The sexual ethic of the second-century Roman Empire bears some semblance to today’s sexual revolutionary era. Sexual promiscuity (especially among men), which included not only heterosexual and homosexual acts, but also pederasty, was considered a societal good. With very few limiting principles, Roman culture encouraged this pursuit of (mostly male) sexual pleasure.
Today, nearly every aspect of our culture is sexualized. Whereas ancient public spaces were filled with sexual images, today we encounter them on television (or streaming), on the internet, and often in public spaces (try going to a shopping mall without seeing them). While Hollywood deserves credit for being the most persuasive purveyor of today’s secular ethic, America’s new sexual religion pervades its educational institutions, public libraries, sports, and the market. And with the exception of consent, little to no limiting principles constrain modern sexual practices.
As Western culture’s sexual ethic regresses into the forms of paganism known in the second century, the church finds itself with an opportunity once again to bear a powerful, counter-cultural witness. Record of the early church’s counter-cultural witness has been preserved in an anonymous letter written by an unknown Christian apologist to an unknown person named Diogentus.
The letter to Diognetus is one of the earliest works of Christian apologetics. This ancient defense of Christianity contrasts Christian belief and worship with Graeco-Roman polytheism and Judaism. It conveys a stirring image of the Christian way of life in the face of hostility and explains the origins of Christianity with the appearance of Christ,inviting its recipient, Diognetus, to believe and experience the joy of life in communion with God.
Similar, Yet Different
In the course of the letter, the Apologist who wrote this historical letter to Diognetus seeks to distinguish Christians from its Pagan and Jewish neighbors. What was it that made them different? To truly understand these differences, the Apologist elegantly explains the ways in which Christians lived similarly to their neighbors. Thus, while it was apparent that Christians held drastically different religious beliefs, the Apologist explains that despite these differences, Christians embodied ordinary life the same as everyone else. Christians thus
neither inhabit cities of their own, nor employ a peculiar form of speech, nor lead a life which is marked out by any singularity. The course of conduct which they follow has not been devised by any speculation or deliberation of inquisitive men; nor do they, like some, proclaim themselves the advocates of any merely human doctrines. But, inhabiting Greek as well as barbarian cities, according as the lot of each of them has determined, and following the customs of the natives in respect to clothing, food, and the rest of their ordinary conduct, they display to us their wonderful and confessedly striking method of life.
Christians lived in the same cities, towns, and villages as the pagan. They spoke the same language. They did not—and could not—live obscurely with respect to the basics of life. As Wayne Meeks asserts, “the daily practice of most church members was doubtless indistinguishable in most respects from that of their unconverted neighbors.” Thus, they ate the food harvested and prepared in their region; they wore clothes reflective of their culture; they went to work alongside their neighbors; they married and had children. And, as Smith argues, “how could it have been otherwise? A person who heard and believed the message about Jesus naturally continued to speak the same language as before — Greek or Latin or whatever—and to work and dress and eat in much the same ways as she had always done.”
Yet, as the Apologist conveys to Diognetus, it was by this “ordinary conduct” that Christians stood out:
They dwell in their own countries, but simply as sojourners. As citizens, they share in all things with others, and yet endure all things as if foreigners. Every foreign land is to them as their native country, and every land of their birth as a land of strangers.
Christians were good citizens and cared for their countries, yet they knew their earthly country—wherever it was—did not constitute their final home. These Christians, while living and seeking the welfare of their city, sought after the city of God.
While living in the city of man yet longing for the city of God, one of the ways Christians set themselves apart was by their sexual ethic:
They marry, as do all [others]; they beget children; but they do not destroy their offspring. They have a common table, but not a common bed. They are in the flesh, but they do not live after the flesh.
Christians married and bore children like their religious counterparts, but they did not leave their children exposed to die. In other words, they opposed the common Graeco-Roman practice of child exposure—the ancient version of today’s abortion. Whereas in the second-century, unwanted children were killed by exposure, today’s unwanted children are killed mostly —and not without dark irony — in medical facilities. The means are different, yet the outcome is the same. Today’s Christian pro-life movement is merely a continuation of the early church’s biblical ethic to protect the life of children.
