“Rhetorical action” – the strategic use of rule-based arguments – solves the double puzzle of Eastern enlargement. It provides the causal link between the interest-based state preferences and initial stages of EU and NATO enlargement, on the one hand, and the rule-based final outcome, on the other. “Rhetorical action” draws on a strategic conception of rules that combines a social, ideational ontology with the assumption of rational action; it postulates that social actors use and exchange arguments based on identities, values, and norms institutionalized in their environment to defend their political claims and to persuade their audience and their opponents to accept these claims and to act accordingly. In NATO and the EU, the actors interested in enlargement used the liberal identity, values, and norms of the Western international community to put moral and social pressure on the reluctant member states and shamed them into acquiescing to the admission of CEECs.

In the theoretical chapter of this part (chapter 9), I discuss the conceptual and theoretical foundations of rhetorical action and specify hypotheses about the use and effects of arguments in decision-making. I do this in much greater detail than for the hypotheses of habitual and normative action because rhetorical action plays a pivotal role in my explanation of Eastern enlargement and has received less attention in the rationalist-constructivist debate than the other hypotheses.