WHEN your friends start looking for proofs of your existence, you're heading for trouble. That was God's situation as the millennium got into its stride.

Few ordinary folk, though they had different names for him, doubted the reality of God. He was up there somewhere (up, not down; in his long career, no one ever located him on the seabed), always had been, always would be. Yet not quite so far up, in the churches and monasteries of Europe, many of its cleverest men would soon be racking their brains for ways of proving it.