The destruction of the [Mongol] invasions, when so much had been lost, led to an intensification of the conservatism that always characterized agrarian society. When resources were limited, it was impossible to encourage inventiveness and originality in the way that we do today in the modern West, where we expect to know more that our parents' generation and that our children will experience still greater advance. No society before our own could afford the constant retraining of personnel and replacement of the infrastructure that innovation on this scale demands. Consequently, in all pre-modern societies, including that of agrarian Europe, education was designed to preserve what had already been achieved and to put a brake on the ingenuity and curiosity of the individual, which could undermine the stability of a community that had no means of integrating or exploiting fresh insights. In the madrasahs, for example, pupils learned old texts and commentaries by heart, and the teaching consisted of a word-by-word explication of a standard textbook. Public disputation between scholars took for granted that one of the debaters was right and the other wrong. There was no idea, in the question-and-answer style of study, of allowing the clash of opposing positions to build a new synthesis.