What did early leaders of Christianity have to say about sex?
Saint Augustine, the leading theologian of the fourth century, embraced the faith on April 25, 387 along with his "illegitimate" son, leaving behind his wife and his second mistress. He had already split up from his first concubine, the mother of his son, after 17 years of living together. He turned his home in Hippo into a monastery, and as Bishop of Hippo, proceeded to make many literary contributions to Christianity. Unfortunately, his sexual views were sadly affected by the monastic temperament of the times, perhaps an over-compensation for the sexuality of his liberal youth.
It was Saint Augustine who, according to Nigel Davies in The Rampant God, "set the final seal on the anti-sexual bias of the Church" (Davies, 1984: 180). Before becoming a Christian, Saint Augustine had studied the works of Plotinus, and for eleven years was a member of the Manichaean sect, whose founder taught that Adam and Eve resulted from the Devil's children having sex, and procreation was just another evil part of the Prince of Darkness' creation.
Saint Augustine did, however, consider sex a necessary evil, though certainly not something to be enjoyed. He even thought it was permissible to take a second wife if the first was barren, and grudgingly admitted that Adam and Eve may have had sex in the Garden before their Fall, but theorized that it was a very cold dutiful mechanical act without passion. After daring to suggest that even if they did have sex in the Garden, he assures his readers that they certainly would not have enjoyed it.
Perish the thought, that there should have been any unregulated excitement, or any [excitement so great that they would ever] need to resist desire! (Augustine c. duas epist, Pelag. I 34, 17).
The somewhat moderating stance of an earlier theologian, Saint Clement of Alexandria (c. 150 - c. 200), may have helped temper Augustine's attack on sex, or simply reflected the change in attitude towards sex that had taken place in the Church. Clement, himself a celibate monk, taught that those who condemn sex within marriage set themselves against the teachings of the Gospels, and that marriage was conducive to the spiritual well-being of faithful Christians. Though, having sex for pleasure rather than procreation, "voluptuous joy" as he called it, he discouraged  (Brundage, 1987: 66,67).
Many contemporaries of Saint Augustine were equally cool towards human coitus, and therefore cold towards women in general. Some early monastics became so anti-sex that they all but declared God an unfit Creator, who obviously should have invented a better way of dealing with the problem of procreation. Arnobius (d. c. A.D. 317) called intercourse filthy and degrading, and stated that it would be blasphemous even to imagine that Jesus was "born of vile coitus and came into the light as a result of the spewing forth of senseless semen, a product of obscene gropings" (Brundage, 1987: 64).
Methodius thought sex was "unseemly," and Ambrose, a "defilement." Saint John Chrysostom, the "golden-mouthed" orator of the fourth century, had little golden to say about the fair sex in general: "Among all savage beasts, none is found as harmful as woman."
Tertullian was so repulsed by sex he publicly renounced his own sexual relationship with his wife and taught that sexual intercourse drives out the Holy Spirit. Women, he declared, are "the devil's door: through them Satan creeps into men's hearts and minds and works his wiles for their spiritual destruction." Saint Thomas Aquinas in the thirteenth century showed little improvement in attitude, saying that "Woman is defective and accidental . . . a male gone awry . . . the result of some weakness in the father's generative power" (cited in Rice, 1990: 138). A teaching common during that time taught that women and the lower half of men were created by the Devil.
Various sex sins according to ancient Christian theologians
1. No sin is committed if the married couple have sexual intercourse without feeling pleasure. (casuistry)
It was following this precept that women, in order not to commit the sin of lust which they would have to confess, (is it possible that there are still some today?), during sexual intercourse recited: “ I am not doing it for my pleasure but to give God a son".
2. If during sexual intercourse either the husband or wife passionately desires the other, he or she commits mortal sin. (S. Geronimo – theologian).
3. Fondling preceding sexual intercourse is to be considered a venial sin if it is limited to simple caresses, but becomes a mortal sin if the mouth or genitals are kissed, especially when the tongue is inserted. (Debreyne – Theologian)
4. A husband and wife should not have sexual intercourse more than four times a month. (Sanchez – theologian).
5. It is not considered a sin if a couple has sexual intercourse during the day and it is repeated the following night. (Sant’Alfonso de Ligueri – theologian).
6. It is not considered a sin if the husband or wife withdraws from coitus before emitting semen. (This was because it was believed that the woman produced semen too). (Sanchez – Theologian)
7. As the man weakens before the woman it is considered a sin if the woman expects to have sexual intercourse twice running. (Zacchia – theologian).
8. In sexual foreplay it is considered a venial sin if the penis is inserted into the woman’s mouth or the man inserts a finger into the woman’s anus. (Ecclesiastical code).
9. A man who measures the length of his own penis commits a serious mortal sin. (Monsabrè – theologian).
10. Female masturbation is considered a venial sin if done on the external part of the vagina and a mortal sin if the fingers or any other object are inserted into the vagina. (Debrayne – theologian).
11. As lying on the back is not natural, the woman must have sexual intercourse turning her back to the man, otherwise she will commit a sin. (casuistry).
12. When a woman claims to have been raped by the Devil, a careful examination of her vagina and anus must be carried out in order to assess the effects.
To have an idea of how the inquisitors carried out these examinations on the nuns in convents when they claimed to have been raped by the devil, we can read some reports made by witnesses: “The vice of the inquisitors was evident in scandalously obscene ceremonies” (Margaret Murray). “The curiosity of the judges was insatiable; they wanted to know everything about the sexual intercourse the nuns had had with the Devil in very fine detail” (Henry Lea), which is still done today in the confessional), and Jacques Fines, a reporter of the time, wrote that he had seen the inquisitors themselves raping the nuns during their controls (The inquisitors apparently used their penises instead of their fingers to explore their vaginas).
13. So that coitus should not be considered a sin, the semen has to be deposited inside the vagina beyond the lips of the uterus. (Zacchia – theologian).
14. In order to eliminate the frigidness which was the result of the lack of erection of the penis, Sanchez believed it was necessary to hold three masses, other theologians believed that it was preferable to resort to exorcism or to the practice of the communion.
15. Anal intercourse is not considered a mortal sin if the semen is deposited in the vagina. (Sanchez – theologian).
16. Seminarists or young trainee priests only commit venial sin if they reach ejaculation through simple caresses. (Diagonali).
17. Contrarily to the involuntary pollution which does not generate guilt, masturbation must be regarded as a serious sin because it can be considered adultery, incest or rape, depending on who the person is thinking about at the time. Masturbation becomes a horrible sacrilege if the object of desire is the Virgin Mary. (Sanchez – theologian).
Now admittedly there is a trend today in some branches of Christianity toward a more liberal and free attitude toward sex, especially in marriage and the privacy of the home. My point with this "rant" is to show that for hundreds of years Christians have equated sex with sin and it is only very recently that that attitude has begun to change.
Christianity, like every other man made institution, is changing with the times, albeit slowly. Either that, or the Holy Spirit is doing a new thing, and we know that GOD never changes.