This paper examines the French epistemic marker JE SAIS [I know] in a ten-hour video-recorded corpus of public and TV debates. A statistical survey reveals only a dozen tokens, which appears to be a low frequency both in comparison with other expressions such as ON SAIT [one/you/we know] or JE SAIS PAS [I don’t know] and considering the interactional and argumentative properties of debates, as identified by previous research. Bringing together insights from Interactional Linguistics, Enunciative Linguistics and Argumentation Theory, the paper scrutinizes the enunciative and argumentative unfolding of the turn in which JE SAIS operates. The analysis highlights the polyfunctional dimension of the resource, which cannot be reduced to the self-attribution of a state of knowledge.