In addition to the twenty-seven books of the New Testament, early Christian authors produced a number of other important works. It is important to keep in mind that the formal canon of the New Testament was not finalized until around 198 C.E. Previous generations of Christians may well have been in general agreement about what constituted the core of their scripture, but until the late second century, some factions continued to claim the status of divine inspiration for a number of texts eventually judged to be apocryphal and thus not part of the Canon.

Most prominent among those apocryphal writings are a sizeable group calling themselves Gospels. Some (such as the Gospels of Thomas and Philip) were an attempt to support the views of tendentious or heretical factions, while others (such as Gospels of Nicodemus and of the Childhood of Jesus) purport to fill in the gaps of Canonical texts with legend and lore. Apocryphal works called “Acts” and identified with one or another of the Apostles generally, but not necessarily, reflect heretical views. Writings by a group of post-biblical authors known as the Apostolic Fathers, mostly of the late first or early to mid-second century, provide important information on the concerns and theological themes of bishops and their communities throughout the Mediterranean basin. A third significant corpus of writings dating from about 120 to 220 C.E. are those of authors known collectively as the Apologists. Major figures like Justin Martyr (c. 100-165), who founded a Christian school in Rome, and Tertullian (c. 160-220) of Carthage (in present-day Tunisia) and later Rome, wrote in defense of Christian views when outsiders mounted theoretical or political attacks against them.