In Islamic philosophy, the processes of systematic theology, or more widely the general tradition of commentary and interpretation of Islamic doctrine, which may include adducing philosophy to support elements of religious doctrine. Sometimes (as with the opposition between al-Ghazali and Avicenna) the relationship to philosophical reason could be fairly hostile. Kalam played the role in Islam roughly parallel to that which scholastic philosophy played in the development of Christian theology, from around the time of al-Kindi onwards. The practitioners of kalam were known as the Mutakallimun. Early mutakallimun included the Mutazilites (‘those who withdraw themselves’) of the eighth century.