbourne School in Dorset and there
showed a flair for mathematics, even if his papers were
criticized for being "dirty," i.e., messy. Turing recognized his
homosexuality while at Sherbourne and fell in love, albeit
undeclared, with another boy at the school, who suddenly died of
bovine tuberculosis. This loss shattered Turing's religious
faith and led him into atheism and the conviction that all
phenomena must have materialistic explanations. There was no
soul in the machine nor any mind behind a brain. But how, then,
did thought and consciousness arise?

After twice failing to win a fellowship at the University of
Cambridge's Trinity College, a lodestar at the time for
mathematicians from around the world, Turing received a
fellowship from King's College, Cambridge. King's, under the
guidance of such luminaries as John Maynard Keynes and E.M.
Forster, provided a remarkably free and tolerant environment for
Turing, who thrived there even though he was not considered quite
elegant enough to be initiated into King's inner circles. When he
completed his degree requirements, Turing was invited to remain
at King's as a tutor. And there he might happily have stayed,
pottering about with problems in mathematical logic, had not his
invention of the Turing machine and World War II intervened.

Turing, on the basis of his published work, was recruited to
serve in the Government Code and Cypher School, located in a
Victorian mansion called Bletchley Park in Buckinghamshire. The
task of all those so assembled--mathematicians, chess champions,
Egyptologists, whoever might have something to contribute about
the possible permutations of formal systems--was to break the
Enigma codes used by the Nazis in communications between
headquarters and troops. Because of secrecy restrictions,
Turing's role in this enterprise was not acknowledged until long
after his death. And like the invention of the computer, the
work done by the Bletchley Park crew was very much a team
effort. But it is now known that Turing played a crucial role in
designing a primitive, computer-like machine that could decipher
at high speed Nazi codes to U-boats in the North Atlantic. 

After the war, Turing returned to Cambridge, hoping to pick up
the quiet academic life he had intended. But the newly created
mathematics division of the British National Physical Laboratory
offered him the opportunity to create an actual Turing machine,
the ACE or Automatic Computing Engine, and Turing accepted. What
he discovered, unfortunately, was that the emergency spirit that
had short-circuited so many problems at Bletchley Park during
the war had dissipated. Bureaucracy, red tape and interminable
delays once again were the order of the day. Finding most of his
suggestions dismissed, ignored or overruled, Turing eventually
left the NPL for another stay at Cambridge and then accepted an
offer from the University of Manchester where another computer
was being constructed along the lines he had suggested back in
1937.

Since his original paper, Turing had considerably broadened his
thoughts on thinking machines. He now proposed the idea that a
machine could learn from and thus modify its own instructions. In
a famous 1950 article in the British philosophical journal Mind,
Turing proposed what he called an "imitation test," later called
the "Turing test." Imagine an interrogator in a closed room
hooked up in some manner with two subjects, one human and the
other a computer. If the questioner cannot determine by the
responses to queries posed to them which is the human and which
the computer, then the computer can be said to be "thinking" as
well as the human.

Turing remains a hero to proponents of artificial intelligence in
part because of his blithe assumption of a rosy future: "One day
ladies will take their computers for walks in the park and tell
each other, 'My little computer said such a funny thing this
morning!'"

Unfortunately, reality caught up with Turing well before his
vision would, if ever, be realized. In Manchester, he told
police investigating a robbery at his house that he was having
"an affair" with a man who was probably known to the burglar.
Always frank about his sexual orientation, Turing this time got
himself into real trouble. Homosexual relations were still a
felony in Britain, and Turing was tried and convicted of "gross
indecency" in 1952. He was spared prison but subjected to
injections of female hormones intended to dampen his lust. "I'm
growing breasts!" Turing told a friend. On June 7, 1954, he
committed suicide by eating an apple laced with cyanide. He was
41.   

TIME senior writer Paul Gray writes on a Turing machine


BORN June 23, 1912, in London
1931-5 Studies mathematical logic at Cambridge
1937 Landmark paper introduces the imaginary Turing machine
1939-45 Secret work with team breaking the Nazis' Enigma codes
1950 Paper in journal Mind predicts the advent of artificial
intelligence
1952 Convicted of "gross indecency" for homosexual acts
1954 Suicide, age 41


  

"The original question, 'Can machines think?,' I believe too
meaningless to deserve discussion."
ALAN TURING, Mind, 1950

Paul Gray, TIME 100: Computer Scientist ALAN TURING While addressing a problem in the arcane field of mathematical logic, he imagined a machine that could mimic human reasoning. Sound familiar?. , Time, 03-29-1999, pp 147+.

Alan Turing