When I was a small boy, I used to read science fiction. Even after more than sixty years, one story stays in the memory. Scientists had built a wonderful computer, far more powerful than any rival and also far larger. This was before the era of miniaturisation, so the machine was said to be the size of a hill. The world’s most learned men assembled and drew lots to decide who would have the first question. The world waited agog as the winner asked the computer whether there was a God. The reply was instantaneous. “There is now”.

Cut to AI. One philosophical question is being raised. Could a man-made machine somehow evade ultimate human control? For what little it is worth, I think that the answer must be “no.” But even a technology firmly under control might have the most dramatic effects, some of them dangerous.