Multiplicity exists everywhere, in any dimension, on any level, among everybody, since the dawn of time. Until recently, Western culture preferred to marginalize, contain or appropriate multiplicities, grinds them to pieces against the One. Pagan gods were exchanged for the “only truly god”; Sophists relativism diminished before Truth. In modern times the One appeared under the guise of the Self, the Individual, the Subject or the Nation.   Even critical theory joins the party and regards the capitalist logic as the only one that prevails in social life. I attempt to show in this seminar some fundamental aspects of the historical and current quarrel between multiplicity and the One, taking as my point of reference thinkers like Deleuze, Foucault, Nietzsche, Hardt and Negri, etc.