And why do they believe that? Can I be so honest as to say that this is what scholars often do - make mountains out of molehills. Well there I said it. It's 'fun' and 'fascinating' to make believe that we can for instance reconstruct the Jewish War based exclusively on a single source - Josephus. It isn't a 'perspective' on the events of 66 - 72 CE. No, no, no. 'The Jewish War' is now entirely defined by what Josephus preserves for us in his tomes. 'The Jewish War' is the Jewish War.
The same thing happened with respect to Marcion. There is a phenomenon. It is called 'Marcion.' Countless Church Fathers make reference to this phenomenon. So in order to understand who or what 'Marcion' is all we need to do is gather together what 'all' the sources say - giving greater weight to the earliest witnesses. For instance, the similarities between what Tertullian says about 'the gospel' in the context of refuting Marcion and what Epiphanius says about the Marcionite gospel while claiming he is citing directly from the Marcionite gospel, seals the deal for them. Tertullian and Epiphanius can be read together to help us 'know' what the Marcionite Bible 'looked like.'
But can anything be more stupid than this proposition? Epiphanius claims that he has before him the Marcionite 'Gospel' and the Marcionite 'Apostle' sitting in front of him and that he has enumerated all the variants in their Bible. He notices 118 'differences.' And yet, if we take every 'textual reference' in Tertullian's Adversus Marcionem to be 'textual references' to the Marcionite canon - Epiphanius's 'complete list' and Tertullian's list of citations don't exactly line up with one another. There are underlying references that 'agree' but more often than not Tertullian makes reference to 'things said in the Scriptures' - citations of Scriptures presumed by scholars to be verbatim citations from the Marcionite canon - which don't line up with the 'complete list' in the Panarion.
My explanation for this situation is that scholars have it all wrong. Neither man had the Marcionite scriptures in front of them when writing their tome. Tertullian, for instance, in Books Four and Five of Adversus Marcionem is drawing on an older work, likely written by someone in the circle of Justin Martyr, which had little or nothing to do with Marcion at all. The same situation occurs in Book Three of Adversus Marcionem. Material originally directed 'Against the Jews' has been refashioned into a treatise 'Against Marcion.' Why, how, when and the like don't matter here. It is what happened with Book Three so the likelihood that it also happened in Books Four and Five already start on firm ground.
What I say is that the author of the material in Books Four and Five was citing from his own canon of scriptures originally for reasons that had little or nothing to do with Marcion. In Book Four for instance he was just explaining how to interpret the gospel properly and along the way Marcion is referenced. In this original source Marcion is often accused of cutting things from his gospel which never appear in Luke at all. In other words, the original line of attack had nothing to do with Marcion corrupting a 'gospel of Luke' at all. The author didn't know separated gospels of Matthew, Mark, Luke and John and instead as a member of the community of Justin and Tatian used a so-called 'gospel harmony' - hence the references to 'things Marcion deleted from his gospel' that only now appear in Matthew.
By the time that his ur-text reached Tertullian (i.e. by way of Irenaeus) it had been transformed into an attack against Marcion where the 'gospel of Marcion' was defined as being a mutilated version of Luke. Irenaeus added this to the text. But even here and in our final edition of this work (note that the introduction of Adversus Marcionem acknowledges the text was written and rewritten three times passing through different hands) there is absolutely no evidence anwhere which support the claims of modern scholarship that the author of Adversus Marcionem had before him the 'actual' Bible of Marcion.
Of course I can completely understand why scholars like to read the text that way. When we watch a movie like Star Wars very few of us watch the movie from the perspective of George Lucas making the film. 'I wonder why he did that?' 'I wonder what that looked like sketched out on a storyboard.' Most of us prefer what we might call a 'superficial perspective' where we enjoy the story without thinking of it as a story. The same thing applies to the study of Patristic literature. Adversus Marcionem is a more enjoyable read - its an easier read - if you just assume that Tertullian had Marcion's Bible in front of him.
But 'what's easy' isn't always the same thing as 'what's true.' There are so many layers to Adversus Marcionem. For instance there is the recurring 'Marcion cut something from the gospel' which isn't from Luke but Matthew. Another layer is certainly the constant resurfacing of Greek terminology within a Latin text. There are entire chapters that seem directed against 'the Jews' and only superficially adapted to fit the 'Against Marcion' theme. I could do on and on but in the end I have to conclude we can't use Tertullian to reconstruct Marcion's Bible. The only reason we pretend that Adversus Marcionem is doing anything other than citing from an orthodox Bible (an orthodox edition of Luke and the Pauline letters which greatly resembled Codex Bezae or the Old Latin) is that we are influenced Epiphanius, a Church Father who lived a century after Tertullian.
