...is a really cool word. It has nothing to do with Sudafed or pigs. Also, it's not related to the game Sudoku (or its cousin game Real Ku).
Nope. It's a three dollar word for "writings that claim to be written by some Famous Person but are really not."
One of the marks of a lot of early fake Christian (and Jewish) literature as that they are pseudepigrapha: they almost always claim to be by some important Heavy Hitter in the early Christian community: Mary Magdalene, Philip, James, Peter, Thomas.
The reasons for this are not far to seek, though we moderns (who habitually believe that anybody making religious claims is a fraud and a liar) tend to batten on one reason: namely, when you are trying to get your lie across, it helps to attribute your lie to Trusted Authority Figure.
That is, to be sure, a real motivator. And so the gnostics constantly invent gospels to communicate their version of what Talking Head Jesus says on behalf of the particular gnostic sect's teaching--and then attribute it to Thomas, Philip, Judas, or Whoever. Even more amazing is that moderns--subjecting the canonical gospels to a searching and ridiculously skeptical scrutiny that no other ancient document comes close to receiving--then turn to the obvious fabrications of the gnostics with the credulity of a five year old and declare them real sources of information about the Historical Jesus that, as the saying goes "challenge the claims of the Official Church".
That's a special kind of dumb, right there. Like the dumb of the person who seriously imagines that some guy with a website and a couple of blurry photos "challenge the claims of NASA that we landed on the Moon." But the fascinating part for me is what is missed in appeals to the supposed "apostolic source" for a gospel like the fake Gospel of Thomas.
It is this: precisely what is interesting about the canonical gospels of Mark and Luke in particular is that their authors are, well, nobodies in the early Church. Search the rest of the New Testament and you find only passing mention of them. Mark's house seems to have been a meeting place for the early Church. He turns up in Acts, first accompanying, then bailing on, and finally becoming a bone of contention between Paul and Barnabas. Finally, his name is dropped in one of the Petrine epistles. Likewise, Luke gets a brief mention by Paul, along with the zillion other names mentioned in his various greetings to sundry early Christians about which almost nothing is known.
So: how is it that these completely unimportant people wind up getting their names attached to their gospels? Why those guys and not, say, Andrew, or James the Greater, if the gospels are just literary fictions cooked up by the early Church and put in the mouths of apostles to lend the whole thing an air of eyewitness credibility? If these gospels are phony, it's like forging a history of the Reagan Administration and then attributing it to the White House gardener and janitor. Why these guys?
Obvious reason: because Mark and Luke are, in fact, the authors of their gospels and the Church's tradition is that of a living community that remembers who wrote them and preserves that fact in their Tradition. In short, we are getting from them pretty much what they tell us: a written account of the life of Jesus Christ as they have it from the apostles whom they know personally, as well as from the liturgical sources they have received and (in Mark's case) from what he himself saw and experienced with Jesus (a fact he obliquely alludes to when he, alone of all the evangelists mentions the inciden of his running off naked in the Garden of Gethsemane).
Not that linguistic flexibility has *no* place in ancient writers. An oral culture that undertakes to put a Tradition in writing is not super fussy about getting the ipsissima verbi (exact wording) down and will often content itself with getting the gist, or with summing up somebody's life and teaching in a saying that, while they didn't technically say it, sure could be something they would have said had they thought of it. Examples of this abound in the lives of the saints. So, for instance, St. Francis never said, "Preach the gospel at all times. Use words when necessary." But it's a typically Franciscan sentiment. Likewise, St. Teresa of Avila never said "Christ has no hands but yours" and Chesterton never said, "When people stop believing in God, they don't believe in nothing. They believe in anything." Yet these also sum up much of what these teachers really do have to say.
That said, it is a huge mistake to assume that gospels are *that* loose in reporting Jesus words and deeds. Exactly the reason the gospels are written is to prevent, not facilitate, the creation of legends that invent and add to the Tradition the apostles are, with great care, handing on. Indeed, what is striking is how similar the stories recounted are, and how obviously close up to he fact and events they are. As Richard Bauckham makes clear, what we are--painfully obviously--looking at is eyewitness testimony, not myth or legend, recounted according to the canons of historiography as understood by ancient Greco-Romans.
