Augustine of Hippo, Against Two Letters of the Pelagians IV.5: What is the Special Advantage in the Pelagian Opinions?

What advantage, then, is it to them that they say “that all sin descends not from nature, but from the will,” and resist by the truth of this judgment the Manicheans, who say that evil nature is the cause of sin; when by being unwilling to admit original sin although itself also descends from the will of the first man, they make infants to depart in guilt from the body? What advantage is it to them “that they confess that baptism is necessary for all ages,” while the Manicheans say that it is superfluous for every age, while they say that in infants it is false so far as it pertains to the forgiveness of sins? What advantage is it to them that they maintain “the flesh of Christ” (which the Manicheans contend was either no flesh at all, or a feigned flesh) to have been not only the true flesh, but also “that the soul itself was stained by no spot of sin,” when other infants are by them so put on the same level with His infancy, with not unequal purity, as that both that flesh does not appear to keep its own holiness in comparison with these, and these obtain no salvation from that?