At a time when the public sphere seems saturated by the entertainment industry and "consummate advertising", what remains of the democratic ideal of critical discussion? This book explores the genesis and transformations of public space, from the Athenian agora to the challenges of modernity. Drawing on the work of Jürgen Habermas, the author analyzes the "structural disintegration" of a once bourgeois public sphere, now threatened by media manipulation and citizen passivity. In the face of this decline, he presents the theory of communicative action as a path to refoundation: an invitation to "decolonize the lived world" through the use of argumentative reason, where only the force of the best argument prevails. The originality of this study also lies in the fruitful dialogue it establishes with the great figures of philosophy - from Kant to Marx, from Hegel to Locke - leading to a stimulating confrontation with the thought of Paul Ricour. The latter questions communicative action as a "political utopia", contrasting the ideal Habermasian consensus with the reality of a "conflictual consensus".