Al-Biruni had explained the caste system of India. He did not consider the unique as such social divisions were prevalent in ancient Persia. He accepted the Brahmanical description of the caste system. But he did not accept the notion of pollution. He stated that the state of impurity does not remain for ever. It soon regains its original condition of purity. The sun cleanses the air. The salt in the sea prevents the water from being polluted. But he finds social pollution as contrary to the laws of nature.

Thus we see that Al-Biruni’s description of the caste system was deeply influenced by his study of normative Sanskrit books and the views of Brahmans. However he did not find the system as rigid. For example, the categories like antyaja (born outside the system) provided inexpensive labour to both peasants and Zamindars. Though such classes were socially oppressed yet they were included in the economic network.