It is, I think, just this un-assorted residue that gives us the clue to the early history of the text of the New Testament. It is not always realized how unique were the conditions under which these books circulated in the early centuries. The ordinary works of classical literature were freely copied by professional scribes, and it is probable that the tradition of their text has come down to us mainly through the great libraries and the book-producing firms of capital cities. Even the books of the Greek Old Testament must for the most part have descended through untrammeled channels, except so far as they may have become involved in the fortunes of Christian literature. But the Christian books, before the recognition of Christianity by Constantine, were produced and circulated without the assistance of great libraries or a regular trade. Scholars need to apply the increased knowledge which we now possess of this period to the problems of the New Testament text, and to use both imagination and common sense in interpreting them.
The New Testament was not produced as a single work issued by an authoritative Church for the instruction of its members. The four Gospels were composed in different times and places over perhaps a third of a century, and for a time circulated separately among a number of other narratives of our Lord's life (of which the newly discovered fragment of an unknown Gospel may have been one). The Epistles were letters, or treatises in the form of letters, addressed to different congregations and only gradually made known to other Churches. The book of Revelation was an isolated production, which for a long time was not universally accepted. There was no central body to say what books were to be regarded as authoritative, or to supply certified copies of them. The apostles were scattered, and even the leaders of the Church in Jerusalem had neither the power nor the means to impose uniformity.
In these circumstances, we must imagine the literature of Christianity as spreading gradually, irregularly, and in a manner which made variations inevitable. In the earliest days, while the generation that had known our Lord on earth was alive, and while His second coming was expected in the immediate future, there would have been little demand for written records. But as the promise of His coming was delayed, and as the faith spread beyond the range of those who had known Him, the narratives which we now know came into being, together with many which have long ago disappeared. But not every congregation would have possessed a complete set of the books of their faith. One church might possess only one Gospel, another two or three or the complete four. A village or provincial town where there was a Christian congregation might hear that its neighbor had a copy of a book unknown to them, and might send and get a copy of it - made, very likely, by a copyist of more zeal than skill. Exact verbal accuracy of transcription was, after all, of little account. The Gospels were not thought of as works of literature. People were not concerned with the literary reputation of Matthew or Mark, but with the substance of their records of our Lord's life. They did not have to respect their actual words, as they would if they were transcribing the works of Thucydides or Plato. Rather a scribe might have thought he was doing good service if he smoothed away difficulties of phrase, if he made the narrative of one Evangelist conform with that of another, if he inserted proper names or pronouns for the sake of greater clearness, if he used a conventional form of words instead of an unusual one, even if he inserted a new incident into the narrative. Edification was the object, not literary exactitude.
In these circumstances, is it surprising if in the first two centuries a large number of minor variations, and some of greater magnitude, found their way into the copies of the Scripture which circulated in the towns and villages of Palestine, Syria, Egypt, Asia Minor, Italy, Africa, and even farther a-field? Rather we have to be thankful that greater and more serious corruption did not creep in. It is indeed a striking proof of the essential soundness of the tradition that with all these thousands of copies, tracing their ancestry back to so many different parts of the earth and to conditions of such diverse kinds, the variations of text are so entirely questions of detail, not of essential substance. For the main substance we may be content even with the latest copies which have handed down to us the ecclesiastical text of the Middle Ages. But if we wish to read the sacred books of our religion in a form as like as can be to that in which they were originally composed, we must endeavor to realize the conditions under which they were produced, and which we have been trying to describe.
from Chapter 10, The Story of the Bible