The theoretical and methodological framework presented here aims to clarify the various phrases used and in particular the various uses of the terms "generation" and "political generation." We show the extent to which these ideas intrinsically contain a comparative longitudinal component. This has a number of methodological consequences for the study of social movements and of mobilization from a comparative political science perspective. We note, among other things, generational markers as well as the impact of political events and of activism on the socialization of actors.