The role of the caliph and the learned classes in defining what Islam was to stand for, both theologically and politically, is a central theme in understanding the development of the Islamic empire itself. The basic elements of Islamic theology find their expression within the Quran and the sunna and are elaborated to some extent in works such as the Sira of Ibn Ishaq. The Khawarij are, in many ways, a marginal group when viewed within the overall context of Islamic history. The Murji’a adopted a conservative position, preserving the status quo. The Qadiriyya are those who discussed the issue of qadar, the preordination of events in the world by God. "Justice" for the Mu’tazila was equated with "good," such that it was not possible to conceive that God would be unjust or evil. Abu Mansur al-Maturidi was another of the tenth-century theologians whose influence at the time seems to have been significant in the emergence of Sunni Islam.