The aim of this article is that of bringing the inextricably ontological and political enjeu of Agamben’s work into light, through the investigation of the beginning of the Homo Sacer series and of the shift that such a beginning produces within the author’s philosophical project. More precisely, through a comparison of the first two texts of the series, Homo Sacer. Sovereign Power and Bare Life, Homo Sacer I (1998) [1995], and State of Exception, Homo Sacer II, 1 (2005) [2003], we will show how, in many respects, the philosophical question raised by Agam-ben in the first volume proves to be problematic, although it finds its most precise formulation in the period of time which spans from the first volume to the second. Our hypothesis is that the punctual recovery of the main inquiries of Homo Sacer I within State of Exception and, in particular, the recovery of the strategic interpretation of the debate between Carl Schmitt and Walter Benjamin, coincides with a crucial in-depth analysis that allows Agamben to introduce the paradigms of inoperativity and use in the specific meaning that these terms have in the sub-sequent developments of the series, i.e., as key notions through which Agamben elaborates his philosophical rethinking of the nexus between ontology and politics.