Besides being a means of property exchange, marriage was also seen - especially by the church - as a means for regulating sexual activity and controlling carnal desire. All sex outside of marriage was universally considered sinful, and for most canonists and theologians, sex within marriage was only acceptable as a means for procreation. Although most authors agreed that a good sexual relationship was beneficial to marriage, it was also popular opinion that neither desire nor pleasure should play a major role in these relationships. For example, Thomas Aquinas warned that a man who slept with his wife solely for pleasure was treating her like a prostitute (Brundage, 448). Similarly, St. Jerome stated in the fourth century that "a man who is too passionately in love with his wife is an adulterer," and this was a sentiment which remained prevalent up until the end of the sixteenth century (Richards, 23-24). William of Pagula was a bit more lenient in his view that it was not sinful to marry for sexual attraction, so long as this was not the primary reason (Brundage, 430). Consistently, procreation, or "the divine plan" of continuing the race, was seen as the only acceptable end to marital relations.

    Not only was the purpose of sex within marriage made abundantly clear by the church, but there were many rules and regulations pertaining to the act itself. According to James Brundage, "marital relations required forethought, deliberation, and conscious reflection if one wished to avoid serious sin" (450). TheSummae Confessorum, a handbook for confessors published during the early thirteenth century, listed some of the times in which sexual activity between husband and wife was not permitted, which included all feast and fast days, on Sundays, and at all times when the woman was considered "unclean" (during menstruation or pregnancy, while she was breast-feeding, and for forty days after childbirth). This meant that, on average, most married couples could legally have sex less than once a week (Richards, 28-29).

    Other times where sex was seen as unacceptable or as sodomy include but are certainly not limited to, holidays of obligation, the four Ember weeks, the eves of the Apostles and a numerous array of subsidiary Saints, Fridays and Saturdays, the Sabbath, the whole of Lent, certain phases of the moon, and various special occasions.

    In addition to prescribing when couples might have intercourse, the church also provided instructions for marital coitus. The treatise De secretis mulierum gave a detailed account of the process, advising physical and mental preparation (such as the emptying of the bowels and bladder) and sufficient foreplay, or fondling of "the lower parts," in order to raise the female's body heat to the correct temperature. When the wife began "to speak as if she were babbling," the husband should know to make his move (Brundage, 451).

    As time passed ideologies began to break down and certain acts once considered as sodomy or deviant became permissible. Albert the Great even excused sex during pregnancy, claiming that the fetus stimulated sexual desire in the woman: "A woman never desires sex so much as she does when she is pregnant... Medicine is most needed in the time of greatest illness" (Brundage, 451-2).