1. Introduction; 2. Kant's Project of Perpetual Peace; 3. The Project of Perpetual Peace in the Context of the Critical Philosophy; 4. The Evolution of Kant's Thought on International Right; 5. Three Lines of Arguments in Favor of the Federation; 6. Cosmopolitan Protests: A Neglected Middle Term Between Völkerstaat and Völkerbund; 7. Tertium Non Datur: The Problem with Moderate Cosmopolitanism; 8. The 'Sovereignty Dilemma' Reconsidered; 9. Concluding Remarks; References.