Not a single church father can be found who did not assume that Christians should remain chaste before marriage.

In the early second century, the Roman governor Pliny questioned some ex-Christians, who reported that Christians met before dawn for a secret ritual that included an oath to refrain from moral no-nos, including sexual sins. The ritual so described is generally considered to have been baptism, which, as Justin Martyr described a few years later, did require the new Christian to make this kind of moral promise.

Turning to such early church manuals as the Didache, Clement of Alexandria's Paidagogos, or the many disciplinary writings of Tertullian, we find sexual sins getting a lot of attention. Fornication (sex between unmarried people) and adultery (sex by married people with other partners) are condemned in the strongest terms, and discussions keep cropping up about whether newly baptized Christians should be required—or at least urged—to remain celibate, and about whether sex in marriage should be only for the purpose of conceiving children.

Reading these discussions, you get the sense that "the sky hung low" for these people. That is, heaven was a nearby, almost tangible reality, where many natural physical functions would drop away into insignificance: no one would be married (Luke 20:34-36), be born, or die. In a church vividly aware that this was the place of which they were truly citizens, it was not a stretch to say that even God's command in Genesis to "be fruitful and multiply" was now suspended—at least, for those carrying the good news of Christ's gospel to a world next door to death. Such messengers of heaven saw themselves as strangers and sojourners in a transitory, sin-besotted physical world. The anticipation of heaven was so powerful that it motivated some to begin living as the angels do—renouncing such physical pleasures as sexual intercourse.

This heavenly-mindedness may help account for the fact that chastity—or "virginity" as the early Christians often called it—became a hallmark of spiritual greatness among the Christians. Neither the Jews nor the pagans had ever much linked spiritual perfection with sexual abstention.

Another (but probably less influential) reason "virginity" became the badge of honor for many early Christians was that some of their Roman persecutors, in their attempts to give Christianity a bad name, accused the Christians of engaging in secret sex rituals in their meetings. As the second-century defender of the faith Justin Martyr wrote:

Either we do not marry except to rear children, or we refuse to marry and we exercise complete self-control. Further, to convince you that we do not have a secret rite or licentious sexual intercourse, one of us sent to Felix, the governor of Alexandria, asking him to permit a surgeon to take away his [the Christian's] testicles. For the surgeons there said that they were forbidden to do this without the permission of the governor. When Felix was not at all willing to sign [this permission], the youth remained by himself, and found his own and his associates' conscience sufficient (First Apology, 29).

In fact, the brilliant exegete Origen did have himself castrated. He wrote, "God has allowed us to marry wives, because not everyone is capable of the superior condition, which is to be absolutely pure" (Against Celsus, 8:55).

There was another source, beyond heavenly-mindedness and defensive agendas, for such extreme practices and related teachings. This was the teaching of the Gnostic heretics. Gnostics considered the body—and indeed all matter—to be evil, created by a "demiurge" and not the good, redemptive God represented in Jesus. They therefore mandated total celibacy for their disciples.

The early church father Clement of Alexandria was one of many who struggled against these Gnostics. He attacked a book by the Gnostic teacher Julius Cassianus, Concerning Self-Control or Concerning Eunuchry. Cassianus argued, "Let no one say that, since we have these parts so that the female body is arranged this way and the male that way, the one to receive, the other to implant, sexual intercourse is allowed by God. For if this equipment was from the God toward whom we hasten, he would not have said that eunuchs are blessed." He concluded that Jesus had come to "reform us and free us from error and from the intercourse of these appended and shameful parts." Such teachers, said Clement, "with words fair-sounding through self-control commit sacrilege against both the creation and the holy Creator" (Clement of Alexandria, Miscellanies 3.91-92, 3.45).

Clement and the other fathers followed the apostle Paul in counseling against such extreme sexual self-denial. Paul was well aware of the strong pull of human sexual desire and its tendency to lead fallible humans into immorality. In his first letter to the Corinthians, he responded to their slogan, "It is good for a man not to marry," by insisting that, though this might be good for those with the gift of celibacy, like himself, heroic chastity might easily provide opportunity for the devil. To "the unmarried and the widows," he said, "if they cannot control themselves, they should marry, for it is better to marry than to burn with passion" (1 Cor. 7:8-9).

Paul's healthy respect for the human sex drive is reflected in his advice to married couples: "Do not deprive each other except by mutual consent and for a time, so that you may devote yourselves to prayer." Why such carefulness? Paul returns, in the following sentence, to the primary theme of this whole passage—the difficulty we humans have in keeping our sexual actions within godly boundaries: "Then come together again so that Satan will not tempt you because of your lack of self-control" (1 Cor. 7:1-5).

Virtually all the church fathers affirmed marriage as a good (1 Tim. 4:3) and found at least some kind words to say about sexual intercourse within marriage. In this they joined the Jewish religious teachers, who praised marriage, repeating (from their male-centered perspective) the traditional saying "He who has no wife lives without joy, blessing, or good." But all considered premarital and extramarital sex immoral.