In 1924 Maurice Halbwachs published a fascinating book on memory, Les cadres cosiaux de la mémoire. We’ll try to see what does the sociologist remember to explain, what does he forget, and why? What does he blokc out? For, if we now know that to be properly understood, the pain of mourning and of memory should never be disconnected from reflection of their opposites: forgetting and repression, Halbwachs, on the contrary, had forgotten most of it. Moreover, he showed an incredibly strong resistance to and repression of the First World War. The fact is deeply ironic, given that he wrote his first book on memory at the exact moment when “modern memory” was created in the wake of the Great War. The acts of remembering and forgetting are thus subtle and complex choices. Each one operates at the same time in continuity with the past and as a series of selections drawn from it, their interacton constructing a new continuity. For individuals as well as for groups, communities, memory can constitute a burden and forgetting can be seens as a survival tactic. Such was probably true for Halbwachs, hence his “trous de mémoire.”