Scholars argue between using Islamic and Arabic. Some say that the civilization was Islamic because the religion of Islam brought together the various peoples—mainly Arabs, Persians, and Turks—who took part in it. Because of the Arab conquests, the early Muslims picked up many concepts and institutions from Roman and Persian law. Ever mindful of the impending Judgment Day, Muslims wish to know and obey the rules of behavior that will please God and maintain a harmonious society. Some differences do exist between Shi'ite and Sunni Muslims regarding the authenticity of certain statements by the Prophet, notably one concerning whether he wanted 'Ali as his successor. By the time the 'Abbasids took power in 750, Muslims were studying the meaning of the Qur'an, the life of Muhammad, and the words and deeds ascribed to him by those who had known him. Thus evolved a specifically Islamic science of right versus wrong, or jurisprudence.