If only from the fact it is excluded from the canonical (sic) text! The problem comes with why were the biblical texts written at all for they do not describe an historical figure.
The Jesus of the gospels is a famous miracle worker, attracts huge crowds with his teaching, is an acknowledged a scholar and enters Jerusalem in triumph. If Jesus had been that famous there would be far more note made of him in non-Christian sources. Josephus hardly refers to Jesus at all even if you accept the references in his "Jewish War" at face value (which I do not). Philo of Alexandria whose life overlapped the career of Jesus makes no mention this famous rabbi despite writing at length about Pilate's rule in Judea. Valerius Maximus collected memorable sayings and accomplishments during the time of Jesus's life but has nothing from or about that teacher.
What does that leave us with? Just the synoptic gospels; two of which which contradict each other and copy from the third; dubious references from later, non-Christian writers and the non-synoptic Christian writings; both those later included in the bible and those excluded from it.
Didache is one of the excluded, Christian writings. Dating for any early text is difficult; the careers and reputations of numerous academics are made upon assessing the age of texts. Essentially dating it boils down to identifying dated events within the text, assessing the grammar and vocabulary of the text for the period in which it was written and finding when the text is first mentioned by other writers in a dated context. Using these methods I understand that the Didache is dated to between 50 and 120 CE. As an aside it is worth noting that this places the Didache in the same period as the early Pauline letters and the hypothetical, maybe mythical Q document. In addition Didache possibly pre-dates the Gospel of Mark.
Didache and all of the other, Christian writings are connected by two things - they were written and amended long after the time of the putative Christ and we do not hold original copies. On textual accuracy, for example, Marcion complained about the Western Church adding text to early Pauline letters and they in turn accused him of deleting content. The earliest copy we have of Mark is in the
Codex Sinaiticus and that, at the earliest dates to mid-Fourth Century (320-380 CE). This early Mark again shows how texts were altered by the early and later Churches for it contains only 666 verses against the modern count of 678.
Now let me tell you about a miracle that happened during the First World War. In August 1914 British units of the "contemptibly small" British Expeditionary Force were attacked by a very large number of Germans. The force was pressed hard and a massive breakthrough was threatened, but a hugely outnumbered force on a small salient near Mons held out. The situation was dire, if the salient was crushed then nothing would stop the German advance. Then, at the height of the battle something wonderful happened, Germans fell in huge numbers and the remainder turned and ran; the salient held and the British were able to withdraw safely to freshly prepared lines. Near contemporary reports tell of a bright light in the sky, and the appearance of angels conjuring strangely equipped troops from the mists. These troops wore tatters and medieval armour, they carried bows and clothyard arrows. The next day, it is said, Germans recovering their dead did, indeed, find many of their men had died from arrows not bullets.
You may recognise the story of the "Angel of Mons" and the truly miraculous thing about it is that many people believed it really happened. Despite modern printing, record keeping and reporting for much of the 20th Century many people accepted this fable as fact. The real story was that the highly trained, professional troops of the BEF, using one of the best weapons of the century (the Short Magazine Lee Enfield rifle) did hold against a conscript army who vastly outnumbered them. Then, the next month, a fine writer called Arthur Machin wrote a story called "The Bowmen" about this battle which was published in the London "Evening News". For some reason the editor did not identify this story as fiction. To quote Wikipedia:
A month or two afterwards, Machen received requests from the editors of parish magazines to reprint the story, which were granted. A priest, the editor of one of these magazines, subsequently wrote to Machen asking if he would allow the story to be reprinted in pamphlet form, and would he write a short preface giving authorities for the story. Machen replied that they were welcome to reprint but he could not give any authorities for the story since he had none. The priest replied that Machen must be mistaken, that the "facts" of the story must be true, and that Machen had just elaborated on a true account. As Machen later said:
"It seemed that my light fiction had been accepted by the congregation of this particular church as the solidest of facts; and it was then that it began to dawn on me that if I had failed in the art of letters, I had succeeded, unwittingly, in the art of deceit. This happened, I should think, some time in April, and the snowball of rumour that was then set rolling has been rolling ever since, growing bigger and bigger, till it is now swollen to a monstrous size."
—Arthur Machen, Preface to The Bowmen<1>
Around that time variants of the story began to appear, told as authentic histories, including a variant which told how dead German soldiers had been found on the battlefield with arrow wounds.
During my childhood and adolescence I was assured this story was true, it was a "real life" miracle. I know that the event has been cited throughout my life. Can see where this is leading? Despite our literate society, the easy availability of sources and the frequent, well publicised, debunking people still accepted this story of an angel as reality. How much easier then for a Platonic Ideal of a God/Man to be accepted as reality in a non-literate society - and think how quickly this could happen.
I can see how, within 20 years of the supposed death of this Messiah, a believer chose to write down what he had gathered about his "real" God. That other authors hearing of this write their own accounts. All would draw on a common fund of legends, some would use half remembered stories about real people and add them to the mix - or copy the bits they liked from other writers. In all I do not think the Gospels, and the other writings, are gospel true.