Nicene and Post-Nicene Fathers, Vol. II:
City of God: Chapter 18

Chapter 18.—Of the Shame Which Attends All Sexual Intercourse.

Lust requires for its consummation darkness and secrecy; and this not only when un p. 277 lawful intercourse is desired, but even such fornication as the earthly city has legalized.  Where there is no fear of punishment, these permitted pleasures still shrink from the public eye.  Even where provision is made for this lust, secrecy also is provided; and while lust found it easy to remove the prohibitions of law, shamelessness found it impossible to lay aside the veil of retirement.  For even shameless men call this shameful; and though they love the pleasure, dare not display it.  What! does not even conjugal intercourse, sanctioned as it is by law for the propagation of children, legitimate and honorable though it be, does it not seek retirement from every eye?  Before the bridegroom fondles his bride, does he not exclude the attendants, and even the paranymphs, and such friends as the closest ties have admitted to the bridal chamber?  The greatest master of Roman eloquence says, that all right actions wish to be set in the light, i.e., desire to be known.  This right action, however, has such a desire to be known, that yet it blushes to be seen.  Who does not know what passes between husband and wife that children may be born?  Is it not for this purpose that wives are married with such ceremony?  And yet, when this well-understood act is gone about for the procreation of children, not even the children themselves, who may already have been born to them, are suffered to be witnesses.  This right action seeks the light, in so far as it seeks to be known, but yet dreads being seen.  And why so, if not because that which is by nature fitting and decent is so done as to be accompanied with a shame-begetting penalty of sin?