Before being taken up and amplified — via Karl Mannheim — by the various branches of sociology, the question of ‘generations’ emerged in Germany at the end of the 19th century in the fields of intellectual history (Wilhelm Dilthey) and then of the history of art (Wilhelm Pinder). The challenge was then to identify moments, common spiritual traits or formal registers shared by groups: “the spirit of time” in sum, but broken down into limited empirical fields — generational groups — which are objectivable by the rising humanities, based on their intellectual, artistic and even religious manifestations. This was a way of breaking the philosophy of the history of Hegelian obedience, with the universal red thread of freedom. Since then, the ‘generational’ dimension has played a prominent role in questioning the timing and the forms of socialisation and politicisation of individuals. This article refers first to the intellectual genealogy of this type of question. An analysis of the different aspects of the concept and of the very fact of ‘generations’ is then sought, in particular: (a) generation in the sense of succession and biological offset (fathers/wires); (b) generation in the sense of specific socialisation shared between fathers on the one hand, between the wires of the other, etc.; (c) generation in a strictly political sense: when political events come to structure attitudes and consciences beyond the two previous generational determinations. Finally, we try to configure sociological questions about “generations” within a more general reflection on the timing of political socialisation.