In Christianity, the doctrine that God has long ago determined who will be saved and who will be damned. Three types of predestination doctrine have developed. One doctrine holds that God singled out the saved because he foresaw their future merits. A second doctrine (often identified with John Calvin) states that from eternity God has determined the saved and the damned, regardless of their merit or lack thereof. A third doctrine, set forth by Thomas Aquinas and Martin Luther, ascribes salvation to the unmerited grace of God but links the lack of grace to sin. In Islam, issues of predestination and free will were argued extensively. The Mutazila held that God would be unjust if he predestined all human actions; the Ashariya advocated a strict predestination that became the mainstream Islamic view.