Ashʿariyyah, in Islam, school of theology supporting the use of reason and speculative theology (kalām) to defend the faith. Followers of the school, which was founded by Abū al-Ḥasan al-Ashʿarī in the 10th century, attempted to demonstrate the existence and nature of God (Allāh) through rational argument while affirming the eternal, uncreated nature of the Qurʾān, the sacred scripture of Islam that Muslims believe to be the divine word. They were accused by the Muʿtazilah—theologians from a school promoting a much more extreme rationalism—of believing in predestination because of their claim that the human capacity for action was acquired only at the very moment of action.