Computing machinery and intelligence

"I propose to consider the question, 'Can machines think?'" Alan Turing opens the October 1950 issue of the philosophy journal Mind with that line and then declines to answer it, because the words are too vague. In its place he offers a game. An interrogator types questions to two hidden parties, one human and one machine, and tries to tell which is which. If the machine fools the interrogator as often as a man pretending to be a woman would, the question of thinking has been settled in the only way that matters.

The paper is more than the test. Turing works through nine objections, theological, mathematical, the argument from consciousness, Lady Lovelace's claim that a machine can only do what it is told, and answers each. In the final section he makes a proposal that took half a century to look reasonable: rather than programme an adult mind, build a child mind and educate it. "We may hope that machines will eventually compete with men in all purely intellectual fields."

He guessed that by the year 2000 a machine with about 10⁹ bits of storage would pass his test thirty percent of the time. The storage guess was low and the date was early, but the structure of the argument, that intelligence is a matter of behaviour rather than substance, is the ground the whole field stands on.