In this monograph the question of identity is preceded by the epistemological question of the disciplines that have really defined who we are: comparative law and international law. The book aims at satisfying not only the need of investigating the question of identity, but of constructing a epistemological legal paradigm of the relation with the Other. It is composed by three parts. The first one deals with International (and closed) State identity. The second one analyses the European legal space origins and consolidation. The third section is about the edification of a relational dimension of European Union identity against populism backlash and will end with some epistemological conclusions.