The Conferences Of John Cassian by John Cassian
Chapter IV. An objection, asking how the Gentiles can be said to have chastity without the grace of God.
Germanus: To this explanation, the excellence of which we cannot hastily disprove, it seems a difficulty that it tends to destroy free will. For as we see that many of the heathen to whom the assistance of Divine grace has certainly not been vouchsafed, are eminent not only in the virtues of frugality and patience, but (which is more remarkable) in that of chastity, how can we think that the freedom of their will is taken captive and that these virtues are granted to them by God's gift, especially as in following after the wisdom of this world, and in their utter ignorance not only of God's grace but even of the existence of the true God, as we have known Him by the course of our reading and the teaching of others -- they are said to have gained the most perfect purity of chastity by their own efforts and exertions.