Chapter 30. Prescience and Predestination. (Book 2. The created world, and man's faculties and potential) (On the Orthodox Faith) (Damascene, John)

We ought to understand that while God knows all things beforehand, yet he does not predetermine all things. For he knows beforehand those things that are in our power, but he does not predetermine them. For it is not his will that there should be wickedness nor does he choose to compel virtue. So that predeconclusion is the work of the divine command based on fore-knowledge. But on the other hand God predetermines those things which are not within our power in accordance with his prescience. For already God in his prescience has prejudged all things in accordance with his goodness and justice.

Bear in mind, too, that virtue is a gift from God implanted in our nature, and that he himself is the source and cause of all good, and without his co-operation and help we cannot will or do any good thing, But we have it in our power either to abide in virtue and follow God, who calls us into ways of virtue, or to stray from paths of virtue, which is to dwell in wickedness, and to follow the devil who summons but cannot compel us. For wickedness is nothing else than the withdrawal of goodness, just as darkness is nothing else than the withdrawal of light While then we abide in the natural state we abide in virtue, but when we deviate from the natural state, that is from virtue, we come into an unnatural state and dwell in wickedness.