" The angel’s nature then is rational, and intelligent, and endowed with free-will, change. able in will, or fickle. For all that is created is changeable, and only that which is un-created is unchangeable. Also all that is rational is endowed with free-will. As it is, then, rational and intelligent, it is endowed with free-will: and as it is created, it is changeable, having power either to abide or progress in goodness, or to turn towards evil. "

― John of Damascus , An Exact Exposition of the Orthodox Faith