Macro-prudential thinking and its emphasis on endogenously created systemic risks, marginal in the banking regulation discourse until the mid-2000s, has become central post-crisis. This paper analyzes this intellectual shift by using discourse and citation-network analysis of the most-cited scholarly works on banking regulation and systemic risk from 1985 to 2014 and six in-depth interviews with central scholars. It demonstrates that the predominance of formalism, particularly partial equilibrium analysis, in studies on banking regulation pre-crisis impeded economists’ engagement with the endogenous sources of systemic risks discussed in the systemic risk sample. These studies excluded observed phenomena that could not be accommodated in mathematical models, largely ignoring contributions based on historical and practitioners’ styles of reasoning. Post-crisis, while informal analyses gain prominence in studies on banking regulation, attempts to conceptualize systemic risk as a negative externality indicate the persistence of formalism and equilibrium thinking and its concomitant epistemological limitations that stymie theoretical progress.