The 20th century saw an unprecedented number of major wars, conflicts, and massive human rights violations. From each emerged the desire to make sense of the recent past (and present) by imagining new ways of dealing with such events. In order to prevent new forms of violence, or to punish the persons responsible of past horrors, various solutions have been imagined, deployed, implemented, and discussed, at different levels. This book is a reflection on the social and historical construction, appropriation, and circulation of categories, norms, and savoir-faire related to the ways social groups and institutions--state, judiciary, professional organizations--confront traumatic events. Even if there is a robust literature on purges and other mechanisms intended to deal with an authoritarian or violent past, written by authors belonging to numerous disciplines and exploring different periods and topics with a variety of theoretical and methodological backgrounds, our goal was to propose a more sociologically oriented model of analysis. Far from being only an intellectual frenzy, this orientation appears to be less normative than most "post-transitional" approaches and potentially more general than strictly monographic approaches. In doing so, our objective is not only to provide a critical approach, but also to sustain a more realistic view of this highly political and moral domain.