This article examines several claims about how James Madison's acquaintance with political theory affected his performance in office. These “theories about theory” come in two varieties: content-based and “nature of theory itself” arguments. The content-based arguments posit that a politician has accepted and used the ideas of a specific political theorist. The nature of theory itself arguments suggest that it is the act of theorizing or applying theory to practice that produces an effect. After describing various examples of each, I introduce a framework for the kinds of evidence required to demonstrate both types of claim. A conclusion outlines what we learn about the effect Madison's penchant for political theory had on his administration. It also suggests that greater attention to these arguments is required to understand the practical effect that political theory has had in the hands of presidents.