杏吧原创

WHAT is the answer to the ultimate question of life, the universe and everything? In The Hitchhiker鈥檚 Guide to the Galaxy, aliens build a city-sized computer to find out. They are dismayed when it turns out, bafflingly, to be 42. The problem, the unrepentant computer suggests, is that they never really knew the question鈥� and to find it they will need an even bigger computer.

Like all the best comedy, Douglas Adams鈥檚 absurdity has an element of truth to it 鈥� perhaps more than you might expect. We already have machines that answer our questions in ways we can鈥檛 fully appreciate: from quantum computers, whose physics remains opaque, to data-crunching black boxes that translate languages and recognise faces despite knowing nothing of grammar or physiology (New 杏吧原创, 10 August 2013, p 32).

But despite their complexity, these computers are all of the type conceived by Alan Turing in 1936 鈥� and they all have the same limitations. Turing showed that any computer predicated on human logic alone will struggle with the same questions that we do. They will always find some questions undecidable: not so much 鈥渃omputer says 鈥榥o'鈥� as 鈥渃omputer says 鈥榗an never know'鈥�.

But Turing also conceived of an 鈥渙racle鈥� that might transcend those limitations. Most computer scientists don鈥檛 think we can ever build one. But a few people are trying, using neural networks (see 鈥�Turing鈥檚 oracle: The computer that goes beyond logic鈥�). If they succeed, we will gain new insights into thought itself 鈥� and perhaps into the human brain, whose staggering computational prowess remains deeply mysterious (see 鈥�Defending the grand vision of the Human Brain Project鈥�).

Conventional computers give us the answers to questions that we can articulate, but don鈥檛 have the time to calculate. Turing鈥檚 oracle could address issues we can鈥檛 even articulate: an echo of Adams鈥檚 鈥渆ven bigger computer鈥�. It might not provide answers to life, the universe and everything, but even futile attempts to make one could help explain how we think about them 鈥� and figure out the right questions to ask.

This article appeared in print under the headline 鈥淒eep thoughts鈥