Informations and abstract
During the last years secession has become a central theme either in the scientific reflection or in the public debate. All the disciplines that pay attention to the society (philosophy, political sciences, sociology, law, economy) took risks of analysing the phenomenon, and described its various dimensions: legitimacy, ways of accomplishment, causes, solutions. Very often secession has been confused or included in the analyses of nationalism and self-determination. In the essay the different features of the phenomenon and the theories the sociologists propose to explain it are analysed. Among these the rational choice theory seems to have the best heuristic power, since it tries to hold the different aspects of the phenomenon together, the bonds, the strategies, the resources. This theory seems to be very useful from an analytical point of view, but it is less effetive from a predictive one. Much work remains to do to understand a phenomenon destined to have a growing importance.