This book explores cosmopolitanism's radical dynamic as expressed in the struggles from below, all over the world, against exclusion and domination, pointing to the horizon of another world that appears possible. It shows that cosmopolitanism emerges negatively through disaffiliation from the given forms of belonging and by questioning of the existing meanings and unjust practices. Through a radical critique, cosmopolitanism goes to the roots of the existing world order based on the nation-state, exposes its exclusionary structure, and brings instead the idea of a World Republic where No One Is Illegal and where all are equal citizens of the world. Caraus captures this radical dynamic in a cluster of novel concepts, such as 'cosmopolitanism of dissent', 'post-foundational cosmopolitanism', 'cosmopolitan ontology', 'institution of critique', 'radical cosmopolitical love', all integrated into an approach of a militant and radical cosmopolitics that reclaims the legacy of the first cosmopolitan stance of the Ancient Cynics.