dharmasya pādāś catvāras
Eating, sleeping, defending and mating are the four principles of material bodily demands which are common to both the animals and human society. To distinguish human society from the animals there is the performance of religious activities in terms of the social statuses and orders of life. They are all clearly mentioned in the Vedic literatures and were manifested by Brahmā when the four Vedas were generated from his four mouths. Thus the duties of humankind in terms of the statuses and social orders were established to be observed by the civilized man. Those who traditionally follow these principles are called Āryans, or progressive human beings.