De Principiis

²² But since the apostle in one place does not pretend that the becoming of a vessel unto honour or dishonour depends upon God, but refers back the whole to ourselves, saying, “If, then, a man purge himself, he will be a vessel unto honour, sanctified, meet for the Master's use, and prepared unto every good work;” and elsewhere does not even pretend that it is dependent upon ourselves, but appears to attribute the whole to God, saying, “The potter has power over the clay, of the same lump to make one vessel unto honour and another to dishonour;” and as his statements are not contradictory, we must reconcile them, and extract one complete statement from both.

Neither does our own power, apart from the knowledge of God, compel us to make progress; nor does the knowledge of God (do so), unless we ourselves also contribute something to the good result; nor does our own power, apart from the knowledge of God, and the use of the power that worthily belongs to us, make a man become (a vessel) unto honour or dishonour; nor does the will of God alone form a man to honour or to dishonour, unless He hold our will to be a kind of matter that admits of variation, and that inclines to a better or worse course of conduct. And these observations are sufficient to have been made by us on the subject of free-will.