In this part, I have developed and applied a community approach to enlargement on the basis of sociological institutionalist assumptions. According to this approach, states seek to join and are admitted to regional organizations if they share the identity, values and norms of the international community these organizations represent. NATO and the European Union are European organizations of the Western international community. I therefore hypothesized that they would admit those CEECs which have come to share the liberal identity of the Western community and have internalized its liberal norms of domestic and international conduct.

To evaluate the community approach and the liberal community hypothesis, I have drawn on three kinds of empirical evidence. First, the formal rules of NATO and the EU show that liberal identity, values, and norms are constitutive for the organizations and their enlargement. Second, the official discourse on enlargement demonstrates the organizations' commitment to their community-building mission and the priority of the liberal community rules as criteria for the selection of new members. Third, on the behavioral dimension, the selective establishment of institutional relationships and the opening of accession negotiations with the CEECs seems to be strongly correlated with the degree to which CEECs comply with the community rules and have institutionalized liberal democracy.

On this evidence, the community approach is able to explain why the Western organizations are prepared to admit CEECs in spite of net material costs for their members.