Theorising European integration: the four phases since Ernst Haas’ original contribution

Ever since Ernst Haas' ground-breaking work on European integration, scholars have been theoretically divided over who or what are the drivers of European integration, mainly between supranationalism or intergovernmentalism. Cutting across the substantive divides have also been differences in analytic frameworks, including rationalist/rational choice institutionalism, historical institutionalism, and constructivist/discursive institutionalism. These cross-cutting methodological cleavages have played out in successive phases of substantive scholarly theorisation, even as alternative developments in theory and practice involving deepening integration and increasing politicisation have complicated such theorizations. While the first phase (late 1950s-1970s) was methodologically pluralist as it divided between neofunctionalist supranationalism and realist intergovernmentalism, subsequent phases were clearly divided also by methodological approach. The second phase (beginning in the 1990s) mainly divided between historical institutionalist supranationalists and rational choice institutionalist liberal intergovernmentalists. The third phase (beginning in the 2010s) divided between 'new' constructivist/discursive institutionalist supranationalists and 'new' constructivist/discursive institutionalist intergovernmentalists. The fourth phase (in the mid to late 2010s) takes greater stock of increasing politicisation while dividing between rationalist/historical institutionalist post-functionalists and constructivist/discursive institutionalist post-functionalists. The conclusion asks how these divides could be more fully bridged in order to achieve more substantive and methodological pluralism.