Political theory lags behind other subfields in political science in rigorously testing what helps foster critical thinking (CT). Yet some of the greatest temptations to engage in motivated reasoning can be found in normative political contexts. This study uses multiple regression analysis to explore nine semesters of data from an introductory course in political theory. Three results stand out: (1) as the stakes of an assignment decrease, so do CT scores; (2) as the number of course assignments increase, CT scores fall; (3) when preparatory exercises matter, theory-specific CT exercises outperform generic ones. A theory of student rationality is put forth. Implications for course design, program assessment, and future research are discussed.