Wherefore the devil holds infants guilty who are born, not of the good by which marriage is good, but of the evil of concupiscence, which, indeed, marriage uses aright, but at which even marriage has occasion to feel shame…Now from this concupiscence whatever comes into being by natural birth is bound by original sin, unless, indeed, it be born again in Him whom the Virgin conceived without this concupiscence. Wherefore, when He vouchsafed to be born in the flesh, He alone was born without sin. – On Marriage and Concupiscence 1:27