Jeffrey C. Alexander is the Lillian Chavenson Saden Professor of Sociology at Yale University, Connecticut. His writings over the last three decades have been foundational to the new discipline of cultural sociology, and his seminal work The Civil Sphere (2006) has come to be regarded as the major sociological theory of democracy. He founded and co-directs the Yale Center for Cultural Sociology. He has authored and edited more than fifty books, and his work has been translated in almost thirty languages. Trevor Stack is Senior Lecturer in Spanish and Latin American Studies at the University of Aberdeen. He is Director of the inter-disciplinary Centre for Citizenship, Civil Society and Rule of Law (CISRUL), which focuses on the study of political concepts in the world. Currently he leads a large (Economic and Social Research Council) ESRC project on Activism in Violent Regions, as well as an EU Marie Curie COFUND grant on Political Concepts in the World. Farhad Khosrokhavar is retired professor at the École des Hautes Études en Sciences Sociales, Paris and a director of Observatoire de la radicalisation in the Fondation de la Maison des Sciences de l'Homme, Paris. He has published twenty-seven books, five of which are in English; his work has been translated into ten languages.