Part I provides the theoretical framework of the book and presents the propositions to be evaluated in the comparative study. I briefly discuss the two major approaches to the study of the domestic impact of Europe dominating the literature: “resource dependency” and “institutional adaptation”. The two approaches entail different understandings of how institutions affect actors' behavior. Resource dependency usually draws on some form of rational choice institutionalism, which conceives of institutions as constraining and enabling specific choices and strategies of rational actors striving to maximize their self-interests. Institutional adaptation is firmly rooted in sociological institutionalism, which emphasizes the social or cultural aspect of institutions. Institutions do not only constrain and enable actors' behavior. Institutions entail collectively shared systems of meanings (institutional culture), which constitute actors by providing them with fundamental understandings of what their interests and identities are.

Due to their distinct understanding of institutions, resource dependency and institutional adaptation identify different causal mechanisms by which Europeanization affects the institutions of the member states. They generate different empirical validity claims on the conditions of change, the process of change, and the degree and outcome of change. But rather than testing these empirical validity claims against each other, I strive to combine theoretical assumptions of resource dependency and institutional adaptation in a historical institutionalist approach to Europeanization and domestic institutional change. I argue that both the instrumental and the cultural dimension of institutions have to be taken into account in order to understand Europeanization and its domestic impact.