This chapter advances a heterodox reading of ontology that takes inspiration from Heideggerian fundamental ontology and Lacanian psychoanalytical insights about the role of desire and enjoyment in the production of political subjectivities and social order. It reads ontology not as the ground of Being nor as any "in the last instance" material or unobservable structure that grounds a scientific discourse about politics or a fundamental existential outlook on the human condition. Rather, ontology is here understood as the formal non-ground (the void or abyss) of a generative negativity that operates as the condition of possibility/impossibility for the constitution of worldly objects. Such a political ontology emphasises both the impossibility and the necessity of articulating a critical meta-language for a critique of the depoliticised treatment of pluralism in international political thought offered in Chaps.  2– 4. As a corollary to a void ontology, this chapter also proposes a phenomenology of the political that rests on a rehabilitation of messianic nihilism.