linguistic:voice_change
History of religions

Biruni is widely considered to be one of the most important Muslim authorities on the history of religion. He is known as a pioneer in the field of comparative religion in his study of, among other creeds, Zoroastrianism, Judaism, Hinduism, Christianity, Buddhism and Islam. He assumed the superiority of Islam: "We have here given an account of these things in order that the reader may learn by the comparative treatment of the subject how much superior the institutions of Islam are, and how more plainly this contrast brings out all customs and usages, differing from those of Islam, in their essential foulness." However he was happy on occasion to express admiration for other cultures, and quoted directly from the sacred texts of other religions when reaching his conclusions. He strove to understand them on their own terms rather than trying to prove them wrong. His underlying concept was that all cultures are at least distant relatives of all other cultures because they are all human constructs. "Rather, what Al-Biruni seems to be arguing is that there is a common human element in every culture that makes all cultures distant relatives, however foreign they might seem to one another."

Al-Biruni divides Hindus into an educated and an uneducated class. He describes the educated as monotheistic, believing that God is one, eternal, and omnipotent and eschewing all forms of idol worship. He recognizes that uneducated Hindus worshiped a multiplicity of idols yet points out that even some Muslims (such as the Jabriyah) have adopted anthropomorphic concepts of God.