This working paper investigates the reasons underpinning the growing use and widespread resonance of the concept of 'civilizations'defined by cultural and religious markersin scholarly, policy and public discourses, since the end of the Cold War. Such an inquiry is made all the more relevant since the concept of civilizations has not only remained at the level of language. It has, in fact, become embedded, instantiated, and operationalized within the global governance architecture, most prominently with the creation of the UN Alliance of Civilizations (UNAOC) in 2005. The UNAOC represents a remarkable development in the way international order is being understood and upheld within global governance institutions, as no longer solely dependent on states, or on the advancement of individual rights and economic opportunities, but also on what occurs between and within civilizations. Why have discourses and practices about civilizations acquired the political salience they have in international society at this historical juncture? This paper argues for an understanding of the concept of civilizations as a particular kind of 'empty signifier', underpinned by three overarching logics: a logic of interpretation centered on identity, a logic of critique towards liberal 'end of history' narratives and projects, and a logic of practicality that matches the interests of multiple state and nonstate actors. This argument is empirically illustrated through an analysis of how these three logics, which explain the contemporary power and authority of the signifier of civilizations, also structure the mission, bureaucratic apparatus, and operations of the UNAOC.