This PhD thesis focuses on the development of the European Economic Community (EEC) and its visionary idea of Europe since the joint declaration on European identity in 1973. The thesis examines the dual vision for Europe, which aims to establish both an external identity for the European Community in terms of joint external relations, and an internal strengthening of the European spirit among its member states. The thesis adopts a dialectic approach to the issue of identity, considering the interplay between internal and external factors. The theoretical framework draws on constructivist theories of international relations, which are applied in the case study analyzing Japan during the Shōwa era as an external entity reflecting the concept of a common European identity. The academic scope of this interdisciplinary thesis fills an analytical gap in the field, as highlighted in Sophie Huber's 2009 doctoral thesis at the Graduate Institute titled "Polyphonie sur l'identité européenne aux origines d'un discours identitaire 1962-1973". Following Huber's findings, this thesis extends the research beyond the 1973 European Identity Declaration to explore the European external identity and its evolving context, also within the framework of the Cold War and decolonisation. Additionally, the thesis examines the discourses surrounding the idea of Europe in the intellectual milieu. In conclusion, this dissertation offers a dialectic perspective on the intersection of intellectual and political history. It provides insights into how politics, identity, and international relations intersect and mutually influence each other during 20 years of European integration.