When a person’s physical form has fully developed, he will develop spiritual activity accordingly. Here “form” refers to the physical form of a human being, and “spiritual” refers to various mental activities, including emotions and consciousness. Xunzi (313-238 BC) pointed out that a person’s physical form and spirit, just like everything else, develop naturally in the course of the movement of the way of heaven. Spirit is born in the wake of physical formation of a human being. Full physical form is a prerequisite to the birth of spirit. A person’s spirit exists within his physical form.