The present article aims to show how the consolidation of the cinematic form of the essay film in Jean-Luc Godard’s work is a consequence of the evolution of his experience in the cinéma militant, which emerges from the political and social circumstances that caused May 68. In the case of the filmmaker it is materialised through his participation in the Dziga Vertov Group. The defining elements of the group’s filmic experience – the supremacy of montage, the dialectics between images and sounds and the relevance of the spectator as an active part of a dialogic practice – are the same that bring about the essayistic form when the film is enunciated from the author’s subjectivity. With the analysis of Letter to Jane this paper tries to demonstrate how the emergence of subjectivity in the revolutionary cinematic practice allows the appearance of self-reflexivity and the thinking process that define the essay film.