Starting from pragmatic models of communication inspired by philosophy (K.O. Apel, F. Jacques, P. Ricoeur), this ppaper approaches the question of dialogue by reference to the theorization of language activity according to the linguistics of enunciative operations (A. Culioli). Expounding a system of metalinguistic representation focused on the key concepts of assertion and commitment led the author to present a schematization of the discursive space of discussion, by means of an oriented graph. This topological standpoint meant that exchanges in dialogue, with its entrances and exits, could be simulated. The analysis of a debate between two economists on a subject about which they disagree is used to illustrate the theoretical premise. The ethics of dialogue thus no longer resides in a transcendental instance but in the very exercise of speech, in the listening to oneself and to the other.