The basic structure is coherent: It has an orderly or logical relation of parts that is recognizably unique and that allows us to differentiate that structure from others. With the introduction of the concept of time, ideas such as direction, sequence, character development, and story line enter into the concept of continuity as it is applied to the evolution of a human being. In this theory, a dynamic concept of continuity is developed and applied to the issue of adaptation to normal aging.[42]