This is the seventh installment of a blog series announced here.
Ever since Walter Bauer published his now famous Orthodoxy and Heresy in Earliest Christianity there has been a widespread obsession amongst modern scholars with the theme of early Christian diversity. Study after study has explored how different, contradictory, and divergent early Christian beliefs were. And it is on this basis that the terms “heresy” and “orthodoxy” are declared to be unintelligible prior to the fourth century. After all, we are told, there was no Christianity (as we know it) prior to this time period, but only a variety of different Christianities (plural) all claiming they are the true and original version. Thus, on what basis could the earliest followers of Jesus have ever adjudicated such varied claims? How could they ever have known who was right and who was wrong? It wasn’t until the fourth century, when a particular version of Christianity “won” the theological wars and declared their books were declared to be canonical, that we really can begin to speak of heresy and orthodoxy in a meaningful way.
But is it really the case that pre-fourth century Christians had no basis or standard by which they could distinguish heresy from orthodoxy? Were they really wandering around blind without a reliable guide? There are good reasons to doubt these claims. On the contrary, we shall argue here that early Christians would have had three solid guideposts as they navigated the doctrinal complexities of their faith:
a. The Old Testament. Routinely overlooked by those in the Bauer camp—ironically in a Marcionite fashion—is the decisive role played by the Old Testament amongst the earliest Christians. M.F. Wiles once declared, “There was never a time when the Church was without written Scriptures. From the beginning she had the Old Testament and it was for her the oracles of God.” Aside from the numerous examples of Old Testament usage within the New Testament itself, quotations from the Old Testament are abundant within the writings of the apostolic fathers and other early Christian texts. Thus, right from the outset, certain “versions” of Christianity would have been ruled as out of bounds. For example, any quasi-Gnostic version of the faith which suggested the God of the Old Testament was not the true God but a “demiurge”—as in the case of the heretic Marcion—would have been deemed unorthodox on the basis of these Old Testament canonical books alone. As Ben Witherington has observed, “Gnosticism was a non-starter from the outset because it rejected the very book the earliest Christians recognized as authoritative—the Old Testament.” So, the claim that early Christians had no Scripture on which to base their declarations that some group was heretical and another orthodox is simply mistaken. The Old Testament books would have provided that initial doctrinal foundation.
b. “Core” New Testament Books. Although all New Testament books are orthodox, not all of them needed to have this expressly established prior to their recognition by the early church (or at least portions thereof). As we discussed in a prior blog post, some New Testament books, especially Paul’s major epistles and the four gospels, would have been recognized as authoritative from a very early time period. They were received not so much because they measured up to some standard of orthodoxy but primarily on the basis of their obvious apostolic origins—these were the books that were “handed down” from the apostles. Gamble notes, “The letters of Paul and the Synoptic Gospels…had been valued so long and so widely that their orthodoxy could only be taken for granted: it would have been nonsensical for the church to have inquired, for example, into the orthodoxy of Paul!” Thus, there appears to have been a collection of core New Testament writings that would have functioned as a norm for apostolic doctrine at quite an early point. This explains why the vast majority of later “disagreements” about the boundaries of the New Testament canon appear to be focused narrowly on only a handful of books; apparently the core of the New Testament was intact from a very early time period.
c. The “rule of faith.” The authoritative apostolic tradition in the first century came to be summarized and known by a number of names such as the regula fidei (“rule of faith”), or “the canon of truth”). This summary was used as a key weapon in the early church’s battle against heresy by church fathers such as Dionysius of Corinth, Hipploytus, Irenaeus, Clement of Alexandria, Tertullian, and Origen. The rule of faith was a particularly effective weapon because it was oral (in a mostly illiterate world), it was relatively brief (and therefore easily employed), and it was widespread (and thus available to a broad range of churches). The rule of faith did not contain new teachings or doctrines that were not found in the Scriptures, nor was it unduly separated from the Scriptures as if they were two entirely independent sources for orthodox teaching. Instead, it was understood to be “a summary of Scripture’s own story line” or “the principle and logic of Scripture itself.” Or, as Irenaeus put it, the rule is “the order and the connection of the Scriptures.”
In sum, we can agree that the earliest Christians did not have a completed New Testament canon from the start. It took time for this to fully develop. However, this does not mean that early Christians were drifting aimlessly in the theological ocean of the first few centuries. They had the Old Testament, the earliest “core” of the New Testament, and the rule of faith to guide them.
 M.F. Wiles, “Origen as Biblical Scholar,” in The Cambridge History of the Bible: From the Beginnings to Jerome (ed. P.R. Ackroyd and C.F. Evans; Cambridge: Cambridge University Press, 1993), 454.
 Ben Witherington, The Gospel Code: Novel Claims About Jesus, Mary Magadelene, and Da Vinci (Downers Grove: InterVarsity, 2004), 115.
 Gamble, The New Testament Canon, 70.
 Vanhoozer, The Drama Of Doctrine, 206.
 John J. O’Keefe and R. R. Reno, Sanctified Vision: An Introduction to Early Christian Interpretation of the Bible (Baltimore: The Johns Hopkins University Press, 2005), 120.
 Haer 1.8.1.