A wave of recent scholarship, embracing both rational choice and cultural approaches, highlights the importance of collective ideas in explaining politics. What this work has not adequately addressed, however, is why collective ideas sometimes radically change. Scholars typically attribute ideational change ad hoc to creative entrepreneurial agents or to exogenous shock. But these solutions fail to account for why some entrepreneurs and not others are successful in marketing their ideas or why similar shocks lead to change in one instance but continuity in another. Explaining these Variations is aided by conceptualizing ideational change as a two-stage process involving collapse and consolidation. Collapse involves societal actors reaching an agreement that the old orthodoxy is inadequate. Consolidation requires social coordination on a replacement set of ideas. Both steps involve collective ideation problems where actors may have difficulty coordinating a change in dominant ideas or have incentives to shirk facilitating efficient adaptation. The outcome of these two steps is in part endogenous to ideational structure :itself. Collective ideas generate expectations, which in particular ways interact with experienced events, either inhibiting change or allowing societies to transform their own dominant notions. The approach is illustrated with examples involving collectively held causal ideas in a variety of foreign policy domains.
