Political violence has previously been understood, by media and by politics, as a result of a subjective "swing". Social sciences view this commitment as "high risk activism". To test the validity of this interpretation, we carried out a sociological survey centered on the French extreme left wing. Based on these interviews, we propose a conception of radical commitment characterized by two properties: firstly, the fact of being an integral part of a life course, and secondly the fact of acting out one's personal convictions and being driven by a moral duty. Therefore we propose a critic of the "swing" interpretation and show that, for the extreme left wing, the crucial point is an irreversible awareness which, nevertheless, is part and parcel of the continuity of a biographical trajectory. These two properties suggest a new characterisation of radical commitment as regards that proposed by Doug McAdam (1986), in terms of "high risk" and "high cost", still referred to currently (Sommier, 2012).