Bear in mind, too Cf. Clem. Alex., Strom., bk. vi.; Jerome, on Ep. ad Gal., ch. 1; Greg. Naz, Carmen de virt. hum., 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 Cf. Clem. Alex., Quis dives salvetur; Greg. Naz., Orat. 31; Chrysost., Hom. 45in Joann., Hom. in Ep. ad Hebr. xii. 2, Hom. 15 in Ep. ad Rom.; Cyril, De ador. in Spir. et ver., p. 25; Petavius, Dogm., vol. i., bk. ix. c. 4, &c. 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 Cf. infra, bk. iii. ch. 14..