Traditional theory uses expected utility to explain gambling and insurance, only to result in numerous contradictory examples. Its reliance on increasing marginal utility also violates basic economic principle. Its inability to reject unfair games or insurance policies is dangerous. This book works out a new theory that is in line with Economics. It maintains the diminishing marginal utility foundation, explains also gambling and shows how to reject unfair games and policies. More importantly, it proves that there is no such thing as expected utility.