This article challenges the idea that the Schuman Declaration of 9 May 1950 was a break with ideologies of the past. It traces the political economy of the declaration from the interwar to the post-war period. It reconstructs the conceptions of economics and politics that underlay the proposal, tracing them back to the once influential corporatist and communitarian ‘third way’ ideology. It then shows that the original intent of the declaration was nevertheless crushed by a powerful dynamic of institutionalisation of transnational parliamentarianism. Thus, the article demonstrates the effects of long-lasting cleavages on the institutionalisation of European organisations.