This article deals with the concept of modernity upon which one of the most interesting contemporary theories about modern social change is based—Peter Wagner's theory of successive modernities. Wagner understands modernity as a double imaginary signification which entails a basic tension between liberty and discipline. This conception is almost directly taken from Cornelius Castoriadis. I argue that this tension exists in two versions in Castoriadis' philosophy and that the two versions are incompatible. It is further claimed that the two versions reappear in Wagner's theory, which makes his theory of successive modernities partly inconsistent. A stance is taken for one of these versions and it is argued that the theory of successive modernities should appropriate that version as its point of departure in order to grasp the history of modernity in a consistent way.