City of God

But whether Venus could bear Æneas to a human father Anchises, or Mars beget Romulus of the daughter of Numitor, we leave as unsettled questions. For our own Scriptures suggest the very similar question, whether the fallen angels had sexual intercourse with the daughters of men, by which the earth was at that time filled with giants, that is, with enormously large and strong men. At present, then, I will limit my discussion to this dilemma: If that which their books relate about the mother of Æneas and the father of Romulus be true, how can the gods be displeased with men for adulteries which, when committed by themselves, excite no displeasure?

If it is false, not even in this case can the gods be angry that men should really commit adulteries, which, even when falsely attributed to the gods, they delight in. Moreover, if the adultery of Mars be discredited, that Venus also may be freed from the imputation, then the mother of Romulus is left unshielded by the pretext of a divine seduction. For Sylvia was a vestal priestess, and the gods ought to avenge this sacrilege on the Romans with greater severity than Paris' adultery on the Trojans.

For even the Romans themselves in primitive times used to go so far as to bury alive any vestal who was detected in adultery, while women unconsecrated, though they were punished, were never punished with death for that crime; and thus they more earnestly vindicated the purity of shrines they esteemed divine, than of the human bed.