If we know that certain ways of making decisions are associated with real-life success, is this then how we should decide? In this paper the relationship between normative and descriptive theories of decision-making is examined. First, it is shown that the history of the decision sciences ensures that it is impossible to separate descriptive theories from normative ones. Second, recent psychological research implies new ways of arguing from the descriptive to the normative. The paper ends with an evaluation of how this might affect normative theories of decision-making.