The Vedas are compared to the desire tree because they contain all things knowable by man. They deal with mundane necessities as well as spiritual realization. The Vedas contain regulative principles of knowledge covering social, political, religious, economic, military, medicinal, chemical, physical and metaphysical subject matter and all that may be necessary to keep the body and soul together. Above and beyond all this are specific directions for spiritual realization. Regulative knowledge involves a gradual raising of the living entity to the spiritual platform, and the highest spiritual realization is knowledge that the Personality of Godhead is the reservoir of all spiritual tastes, or rasas.