According to Vedic literature, the superior and inferior varieties found in the human social system, varṇāśrama, are due to pious and sinful modes of family planning. Thus piety and sin are constant points of reference in the Vedic analysis of the components of a given situation — namely the material ingredients, place, age and time. Indeed, the Vedas reveal the existence of material heaven and hell, which are certainly based on piety and sin.