It is often assumed that cosmopolitan thinkers since the Renaissance have simply adopted and refined concepts from classical antiquity. This study argues that modern European cosmopolitanism should be perceived as a unique phenomenon, distinct from Greek and Roman forms of cosmopolitan thinking. One key feature is its dynamism, or the idea of change built into modern theories of cosmopolitanism. Covering the period from the 1530s to the 1920s, this book investigates various manifestations of cosmopolitanism, including normative individualism, the dawn of historical thinking, and the dynamic conceptions of law and rights and of the international community. It analyses the international legal theories of selected authors from Francisco de Vitoria to Austrian lawyers Heinrich Lammasch and Alfred Verdross. The author focuses in particular on the development of hospitality rights and the right to immigration, republicanism and cosmopolitanism, and cosmopolitan education.