Noncanonical writings are early Christian documents that are not found in the New Testament. The list of writings in the New Testament are known as a canon, a term that comes from a word meaning “measuring stick” or “rod.” There are many different canons in different religious and even literary traditions; whatever list of writings a particular community considers authoritative constitutes a canon. The writings included in a canon are called “canonical.” Scholars of early Christianity therefore often divide up writings into the categories “canonical” and “noncanonical.”
However, things are actually a little more complicated than this. First of all, the canon of the New Testament formed only very late (around the fourth century C.E.). Even then, it differed slightly from our New Testament canon today. What this means is that in the second and third centuries, when many Christian documents were being written and circulated, Christians didn’t yet have a sense of which writings were canonical and which noncanonical, because there was, as yet, no New Testament canon. It is therefore not accurate to call key texts like the Gospels of Matthew, Mark, Luke, and John canonical when referring to the second century. To give another example, Paul’s letters were circulating in the second and third centuries—probably as a packet—but these, too, were not yet canonical at the time.
Since this is the case, you might think that the category of “noncanonical” could just mean any Christian text written before the canon was developed, but that’s not the way we use the word. This is because the category itself is quite old, and it derives from a particular bias in biblical scholarship of the nineteenth century, where only Christian documents that made it into the New Testament were considered valuable, and others were considered spurious, or worse, blasphemous and foolish! Scholars nowadays, by contrast, recognize that even Christian documents that are not part of the New Testament have a great deal to tell us about early Christianity, particularly in terms of how people understood Jesus and what it meant to be Christian.
Noncanonical writings fall into different kinds, or genres. We have letters that early Christians exchanged, for example. We have apocalypses, gospels, and sermons. We have many Acts of the Apostles. We have prayers, poetry, and revelatory texts in which Jesus discloses special knowledge to his disciples. All of these writings are considered noncanonical in the way we use the term today. They are also amazing and valuable texts for teaching us about what early Christians believed and how they behaved; our understanding of Christianity’s formation would be hugely impoverished without them. Some of the more famous noncanonical writings include texts like the Gospel of Mary Magdalene, the Gospel of Judas, the Protevangelium of James, the letters of Ignatius and Clement, and the apocryphal acts of the apostles. There are hundreds more, many of which were hugely popular in Christian antiquity and considered important sacred texts. We know this because some exist in multiple translations, or in multiple ancient copies. Some of them, like the letters of Ignatius and Clement, were even considered canonical texts in certain Christian denominations.
So how is an “apocryphal” writing different from a “noncanonical” writing? Some people use the words interchangeably. Technically, though, they’re different things. Apocrypha comes from the Greek word meaning “hidden,” and yet not all apocryphal texts were necessarily hidden away in the ancient world. Apocryphal also has a colloquial meaning of “untrue” (as in “her story sounded apocryphal to me”), but that’s rather an unfair way to think of these texts: they were no more untrue than they were hidden. Nevertheless, both types of writings—noncanonical and apocryphal—share one thing: they are not in the main New Testament canon that we have today.
Another problem, however, is that even modern Christianity does not adhere to a single canon. If you look carefully, you might notice that a Catholic Bible is slightly different from a Protestant Bible. In fact, Catholic Bibles often say on the front that they contain the Apocrypha. Here, Apocrypha cannot mean “noncanonical,” since the writings are in fact part of the Catholic canon. They refer to texts that early Christian theologians considered useful in a church context, but that were not considered divinely inspired. Modern Christianity is diverse; so many denominations have ancient origins and their own distinctive canons. The Syriac Christian Bible (known as the Peshitta) used by Syrian Orthodox Christians originally lacked writings in the Western New Testament canon, including 2 and 3 John, Jude, and 2 Peter. The equally ancient Ethiopian Orthodox Church has a broad canon—in the sense that as many as 70 different writings are considered authoritative.
Even in the ancient world, texts could move between canonical and noncanonical status. For example, there are a number of writings—including the Epistle of Barnabas, the Shepherd of Hermas, and Paul’s Epistle to the Laodiceans—that were “canonical” at some point in antiquity but are noncanonical today. The book of Revelation provides a counterexample: it was rejected by many more orthodox-leaning Christians and is absent from early canon lists (including the Peshitta and the New Testament of the Armenian Orthodox Church) but is now a canonical writing in virtually all modern Christian denominations.
There are many published collections of noncanonical Christian writings out there, and most are also freely available on the Internet. They’re worth taking a look at: you may find some interesting and familiar-sounding things. Sometimes even if a text didn’t make it into the canon, it could still be influential. If you read a noncanonical text, you might be surprised to find the origin of a common belief in Christianity that has no basis in canonical writings. For example, the ideas that there were three magi at Jesus’ birth and that their names were Caspar, Balthazar, and Melchior come from noncanonical sources, as does the claim that there were various animals, such as oxen, present around Jesus’ manger. This attests to the popularity of noncanonical texts and the degree to which they shaped Christian understandings of the world, perhaps even as much as the writings of the New Testament.