Today’s European Union (EU) is based on treaties negotiated and ratified by the member states. They form a kind of “constitution” for the Union. The first three treaties, the Treaty of Paris, creating the European Coal and Steel Community (ECSC) in 1951, and the two Treaties of Rome, creating the European Economic Community (EEC) and European Atomic Energy Community (EURATOM) in 1957, were the founding treaties. They were subsequently reformed several times by new treaties, including the Treaty of Maastricht, which created the European Union in 1992. The latest major treaty reform was the Treaty of Lisbon, which entered into force in 2009. Scholarship concerning these treaties has evolved over time. In the early years, it was mostly lawyers writing about the treaties, but soon historians and political scientists also took an interest in these novel constructions in Europe. Interestingly, American political scientists were the first to develop theories of European integration; foremost among these was Ernst Haas, whose 1958 book The Uniting of Europe developed the theory later referred to as neo-functionalism. The sector on integration of coal and steel would have an expansive logic. There would be a process of “spill-over,” which would lead to more integration.It turned out that integration was less of an automatic process than suggested by Haas and his followers. When integration slowed down in the 1970s, many political scientists lost interest and turned their attention elsewhere. It was only in the 1980s, when the internal market program gave European integration a new momentum that political scientists began studying European integration again from theoretical perspectives. The negotiation and entry into force of the Single European Act (SEA) in the mid-1980s led to many new studies, including by American political scientist Andrew Moravcsik. His study of the SEA included a critique of neo-functionalism that created much debate. Eventually, in an article in the early 1990s, he called his approach “liberal intergovernmentalism.” It took final form in 1998 in the book The Choice for Europe. According to Moravcsik, to understand major historic decisions—including new treaties—we need to focus on national preferences and interstate bargaining.The study of treaty reforms, from the SEA to the Lisbon Treaty, conducted by political scientists—including the treaties of Maastricht, Amsterdam, and Nice—have often contrasted neo-functionalism and liberal intergovernmentalism. But other approaches and theories were developed, including various institutionalist and social constructivist frameworks. No consensus has emerged, so the scholarly debates continue.
1. Introducing the Mosaic of Integration Theory