Economic theory rests on the principal axiom of egoism; that every action is driven by self interest, and is therefore seen as a moral‐free science. Morality, on the other hand, concerns subjective value judgement, usually in the interpersonal context of whether an action is right or wrong. Although the two are seemingly unrelated, welfare economic theory and its applications cannot proceed very far without the assistance of moral codes. This article discusses the origin and rationale behind the construction of moral codes, the moral codification of preferences and its associated problems.