Ibadism represents a branch of the third great division in Islam, that of the Khawarij. It survives in some isolated communities in North Africa, but manifested itself periodically in Oman as a full Imamate well into the twentieth century. Using early material recorded in Basran and Omani sources, this book deconstructs the standard account of origins, showing that Ibadism's evolution into a madhhab (school) can only be understood in a wider historical perspective of the tribal and regional dimensions. Its activation among the Yamani tribes of Iraq requires reappraising what the Yaman-Nizar division represented in the Umayyad period, and the opening chapters demonstrate that there was a real split in pre-Islamic times between northern and southern Arabs that was reflected in the great revolts of Ibn al-As'ath al-Kindi and Yazid b. al-Muhallab al-Azdi. The nascent Ibadi movement in Basra, whose solidarity was enshrined in walaya, the spiritual and physical cement binding the community to God, exploited the resulting resentment to establish Imamates in southern Arabia, followed by North Africa. Study of the earliest sources throws considerable light not only on Ibadi origins, but also the early emergence of Islamic kalam and fiqh and the influence of contemporary theological debate. The history of Ibadism in the first six Islamic centuries is essential for understanding both the evolution of institutions and practical law. One of is strengths is the ability to adapt to different situations, and the pragmatic rulings concerning agriculture, trade, mining, and in the case of Oman, its major role in expanding Indian Ocean commerce represents a unique maritime legal code. In parallel comes an increasing convergence towards Sunni-Ash'ari norms and the evolution of Ibadi identity as a madhhab. Sunna and hadith were absorbed into the athar of the community, which now develops as a formal line of transmission and even the production of their own hadith collection in the Maghrib. Nevertheless, interpretation still remained essentially open, thus giving the system a flexibility that ensured survival in widely different environments.