Whence American Internationalism

This is the authors' abstract. We don't add key points for this paper.

One of the most important puzzles of twentieth-century international relations is why the American conception of security vis-à-vis the European Powers shifted from unilateralism to internationalism after World War II but not after World War I. In this article I document that this shift was measurably one of collective ideas and explain the transformation. Scholarship on the sea change in American global thinking has been hampered by the lack of attention to the broader issues of when and why collective ideas change. To address this gap I offer a general framework to account for ideational change: I highlight the interaction between collective ideas and events that allows individuals and societies to overcome barriers to ideational change in some circumstances but not others. This argument clarifies the otherwise puzzling development of American ideas and offers a template for understanding change in other areas.