What does it mean to take rational decisions? Modern decision theory has developed methods to determine the course of action which maximizes the (expected) utility for an agent, given her preferences and beliefs. An agent is said to decide rationally if her preferences conform to the axioms of decision theory, and if she chooses the option which promises to maximize her utility. Axioms such as completeness and transitivity are intended as rational requirements of coherence for preferences. Can thus the normativity of rational choice theory be grounded in the normativity of coherence? And why should coherence be normative?