 In one way or another, all theories regarding the structure of concepts are developments of, or reactions to, the classical theory of concepts. According to the classical theory, a lexical concept C has definitional structure in that it is composed of simpler concepts that express necessary and sufficient conditions for falling under C. The stock example is the concept BACHELOR, which is traditionally said to have the constituents UNMARRIED and MAN. If the example is taken at face value, the idea is that something falls under BACHELOR if it is an unmarried man and only if it is an unmarried man. According to the classical theory, lexical concepts generally will exhibit this same sort of definitional structure. This includes such philosophically interesting concepts as TRUTH, GOODNESS, FREEDOM, and JUSTICE.