The importance of rational institutionalism in the analysis of informal international institutions

The study of informal international institutions has advanced considerably over the past decade. Much of this work, including our own, has approached this phenomenon from the perspective of rationalist institutionalism. Yet, existing work has also been criticized from several conceptual, theoretical, and empirical angles. The recent special issue of International Politics on the "cascading dynamics" of informality by Cooper et al. (Int Politics, 2022, https://doi.org/10.1057/s41311-022-00399-4) offers an important example of such critiques. It builds on earlier work in the field, advancing our understanding of a number of processes and institutions, but also partly casts itself as a reaction to the approach we have adopted. We argue that key aspects of this critique are misguided and that Cooper et al. exaggerate the differences that divide us. Our aim in this article is to respond to their criticisms, clarify the key research issues at stake, emphasize the complementarities among approaches, and outline ways of moving forward.