The question of the political regime is at the heart of the work—and one could say the life—of Raymond Aron. The thinking of this French philosopher and sociologist demonstrates how and to what extent this question is at the heart of the human problem qua political problem. Aron's lucidity in the face of a century marked by hyperbolic drama and process, by extreme hopes and fears, is well known. It is useful to recall the starting point of his intellectual journey in order to introduce our reflection on the science that informed his judgment of historical actuality.