Since the second half of the 20th century, rational choice theory (RCT) has gained extraordinary prominence in economics and records a history of powerful applications across the social sciences. Disunity, however, exists among defenders and opponents alike with respect to its nature, status and role in actual economic practice. This disunity has given rise to fundamental disagreements and confusions about the theory’s epistemic potentials and limitations. Drawing primarily on the writings of Jakob Marschak, I show that RCT underwent a fundamental transition after the 1950s that became reflected in its interpretation, application and status within economics. Rather than providing empirically testable hypotheses about human decision-making that would enhance our understanding of actual behavior in the economy, the predefined elements that were taken as constitutive of rational action had been inspired by simple rules of logic that were meant to represent the basic demands of rationality. As such, the rational choice-framework specified a rule of conduct and thereby shaped rather than explained behavior. This transition has given RCT, and economics more generally, a ‘normative turn’, which suggests telling the history of RCT as an account of how rational behavior has, over time, become reinterpreted as rule-following behavior.