What went wrong? Why is it that great ages decline? The historian Ibn Khaldun thought the key was the loss of the ethos that binds the rulers to their aristocracies; that luxury, wealth and overconsumption fatally undermine ‘group feeling’. For Gibbon it had been the Christian religion, with its otherworldly eschatology, that eroded the old virtues of Rome. In China, too, there were some, like Du and his contemporary Han Yu, who felt that the ethos had been eroded and that religion was the problem.
