Chapter 5 examines the crucial role played by Montesquieu in defining national character as a narrative frame. The first section of the chapter focusses on his historical thought and the fundamental role he played in shaping the histoire philosophique – as Hugh Trevor-Roper and, more recently, J.A.G. Pocock have argued. The emphasis is on the importance that Montesquieu attributed to the social and anthropological reasons underlying legal and political changes. In the next part of the chapter the relationship between moral and physical causes in shaping a nation’s character, so central to many of his writings, is investigated. Building on and going beyond the interpretations of Georges Benrekassa and Jean Erhard, the chapter argues that moral and physical causes were both understood by the baron as historical processes – even though of a different nature. National character was at once a result of history and the thread with which the nation’s history could be woven. Through it, moreover, the legitimacy of political institutions could be assessed and their ‘rationality’, as Montesquieu would have said, verified. The final section considers the crucial role played by Montesquieu in the debate opposing the Germanists and the Romanists in the debate over the origins of the French nation.