This chapter focuses on expected utility theory, which is the major normative theory of decision making under risk. It presents sharper tests of invariance in which the two versions of a given choice problem are unquestionably equivalent. The chapter suggests that the more successful practitioners of the art of persuasion commonly employ such framing effects to their personal advantage. It shows that people often fail to distinguish between causal contingencies and diagnostic contingencies. The chapter deals with the perception and the weighting of chance events and the role of uncertainty in choice. It addresses the classical issue of the rationality of voting. The chapter critically examines a rational analysis based on the probability of casting a decisive vote with a less rational analysis that incorporates an element of self-deception. It analyses the rational analysis of political decision making with a psychological account based on descriptive considerations.