How and when the early church recognized the 27 books in our New Testament has always been a fascinating topic for people. There is innate curiosity within us about why these books were regarded as Scripture and not others.

Unfortunately, the high level of interest in the New Testament canon is often combined with a high number of misconceptions about the canon. For anyone willing to search for it, the internet is packed with myths, mistakes, and misunderstandings about how the whole process really worked.

While there is no quick cure for such misconceptions, there is one essential key that really helps clear away the cobwebs. And that key is understanding the different categories of books in early Christianity.

We tend to think there are only two categories, those books that are “in” and those books that are “out.” But, early Christians were more nuanced than than this. In fact, they divided up books into four categories. And understanding these categories will clear up a good number of the misunderstandings of the way the canon developed.

We will take our cue from the four categories laid out by the well-known fourth century historian Eusebius in Hist. eccl. 3.25.1-7:

1. Recognized Books. For Eusebius, these are the books that are universally recognized as canonical and have been for a long time. These include: the four Gospels, Acts, the epistles of Paul (including Hebrews), 1 John, 1 Peter, and Revelation (though he acknowledges the last one has some detractors). Put another way, Eusebius acknowledges that there has been a “core” canon (22 out of 27 books) in Christianity for some time.

What misconceptions does this refute? Some scholars continue to claim there was no canon until the fourth or fifth century. But the existence of this “core” of recognized books shows that is simply not the case. These books had been established for generations and there was never any meaningful dispute about them.

2. Disputed Books. These are books that have been subject to some ecclesiastical disagreement, but are still regarded as canonical because they “are nevertheless known to most” (3.25.3). Not surprisingly, these include the smaller books: James, Jude, 2 Peter, 2 & 3 John. The combination of recognized books and disputed books together form our 27-book canon.

What misconception does this refute? The category of disputed books reminds us that the boundaries of the canon were still “fuzzy” in the earliest centuries of Christianity and that it took a while for the church to reach a full consensus around these books. The canon was not dropped from heaven on golden tablets, but developed through the normal processes of history. And such processes aren’t always neat and tidy.

3. Rejected Books. When Eusebius uses the term “rejected” he doesn’t mean these books are heretical (that category is below), he simply means that these books are rejected in terms of having canonical status. Thus, these are books that are regarded as (generally) orthodox, helpful and useful but still did not have the authority of Scripture. These include books such as the Shepherd of Hermas, the Didache, the Gospel of the Hebrews, and the Epistle of Barnabas.

What misconception does this refute? Some people have the impression that the existence of a canon means that the church can never (or should never) use any other books outside the canon. But the early Christians did not share this belief. They saw nothing problematic about using books like the Gospel of the Hebrews and, at the same time, affirming that only four gospels are canonical. Clement of Alexandria is a perfect example of this pattern. He appealed to all sorts of writings, including apocryphal gospels, but was quite clear that he only received Matthew, Mark, Luke, and John as Scripture.

4. Heretical Books. These are the books that are so theologically problematic that they have little (if any) positive value for the church. These are “forgeries” that Eusebius regards as “altogether wicked and impious” (3.25.7). These include books like the Gospel of Thomas, the Gospel of Peter, the Gospel of Matthias, the Acts of Andrew, and the Acts of John.

What misconception does this refute? Some scholars have argued that books like the Gospel of Thomas were just as popular as the canonical gospels and almost made it into the NT canon. But, notice that Eusebius does not agree. He does not put Thomas in the “disputed” category, or even the “rejected” category, but all the way in the heretical category. For Eusebius, such books are not, and never were, contenders for the canon.

In sum, understanding these four categories is an essential step in removing misconceptions about the NT canon that seem to abound today. Knowing these categories can give a person a fairly basic picture of how the canon developed: (1) there was a core canon from a very early time, (2) there was dispute about some of the smaller books that took some time to resolve, (3) Christians continued to find some non-canonical books to be orthodox and helpful, though not Scripture, and (4) some books were so theologically off the mark that they were regarded as altogether heretical.

For more on these four categories, see chapter 8 of my book Canon Revisited (Crossway, 2012).