The Apologist’s next phrase is noteworthy: “They have a common table, but not a common bed.” Christians, according to the Apologist, were openhanded and hospitable. They willingly shared their goods with one another (cf. Acts 2:44–46; 4:32). But, importantly, they did not share their beds. In other words, they honored God’s gift of sex in its God-designed context: marriage.
It is no surprise that the early church’s counter-cultural witness follows that outlined by Paul:
Do you not know that your bodies are members of Christ? Shall I then take the members of Christ and make them members of a prostitute? Never! Or do you not know that he who is joined to a prostitute becomes one body with her? For, as it is written, “The two will become one flesh.” But he who is joined to the Lord becomes one spirit with him. Flee from sexual immorality. Every other sin a person commits is outside the body, but the sexually immoral person sins against his own body. Or do you not know that your body is a temple of the Holy Spirit within you, whom you have from God? You are not your own, for you were bought with a price. So glorify God in your body. (1 Cor. 6:15–20, ESV)
We should not downplay the counter-cultural nature of the Christian sexual ethic. As Steven D. Smith writes in Pagans and Christians in the City, “This conception expressed a Christian ideal of purity—of the body as a temple of the Holy Spirit—that pagans found almost incomprehensible.” And so it is today.
A True Counterculture
While Western Christians formerly lived amidst cultures that broadly shared their sexual ethic, that state of affairs is gone. Today, the church is again confronted with a competing sexuality, one complete with religious zeal and moral sanction. Yesteryear’s Graeco-Roman gods of the Roman city-state have merely been displaced by the gods of the authentic self. The Christian, however, has been called to deny himself, pick up his cross, and follow the way of Jesus (Matt 16:24).
Whether the issue is abortion, divorce, cohabitation, marital infidelity, homosexuality, so-called same-sex marriage, or the legion (pun intended) of issues associated with gender ideology, the church today has the opportunity to present itself once again as a true counterculture. And Christians should seize this opportunity to communicate and demonstrate the fullness of the gospel as a better, richer, fuller, more satisfying way of life — one that honors God by honoring our bodies, our created design, and one another as men and women created in God’s image. This may not be the counterculture of best-selling books, well-paid speaking engagements, or status-affirming columns for leading newspapers, but it is one that can truly reveal the glory of Christ to the world and save many from their sins and suffering.
As our post-Christian society grows in its antagonism towards Christianity, and specifically its sexual ethic, we would do well to remember the Christian way of life described to Diognetus. Let’s pray that the future of Christianity in the West would be characterized by hospitality to our neighbors: “they have a common table” — but not sexual libertinism: “but not a common bed.” In our super-charged sexual age of digital isolation, the church should re-establish itself as a true counterculture marked by hospitality and faithfulness to the biblical sexual ethic.
Jonathan E. Swan is Managing Editor of Eikon.
 For a helpful introduction to this letter, see: Michael A.G. Haykin, Rediscovering the Church Fathers: Who They Were and How They Shaped the Church (Wheaton, IL: Crossway, 2011), 49–67. The letter can be read for free online: https://www.ccel.org/ccel/richardson/fathers.x.i.ii.html.
 “The Epistle of Mathetes to Diognetus,” in Ante-Nicene Fathers: The Writings of the Fathers Down to A.D. 325, vol. 1, The Apostolic Fathers, Justin Martyr, Irenaeus, ed. Alexander Roberts, James Donaldson, and A. Cleveland Coxe (Grand Rapids, MI: Eerdmans, 1956), 26. Hereafter referred to as “The Epistle to Diognetus.”
 Wayne A. Meeks, The Origins of Christian Morality: The First Two Centuries (New Haven: Yale University Press, 1993), 2, quoted in Steven D. Smith, Pagans and Christians in the City: Culture Wars from the Tiber to the Potomac (Grand Rapids, MI: Eerdmans, 2018), 107.
 Smith, Pagans and Christians in the City, 107.
 “The Epistle to Diognetus,” 26.
 “The Epistle to Diognetus,” 26–27.
 Steven D. Smith, Pagans and Christians in the City, 284.
 Kate Cohen, “Why are we so tolerant of churchy bigotry?” Washington Post, March 6, 2023, accessed June 1, 2023, https://www.washingtonpost.com/opinions/2023/03/06/religious-bigotry-lgbtq-homophobia/.
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