Johan Willem Beyen and the creation of the internal market: Lessons from history and the social sciences for the micro-foundations of EU law

Abstract This article formalises and develops an individual-centred framework to explain what I call the micro-foundations of EU law, and applies it to Johan Willem Beyen’s role in the creation of the Common Market. It argues that standard structural accounts in European integration overlook the micro-foundations: the ways in which the desires, beliefs and choices of specific actors shape integration outcomes. Drawing on methodological individualism, mechanism-based causal explanation and narrative legal history, the article reconstructs how Beyen’s liberal economic convictions, his experience in international finance and Bretton Woods institutions, and his reading of the 1930s crisis and post-war power shifts informed his preference for a general common market over sectoral integration. The narrative traces his 1952–55 initiatives, including the Beyen Plan, the Benelux Memorandum and the road to the Messina conference, highlighting environmental, cognitive and relational mechanisms that enabled a small-state minister to set the agenda for the Treaties of Rome. In dialogue with liberal intergovernmentalism and Weiler’s equilibrium theory, the article contends that individual-level explanations, the micro-foundations, provide the ‘prequel’ to both national preference-formation and integration-through-law, enriching structural causal accounts while telling a new story from the perspective of individuals.