The disappearance of ancient books: the accidental disappearance of texts when no copyists of texts was found.
This does not sound altogether incredible. After all, Christian clerics have ordered the burning of books, witches, and heretics in the sixteenth century. Besides, early Christianity had been persecuted, and it is not too strange a thought that the victims decided upon a policy to do to the pagans what they had done to the Christians. Indeed, the angry polemics of the fathers of the Church certainly leave one with the impression that these men were intolerant fundamentalists. However, the wanton destruction of books was rare. It was unnecessary.
It was quite possible to have an opinion that was different from the majority of the Church leaders. There were a couple of theological points that they considered to be important (like the date of Easter and the precise definition of the relation between Jesus and the Creator), but more often, bishops were willing to strike compromises. If people could be saved from Hell by allowing them to continue some pagan cult in a Christian form, the Church would not obstruct it. As a consequence, the cult of the Twins in northwest Spain was converted into the cult of Jesus' brother James, the Greek demigod Perseus became Saint George, and the spruce and fir that decorated Germanic homes during the Yule festival survived as Christmas tree. The great majority of bishops was not interested in the destruction of heretical Gospels or homo-erotic poetry. They were pastors who took care of their flock, and as a consequence, Christianity was multiform and many-colored.
And even if the Church would have wanted to enforce an orthodoxy, it would have been impossible. An interesting parallel is the Roman government, which was incapable of unifying Roman law. It is significant that several emperors are credited with a Lex citandi, a law that established which juridical texts were acceptable authorities. The fact that these laws had to be repeated, proves that not everyone knew, understood, or accepted them. If the powerful emperor and his legions were unable to unify legal practice, the Church was certainly incapable of unifying beliefs.
As far as we know, possessing unChristian texts was not considered to be a sin. The fact that the fathers of the Church were able to quote them, is decisive evidence. A treatise like Celsus' True Account has been quoted so extensively, that modern scholars have been able to reconstruct its contents.
So, if early Christianity was multiform, and if the Church was incapable of enforcing the few beliefs it would have liked to prescribe, why did so many ancient texts disappear? Where have the Gospel of the Egyptians and the poems of Sappho gone? Why can't we read those books by Suetonius with tantalizing titles like Lives of famous prostitutes, Dictionary of invectives, and - last but not least - Physical defects of men? The answer may sound like a sophism, but it isn't: these texts are lost because they were not saved. The main difference between now and then, between us and them, is that today, a text survives unless it is destroyed, whereas in Antiquity, a text disappeared unless it was saved.
Ancient texts were typically written on papyrus, which is vulnerable. As a rule of the thumb, we can assume that a scroll had to be copied every century. If parchment was used, replacement could take place less frequently. The parchment copy of Julius Caesar's Gallic War shown on the picture is more than thousand years old. However, preparing a skin and making parchment was extremely expensive. Most texts were, therefore, written on papyrus and subject to decay and disappearance. If there were many copies of the same text, the chances of survival were greater, but professional writers were expensive and texts usually circulated in small numbers. A surprisingly great number of ancient texts has survived in only one copy, which shows how vulnerable the process of transmission was.
The best way to conceptualize the process is, therefore, that ancient texts always disappeared, unless a rich lord or lady decided to hire a scribe and copy a scroll. Inevitably, selections were made. There was no need to copy the Histories of Valerius Antias once Livy had published the History of Rome from its Foundation; there was no need to copy the speeches of Greek orators of the third and second centuries BCE because the sophists of the second century CE were so much more eloquent; and there was no need to copy archaic poetry like Sappho's because it was written in a poorly understood, archaic language. The publication of new texts was the greatest danger for the survival of older texts.
The same applies to religious texts. The religious authorities did not need to make an Index of prohibited books; the books they did not like were bound to disappear anyhow. Once the rabbis of Yavneh had decided which works were divinely inspired, these works were copied and the remainder (e.g., the Enoch literature) was not. The temple establishment of ancient Greece may not have liked the ideas of the charismatic teacher Apollonius of Tyana, but destroying his book On sacrifice was unnecessary.
The question is not why certain texts have disappeared, but why others have survived. In the second century, a man named Marcion of Sinope proposed to reduce the number of Christian texts. The Old Testament, he argued, was no longer useful to the believer, and there was no need to waste money on copying it. The Gospels often repeated each other, so it was better to create one single, authorized version.
Several bishops, including Irenaeus of Lyon, responded. They thought that the new faith needed more than one account of the life of Jesus, and therefore several Gospels, even if they contained repetitions. Christianity also needed the Jewish Bible. The agreement on this plurality was decisive for the survival of religious treatises. For example, the Christian scholar Origen prepared an important scientific edition of the Hebrew text (the Hexapla), and for the first time, books were published that contained more than one Gospel.
The agreement that at least four Gospels, the Acts of the Apostles, several epistles, the Book of Revelation, plus the entire Jewish Bible (and even a bit more than the Jews accepted) was needed for the new faith, was not a decree against other texts. However, the result was comparable.
The people who accepted Marcion's suggestion started to develop the ideas that are now called Gnostic, and the Gnostics started to write treatises of their own (like the Gospel of Thomas, the Secret Book of John, and the recently discovered Gospel of Judas). There must have been many of these texts, but they are lost.
Like all ancient texts, they needed scribes to survive, but the Gnosis never recruited enough people. Its ideas were too austere. Unlike other branches of Christianity, the Gnosis made a sharp distinction between good and evil, between the good God of Christ and the evil creator worshiped by the Jews, between mind and matter. The implied hostility towards sexuality made the Gnosis unattractive and by the end of the third century, Gnosticism was a small minority within the wide variation of Christian beliefs.
In the end, it was a man named Hosius of Cordoba who convinced the emperor Constantine, who already sympathized with monotheism, that he should accept Christianity. Like Irenaeus and Origen, Hosius believed that the Jewish Bible was of vital importance and because the emperor agreed, senators started to convert to this type of Christianity too. Soon, the believers started to organize themselves, and many others accepted the Christian beliefs as they had been interpreted by Hosius.
Most Gnostic texts did not survive. Not because the leaders of the now dominant type of Christianity launched a war on Gnosticism, but because ancient texts needed copyists, and the Gnosis had been unable to recruit sufficient people for the survival of its ideas.