It was during the last quarter of the second century in the eastern Mediterranean, possibly in the city of Alexandria, that a man by the name of Diognetus met a Christian author as well as some other believers. It is not surprising that as Diognetus spent time with this man and the others, he began to ask them questions: What do you Christians believe about God? Why do you reject the gods that other Greeks and Romans worship? Why do you Christians use the Jewish Old Testament even though you’re not Jews? And Diognetus was amazed when he saw the way these Christians related to one another, for it was evident that they loved each other like people in the same family were to love each other. Why was that?
Simple though these questions might seem, they actually touch on utterly central matters: Who is the God that Christians worship, and what difference does this worship make for daily life? A number of discussions about these subjects ensued, and it became very evident that Diognetus was earnest about knowing the Truth. The Christian author decided, therefore, to write to his unbelieving friend and explain in a fairly succinct form what Christians think about these matters.
The resulting letter, which historians now call The Letter to Diognetus, is a veritable gem of early Christian apologetics. Beyond the fact that the author obviously benefited from a superb education and that he knew portions of the New Testament extremely well, scholars have no real idea as to who wrote this letter.
In the World, but Not of the World
The author of the letter notes that, unlike the Jews, Christians are not to be distinguished from their fellow Greeks and Romans by virtue of their geographical locale, distinct language, or various unique customs of dress, food, and other matters of daily life. When it comes to all of these things, they lived like the other citizens of the Roman Empire. Yet, their Christian commitment did draw certain lines of demarcation between themselves and their surrounding culture:
They live in their own native lands, but as sojourners; they share all things as citizens, and endure everything as foreigners. . . . They marry, like everyone else, have children, but they do not expose their infants. They share a common table, but not the marriage bed. They are in the flesh, but do not live according to the flesh. They spend [their days] on earth, but their citizenship is in heaven. (Letter to Diognetus 5.5–9)
Here the New Testament language of sojourning and heavenly citizenship is pressed into service to affirm the paradox of Christian existence. The Christian life is one that was similar in so many ways to the mores of Greco-Roman society, but in certain key areas—notably with regard to the treatment of children and sexual expression—it bore witness to a completely different ethic.
On Abortion and Sexual Immorality
Although abortion did take place in Greek and Roman culture, it was not a common solution for unwanted children, since it posed a huge danger to the life of the mother. Hence, the preferred method to solve the problem of unwanted progeny was to leave them in the street after birth. There, they would die of exposure or be picked up by slave traders or brothel owners—or thankfully, in some cases, babies were picked up by Christians and raised in believing households. Greeks and Romans saw nothing wrong with the practice of exposure, but Christians rightly knew that such an ethical stance was tantamount to murder.
The other key area in which these Christians differed from their culture was with regard to sexual expression. Many Greco-Roman pagans saw nothing wrong with casual sex with those who were not their spouses—the use of slaves in this way was extremely common. But this was not the Christian way. The church was not hesitant to affirm the goodness of sex, but it had boundaries—namely, marriage between a husband and wife.
The Ground of the Christian Ethic
Further on in the letter, the anonymous author grounds these vital ethical perspectives in the cross. The letter says:
[God] himself gave his own Son as a ransom for us—the Holy One for the godless, the Innocent One for the wicked, the Righteous One for the unrighteous, the Incorruptible for the corruptible, the Immortal for the mortal. For what else was able to cover our sins except his righteousness? In whom could we, who were lawless and godless, have been justified, but in the Son of God alone? O the sweet exchange! O the inscrutable work of God! O blessings beyond all expectation!—that the wickedness of many should be hidden in the one Righteous Man, and the righteousness of the One should justify the many wicked! (Diognetus 9.2–5)
The author is overwhelmed by what took place at the cross—lost in rapture, awe, and praise, as Charles Wesley might put it.
This is why Christians live lives of sexual purity: having experienced God’s holy love for them, they can do nothing else but “imitate his [i.e., God’s] goodness” (Diognetus 10.3). Though wholly counter-cultural in its day, this expression of sexual purity won many to Christ. May it do so again.