This article examines the normative presumption in Rational Choice Theory (RCT) as a tool to understand the actions of protagonists, as an analytical framework for the normative assessment of actions taken and as a theory capable of explaining and/or predicting them. It employs instrumental rationality techniques to provide an account of the conceptual and prescriptive justification of the presumption. The article argues against the claim of Prospect Theory (Kahneman and Tversky) according to which the normative presumption undermines the normative power of RCT. The article also discusses some common and mistaken claims about the proper theoretical scope and application of RCT.