The origins of European integration and the factors that made it possible in the post-1945 era have been examined from different perspectives and interpreted in various ways. While federalists argue that the concept of European unity had been developed over centuries by different intellectual movements, the realist approaches of Milward and Dinan stress the importance of economic, political and security motives. Referring to the factors that contributed to the implementation of the Schuman Plan, both the federalist and realist approaches highlight the chief importance of states and their representatives. Yet, the ideas that inspired Jean Monnet, who designed the Schuman Plan, have received little attention. While the state is seen in the literature as the main actor that made the outcome possible, the role of Monnet and that of some of his close associates are almost ignored. By investigating Monnet's thought, this study shows that the source of his inspiration was not the countless plans for European unity put forward by European federalist movements or the random concepts that he came across, such as the New Deal. Rather, it is argued here that he was in fact constantly exposed to a coherent and well-structured philosophy. This thinking reached him through his direct contacts and frequent encounters with Felix Frankfurter and his associates, who formed an epistemic community, as defined by Peter M. Haas. The core concepts of this thinking inherited from Louis Brandeis and developed by Frankfurter – restoring and overseeing free competition – can be identified in Monnet's 1950 plan. The evidence shows that it became a shared philosophy of Monnet's group of friends. This is a fundamental aspect since, once the Schuman Plan was made public, Monnet's friends rallied around his project and contributed not only to overcoming stalemate at critical moments of the negotiations on the future treaty, but also to convincing statesmen of the value of the project. / Graduate