What does development mean? What factor has enabled some societies to enjoy the benefits of the modern world, growth and progress? Economists and sociologists from Adam Smith and Karl Marx to Max Weber and Fernand Braudel have tried to find an explanation for "the wealth of nations" -- or their poverty. Most thinkers have focused on material explanations such as capital, work, natural resources, and climate. Alain Peyrefitte suggests another explanation: What if mental attitudes and behaviour were the main causes of development -- and of underdevelopment?In order to examine the viability of his hypothesis, Peyrefitte reviews the history of western Christianity from the fifteenth to the eighteenth century. He demonstrates that development in Europe was the result of an "ethos of confidence", which he defines as a mental disposition encouraging the questioning of traditional taboos and favouring innovation, mobility, competition, and responsible and reasoned initiative.According to Peyrefitte, we must rediscover the "ethos of confidence". But how? Alain Peyrefitte is a member of the Académie Française and of the Académie des Sciences Morales et Politiques.