In many disciplines, including economics and philosophy, a normative statement expresses a value judgment about whether a situation is desirable or undesirable. Whereas a descriptive statement (also known as a positive statement) is meant to describe the world as it is, a normative statement is meant to talk about the world as it should be. For instance, "the world would be a better place if the moon were made of green cheese" is a normative statement because it expresses a judgment about what ought to be. Normative statements are characterised by the modal verbs "should", "would", "could" or "must". In economics, normative statements form the basis of normative economics.