With the "End of History," the revolution seemed to become obsolete as a subject of political practice and theory. However, in light of the various crises of recent years, the question of possibilities and conditions for radical political-social transformation is regaining relevance. Particularly in light of the experiences of the Arab Spring and the Occupy movement, a systematic examination of significant models of revolution from Rousseau, Jefferson, and Kant to Marx, Arendt, and further to Balibar and Graeber is warranted. To relate the heterogeneous approaches to one another, this introduction focuses on fundamental problems that every theory of revolution must address: these include the issues of novelty, freedom, violence, and the revolutionary subject.