Indeed a post-70 CE date is confirmed by Clement's Letter to Theodore. Tradition generally assigns both Peter's presence in Rome and Mark's subsequent voyage to Alexandria to the same period. While very little (or 'absolutely no') scholarship has been done on the Marcionite dating of its apostle, it should be noted that there are places in his letters which could only have been written after 70 CE. The most notable example is that which appears in what is now called the First Letter to the Thessalonians. We read:
For you, brothers and sisters, became imitators of God’s churches in Judea ... (who) suffered from the Jews who killed the Lord Jesus and the prophets and also drove us out. They (the Jews) displease God and are hostile to everyone in their effort to keep us from speaking to the Gentiles so that they may be saved. In this way they always heap up their sins to the limit. The wrath of God has come upon them at last
Of course scholars explain this reference to the destruction of the temple as a "deutero-Pauline interpolation." In other words, someone came along after the time Acts tells us Paul was active (Acts never makes reference to the existence of the epistles) and inexplicably 'added' these words which belong to another time.
The difficulty with this explanation of course that there are other intimations that the canon was developed in a post-70 CE era. With respect to the 'secret gospel' the Homilies attributed to a first century figure in the Roman church read - "and thus, as the true Prophet (Moses) has told us, a false prophet must first come from some deceiver; and then, in like manner, after the removal of the holy place, the true Gospel must be secretly sent abroad for the rectification of the heresies that shall be." By implication then the 'secret gospel' was a reaction against a spurious text associated with a heretic named Simon. In a similar manner the second century Christian historian Hegesippus speaks of sectarian traditions 'as living underground, burrowing' in secret until the reign of Trajan. It was because Christianity was essentially a subterranean culture that heretics were frequently identified as 'foxes.' Only in the subsequent reigns of Hadrian and Antoninus Pius that individual heretics begin to come above aground as it were and allow themselves to be recognized.
While Bart Ehrman does manage to ask - "why is it that Clement himself never mentions the letter, or the Secret Gospel ... in all his other writings?" - his intimacy with early Patristic sources is apparently not up to the task of answering his own question. That Clement, the doesn't reveal the secret he is sworn not to divulge is hardly as surprising as Ehrman's inability to reference all the allusions to the existence of a 'secret gospel' in other early sources. Others certainly proposed the development of such a text from the evidence of Patristic sources alone. As Morton Smith noted in his 1972 study - "it is interesting, that (the English translator of Irenaeus William) Harvey, in his note on this passage, was led to postulate the existence in Egypt of a secret Gospel according to Mark — a conjecture which the present text confirms."
Yet can we know begin to explain the 'secret' or 'mystical' nature of the composition through referencing the cultural landscape of the post-70 CE period? The rabbinic tradition certainly speaks of Judaism going 'underground' in the very same period. Nevertheless perhaps the most convincing piece of evidence in this respect is again the Christian use of the codex. As we have already noted Christianity was, not only "addicted" to the codex as F G Kenyon once quipped it was properly defined by Benjamin Braude as the very "codex religion." While we have previously referenced the portability of the codex it should also be noted that traditional Judaism inherently associated the format with secrecy and heresy.
A very early rabbinic tradition tells us that that when one very famous heretic "used to rise from the house of learning, many heretical books used to fall from his lap" (B. Hag. 15b) The famous story is generally interpreted as follows:
Elisha ben Abuya, who lived in the time of the Emperor Hadrian, and, turning apostate from the Jewish Religion, became a fanatic follower of Gnosticism. Elisha, from his earliest youth, showed a decided supersubtle Greek philosophy, fashionable in his days, and whilst standing in the Beth Hamedrash (the House of Learning), seemingly absorbed in the study of the Law, these profane and heretical books were hidden in the folds of his mantle
As we have no direct evidence from Christian sources the practice of Jewish heretics related to Christianity must be admitted into our study. Indeed the Jewish perspective is especially interesting given that Judaism continued even after the destruction of the temple to be a religion of rolls. Elisha's attachment to codices was seen as an inherently foreign practice connected with secrecy. After all, one could not hide a traditional scroll.
