Defence date: 22 November 2011Examining Board: Professor Donatella della Porta (EUI, Supervisor); Professor James Jasper (City University of New York); Professor Michal Keating (EUI, University of Aberdeen); Professor Lilian Mathieu (Ecole Normale Supérieure, Lyon)PDF of thesis uploaded from the Library digital archive of EUI PhD thesesThis research investigates an often forgotten aspect of collective action, its imaginary dimension, by focusing on an overlooked concept: utopia. According to me, utopia is both a form of discourse and a set of particular practices. Thus, to be called utopian, a discourse has to include, first, a rejection of the existing society, and second, if not a clear conception of what another world might look like, at...