This dissertation develops a sociological theory of emotions that relies on a conception of social action that involves rationality, normativity, and emotions. The theory is used to treat the problem of the emergence of norms and to provide answers to the questions “Why and How do norms emerge?” The political collective Occupy Geneva (Les Indignés), conceived as a small-scale society, allows to empirically study this problem. It is shown that the creation and adoption, by the members, of norms of punishment, exclusion, protection from danger and reintegration of the expelled members resulted from collective deliberations and actions motivated by various collective emotions (respectively and notably indignation, contempt, fear and forgiveness) that were inscribed in the institutional background of the collective (principles of deliberative and participatory democracy, and contractualism). The central argument states then that social norms have emotional foundations.