The Zoroastrian scripture is a book known as the Vestal. From latter texts we know that only about a quarter of the original has survived. The surviving portion is concerned with priestly rituals and is believed to be spiritually powerful and authoritative.

Inevitably, in a religion as old as this one, there are many shades of belief and various interpretations of the faith. There are orthodox and reform groups who interpret the tradition differently, with some emphasizing the mythology and others not.

In India some Parsis have been influenced by Hindu beliefs regarding rebirth, an influence not felt in Iran. In the western Diaspora there is a greater emphasis on understanding the meaning of prayers and knowing the doctrinal teachings, whereas in India the emphasis is on identity and being a member of the community rather than on teachings. There are, of course, exceptions to this, most notably a movement called ‘Zoroastrian Studies’ led by an Oxford graduate based in Mumbai. However, the core teachings supporting the myths of creation and the end of time (Frashegird), the conflict between good and evil, care for the world, and the belief that one will be judged by the balance of good and evil thoughts, words and deeds, have continued to hold firm.

All the leading figures who followed Zoroaster in ancient and modern times have claimed only to interpret the poetic hymns of the prophet. His teaching is seen as showing the path of Righteousness to Heaven (called the House of Song).