The finality of this paper is not to analyse the principle of political responsibility in all of is dimensions. To opt for such a perspective would require developments that would go beyond the context of this work. This is why the author of this paper preferred to try and shed light not on the use or the praxis of political responsibility as it is conceived today, as it belongs to specific philosophies of action, that answer to contradictory power logics, but on the intellectual and ideological considerations underlying the genesis of this notion today. In order to achieve this, the author makes a detour through the classical definition of responsibility first, notably as seen by the American realist school. As the author observes that usage apparently questions this traditional definition, he then lays stress on the genesis and the consequences, before he suggest a new dialectic of threat and responsibility. – Summary AFRI-2005