Are the accounts identical? Of course not. But neither are they all that different. In recounting events in the life of a *preacher* there is plenty of source material that will differ depending on what the speaker said on various occasions. So, for instance, it is quite possible that Jesus said both, "Blessed are the poor" and "Blessed are the poor in spirit" depending on who he was speaking to. Likewise various other sayings and incidents are reported with various wordings or else are arranged differently by different gospels in order to make different points to different audiences. Matthew has Jesus going up a mountain like a second Moses promulgating a New Law in the Sermon on the Mount (because he is talking to Jews and demonstrating that he is the *Jewish* Messiah). Luke collects many of the same sayings but has Jesus speak on a plain (because he is showing Jesus as the brother and savior of the whole human race). Both are giving us a true account of what Jesus said, but not in the way a modern historian would.
Other times, the gistiness of the account is dealing, not with multiple occasions on which Jesus said more or less the same thing, but with unique and unrepeatable events, most notably the Passion. Fundamentalists obsess over stuff that the original writers take a much looser approach to. Did the sign on the Cross read "This is Jesus the King of the Jews" (Matthew), "The King of the Jews" (Mark), "This is the King of the Jews" (Luke) or "Jesus of Nazareth, the King of the Jews" (John). Obsessors over the need for nitnoid accuracy come up with attempts to "harmonize" the accounts (usually involving the claim that since the sign was in Hebrew, Latin and Greek it must have said all these things in different languages--all while overlooking the fact that there are four, not three, wordings of the sign in the four gospels). Sensible people don't worry about things and get the point of the gospel writers: that Jesus was crucified on the charge of claiming to be the King of the Jews.
The same habit of getting the gist is seen in the Eucharistic narratives, where (on the only occasion he said this) Jesus says "Take, eat; this is my body" (Matthew), "Take; this is my body" (Mark), and "This is my body which is given for you. Do this in remembrance of me" (Luke). The only thing dumber than the fundamentalist insistence on looking for the exact wording of this real historical event is the fundamentalist atheist notion that since the wording is not identical in each gospel, the whole thing therefore never happened and Jesus never existed. This is as stupid as insisting JFK never existed since witnesses have slightly different recollections of the exact words and events in Dealey Plaza on November 22, 1963.
A couple of final points:
First, in addition to the curious fact that the canonical gospels of Mark and Luke are attributed to nobodies in the early Church, they are also distinguishable from gnostic gospels by the same thing that distinguishes all the canonical gospels: namely, that they are, in the memorable words of one German theologian "Passion narratives with long introductions". That is the mark of a canonical gospel: about a quarter of the ink of each of the gospels is spent on a 72 hour period in the life of Jesus. All the stories and sayings in the first part of the gospels are simply introductory materials for the Main Story, which is the passion, death, and resurrection of Jesus. If you don't get that, you don't have the slightest idea what the gospel is really about. For the same reason, if you take some random saying of Jesus as being what the gospel is "really" about and regard the passion narrative as something tacked on to the chatter of, say, a mere moralist or apocalyptic theorist, you are likewise clueless. The core story *is* the passion narrative. The morals, miracles, and apocalyptic teaching are all commentary offered in light of that. The reason the evangelist gives a rip about Jesus' teaching in the Sermon on the Mount or his apocalyptic homilies is because it is the preaching of the Son of God who rose from the dead. The Resurrection throws light backward on the career of Jesus even more than the career of Jesus illuminates the meaning of the Resurrection.
Second, what is remarkable is that the canonical gospels have, so to speak, nothing to prove as far as authorship goes. Their authors don't even bother to sign their names while the pseudepigrapha constantly plaster the alleged names of their authors and beat the reader over the head with their fake authority. Nor is there much controversy in the early Church about the canonical gospels. They naturally take their place in the liturgy while the pseudepigrapha are never taken seriously despite their loud claims to apostolic authorship. That's not because of a conspiracy. It's because early Christians trusted the testimony of their fathers and mothers in the faith just as you know that watch and diary your dad gave you belonged to your grandfather.
By the late second century, we already have St. Justin Martyr (a layman, by the way) referring to the gospels as the "memoirs of the apostles". And it is obvious that the liturgy he describes (which includes not just the reading of the gospels but the recitation of good chunks of the eucharistic narrative) is already ancient. This is a Church of memory, not myth.