Michael J. Kruger is professor of New Testament at Reformed Theological Seminary in Charlotte, 2012). He blogs regularly at Canon Fodder. In an article at The Gospel Coalition he writes:

Skeptics commonly criticize core Christian beliefs by claiming that they were not really held by the earliest Christians. Instead, we are told, these beliefs were invented post facto by the institutional church.

The classic example of such an argument has to do with the divinity of Jesus. The earliest followers of Jesus didn’t really believe that Jesus was divine, this argument goes; it was only the later institutional church, under political pressure from Emperor Constantine, that insisted Jesus must have divine status. Thus, some argue, the belief that Jesus is God is not really, well, Christian.

Substitutionary Atonement

This same sort of argument has also been applied to other doctrines, particularly the substitutionary nature of the atonement. Critical scholars, led by the classic work of Gustaf Aulén, have long argued that the earliest Christians did not believe that Christ died as a substitute for sinners. Instead, they say, these Christians believed what is known as the “Christus victor” view of the atonement—the idea that Jesus’s death on the cross (and resurrection) conquered the Devil and other forces that held people in bondage. On this view, Christ did not die in place of rebellious sinners but instead rescued victims from a fallen world.

If Aulén is correct, then when did the substitutionary view of the atonement arise? Peter Carnley embodies the typical critical approach when he says that the substitutionary view “was not known before Anselm’s time.” Thus, Carnley claims, it was not until the Middle Ages, when Anselm wrote Cur Deus Homo (Why the God-Man?), that Christians began to believe Christ died in place of sinners.

No doubt these sorts of scholarly arguments can explain why alternative theories of the atonement have gained popularity in recent years, while the substitutionary view continues to be vilified as un-Christian. Rob Bell does precisely this in his book Love Wins, where he roundly rejects the substitutionary view in favor of other options.

But is it really true that the substitutionary view of the atonement was not found before the Middle Ages? Not at all. Such a claim can be readily refuted merely by examining the writings of the New Testament itself—particularly the letters of Paul. However, it is also worth noting that key elements of the substitutionary view were held by some of the earliest Christian writers. One example is the author of the Epistle to Diognetus from the early second century. The Epistle to Diognetus was written by an unknown Greek author as an apology for Christianity. Below are some excerpts from the author that affirm key aspects of substitutionary atonement.

Seriousness of Sin

The author writes:

And when we had demonstrated that we were powerless to enter the kingdom of God on our own, were were enabled by the power of God. For our unrighteous way of life came to fruition and it became perfectly clear that it could expect only punishment and death as its ultimate reward. (9.1-2)

Here is a clear affirmation of human inability to save ourselves (akin to total depravity), and a full acknowledgement that sin deserves the ultimate penalty of death.

Grace and Love of God

God demonstrated his love for sinners through his atoning death. The author writes:

But then, when the time arrived that God planned to reveal at last his goodness and power (Oh the supreme beneficence and love of God!), he did not hate us, destroy us, or hold a grudge against us. (9.2)

God’s response to our sin, though deserving of death, is not to bring judgment but to show mercy. Notice that the author is amazed by God’s mercy. The author recognizes that God’s natural response, due to his holiness, would be to destroy sinful people.

Christ Bore Our Sins on Himself

Here is where we get to the crux of substitutionary atonement:

But [God] was patient, he bore with us, and out of pity for us took our sins upon himself. He gave up his own Son as a ransom for us, the holy one for the lawless, the innocent one for the wicked, the righteous one for the unrighteous, the imperishable one for the perishable, the immortal one for the mortal. (9.2)

This is a remarkable passage. Undoubtedly, the author views the work of Christ on the cross as an exchange of the righteous for the unrighteous, that we might be saved; Christ is a substitute.

Even more the author says, “God took our sins upon himself.” Presumably the author has God the Son in view here, or is simply saying that God (in Christ) took sins upon himself. Either way, the phrase “upon himself” certainly suggests bearing sin. This is confirmed in the fact that Jesus is described as a “ransom,” a payment of some sort. His work on the cross pays some debt.

And notice the personal language: “our sins.” Jesus did not just die for a cause, or for an idea, but for individuals.

This entire combination suggests that Jesus took the sins of individuals upon himself as a payment. A payment for what? Given the author’s earlier statement that we deserve “punishment” from God for our sins, it seems reasonable to conclude that Jesus paid this penalty we deserve. He satisfies the justice of God that would otherwise fall upon us.

Christ’s Righteousness Covers Us

Incredibly, the author of the Epistle to Diognetus even seems to affirm what Reformed theologians refer to as the doctrine of imputation. This doctrine says that our justification is not only about having our sins taken away, but also having Christ’s positive righteousness cover us.

This doctrine has also come under attack in recent years. Some scholars have suggested that the Reformed view of justification, which includes a robust understanding of imputation, was largely invented by the Reformers in their overreaction to Rome.

There is not space to respond fully to such claims here. But the author of the Epistle to Diognetus articulates a view that sounds close to the Reformed understanding of imputation:

For what else could hide our sins but the righteousness of that one? How could we who were lawless and impious be made upright except by the son of God alone? Oh the sweet exchange! . . . That the lawless deeds of many should be hidden by the one who was upright, and the righteousness of one should make upright the many who were lawless! (9.3-5)

This is a significant passage because it doesn’t dwell merely on our sins being taken away, but deals substantively and primarily with the righteousness of Christ. And what does that righteousness do? It hides our sins. It “makes upright” the lawless. And this happens in a “sweet exchange.” If we are looking for an ancient writer who describes the doctrine of the imputation of Christ’s righteousness, this author comes awfully close.

The Epistle to Diognetus shows that the doctrine of the substitutionary atonement and the imputation of Christ’s righteousness are not wholesale inventions of later Christians, but were present, at least in seed form, early in the history of Christianity. Did some Christian groups hold other views of such matters? Sure. But the continuity between the teachings of this epistle and the writings of Paul himself (see especially Romans 5) make it evident that the substitutionary atonement/imputation view goes back very early indeed.