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A-Z of Ideas: Turing

Kester Brewin

AZTuring.jpgAlan Turing was an atheist homosexual who made perhaps the single most impor- tant contribution of any individual in turning the course of World War Two. His work was hushed up by the government, who forced him to be injected with oestrogen to neutralize his 'unnatural state.' After therapy proved unhelpful he committed suicide.

These biographical details show us the context of Turing's core area of thought: to what extent is the human mind a machine, and to what extent will a machine ever imitate the human mind? After two world wars these were important questions. Soldiers had been treat- ed as disposable fighting machines in WW1, and machines had mechanically processed the deaths millions in WW2. Turing's ideas were thus directed at the anxieties of 1950's Britain, and to the bodily paradox he felt acutely: this 'bag of inanimate molecules reordered into a man.'

His first major work gave an answer to the Entscheidungsproblem: the question of whether it would be theoretically possible to discover by logical processes alone whether any statement was true or false. With his thought-experiment using a theo- retical machine that read symbols on a tape he proved this in the nega- tive: there existed problems that could not be computed.

Technologically, this was a huge breakthrough that led directly to the development of modern computers. Philosophically, it opened up a whole new area of thought: if computability has limits, then do human beings have properties like responsibility and authority that other objects are unable to possess? Turing's own view was based around appearance: it did not mat- ter whether God, if he even existed, could give a machine a soul; what mattered was whether a machine could be built that could convince a human being that it had a soul.

He proposed the 'Turing Test,' whereby a person interrogated a human and a machine hidden behind a screen. If within five min- utes the person is unable to discern which is which, the machine has passed the test and the machine is said to be 'thinking.' Current human thinking predicts that such a machine may exist by 2029. One paradox Turing identified in this test is 'If a machine is expected to be infallible,' he said, 'it cannot also be intelligent.' Part of what it is to be human is to get to solutions by making mistakes.

The world he lived in was unable to see his humanity as anything other than broken, and prescribed machine-like solutions to 'fix' his sexuality. He was pardoned in 2009, and in a world where cyborgs are nearing reality, clarity of thought about the difference between human and machine is needed more than ever.

Kester Brewin