3 Augustine replied: As to Enoch and Elias and Moses, our belief is determined not by Faustus' suppositions, but by the declarations of Scripture, resting as they do on foundations of the strongest and surest evidence. People in error, as you are, are unfit to decide what is natural, and what contrary to nature. We admit that what is contrary to the ordinary course of human experience is commonly spoken of as contrary to nature. Thus the apostle uses the words, "If you are cut out of the wild olive, and engrafted contrary to nature in the good olive." Contrary to nature is here used in the sense of contrary to human experience of the course of nature; as that a wild olive engrafted in a good olive should bring forth the fatness of the olive instead of wild berries.
But God, the Author and Creator of all natures, does nothing contrary to nature; for whatever is done by Him who appoints all natural order and measure and proportion must be natural in every case. And man himself acts contrary to nature only when he sins; and then by punishment he is brought back to nature again. The natural order of justice requires either that sin should not be committed or that it should not go unpunished. In either case, the natural order is preserved, if not by the soul, at least by God.
For sin pains the conscience, and brings grief on the mind of the sinner, by the loss of the light of justice, even should no physical sufferings follow, which are inflicted for correction, or are reserved for the incorrigible. There is, however, no impropriety in saying that God does a thing contrary to nature, when it is contrary to what we know of nature. For we give the name nature to the usual common course of nature; and whatever God does contrary to this, we call a prodigy, or a miracle.
But against the supreme law of nature, which is beyond the knowledge both of the ungodly and of weak believers, God never acts, any more than He acts against Himself. As regards spiritual and rational beings, to which class the human soul belongs, the more they partake of this unchangeable law and light, the more clearly they see what is possible, and what impossible; and again, the greater their distance from it, the less their perception of the future, and the more frequent their surprise at strange occurrences.
Source: Reply to Faustus the Manichaean (New Advent)