The holy book of the Zoroastrians is the called the Avesta. It includes the original words of the founder, Zarathushtra, preserved in a series of five hymns, called the Gathas. The Gathas are abstract poetry, directed towards the worshiop of one god, the understanding of cosmic orderm, and the promotion of social justice and individual goals between good and evil. At a later date the remaining parts of the Avesta were written down. Which deal with laws of ritual and practice.