Epiphanius claims repeated that he has before him the Marcionite Bible and his testimony at times agrees with Tertullian and other writers. But the parallels with Tertullian have been misunderstood. Epiphanius is lying about having the Marcionite Bible in front of him and instead has compiled a list of anomalies from works like Adversus Marcionem (albeit likely in the form originally set down by Irenaeus) and misrepresented why he knows so much about Marcion. It is a situation very similar to the one reported in Ehrman's Forgery and Counter-Forgery.
Ehmran concludes that Epiphanius is lying and deceiving his audience with regards to his section on the so-called Borborites - the 'filthy.' He says he has their scriptures in front of him in that chapter just as he says he has the Marcionite scriptures in front of him in chapter 40. Lies, lies, lies. As noted previously his near contemporaries referred to Epiphanius as being somewhere between a 'fool and a demon.' The material that makes up his Panarion often suffers from his periodic exaggerating the quality of his information and on the other hand - and equally perplexing - his frequent plagiarism of ancient sources without acknowledging that he is in fact copying out sources near verbatim.
So it is when it is that we get around to explaining why Epiphanius didn't send his Προοίμιον τῆς περὶ τῶν Μαρκίωνος βιβλίων ὑποθέσεώς τε καὶ ἐλέγχου - his 'outline' (ὑποθέσεώς) of the Marcionite Bible immediately to the two Syrian monks who originally requested it we have to assume he was aware that his exaggerated claims might be exposed. He was not citing material directly from the Marcionite Bible. This was, rather, a cobbling together of textual anomalies that came up as a result of two centuries of anti-Marcionite literature. In other words, it was all based on secondary and tertiary information about the sect. In short, it was a much less valuable source of information about the Marcionites than what he claims.
For instance in the outline (ὑποθέσεώς) itself he writes that Marcion "will be refuted from the very works which he acknowledges without dispute from the very remnants of the Gospel and Epistles which he still has." This has a definite Irenaean ring to it. He goes on to say that:
[s]ome years ago, to find what falsehood this Marcion had invented and what his silly teaching was, I took up his very books which he had mutilated, his so-called Gospel and Apostolic Canon. From these two books I made a series of extracts and selections of the material which would serve to refute him, and I wrote a sort of outline for a treatise, arranging the points in order, and numbering each saying one, two, three (and so on). And in this way I went through all of the passages in which it is apparent that, foolishly, he still retains against himself these leftover sayings of the Saviour and the apostle. For some of them had been falsely entered by himself, in an altered form and unlike the authentic copy of the Gospel and the meaning of the apostolic canon. But others were exactly like both the Gospel and Apostle, unchanged by Marcion but capable of completely demolishing him. By these it is shown that the Old Testament is in agreement with the New, and the New with the Old.There is thus an explicit claim that in this outline he has "went through all of the passages" in the Marcionite gospel which is supposedly before him. But if this is true then the outline for the most part does not agree with Tertullian; Tertullian can't be citing from the Marcionite Bible but his own throughout Adversus Marcionem.
The problem comes up over and over again in the introduction and conclusion of the outline. We read again that Epiphanius acknowledges that:
I found that this compilation had been tampered with throughout, and had supplemental material added in certain passages—not for any use, but for inferior, harmful strange sayings against the sound faith, fictitious creatures of Marcion’s cracked brain. I have made this laborious, searching compilation from the scripture he has chosen, Paul and the Gospel according to Luke, so that all who are attempting to contradict his imposture may understand that the altered sayings have been fraudulently inserted, and that any not in their proper places have been stolen from them by his audacity. For the oaf thought that only these run counter to his false notion. But there is a third work of my scholarship: the compilation of whatever material he and we have in common, and whose meaning is the Saviour's incarnation and his testimony to the agreement of the New Testament with the Old—and the acknowledgment in the Gospel, by the Son of God, that God is the maker of heaven and earth and the same God who spoke in the Law and the prophets, and that this God is his own Father. And here is the brief arrangement of that work of mine, transcribed word for word by myself from copies of Marcion in the form of scholia with exegetical comments, to serve as an outline. But so that the difficult things in it will not be obscure to some and fail to be understood, I shall in turn explain of the several entries in order—I mean the first entry, the second, the third (and so on)—the reason why each saying was selected and transferred here. I begin as follows.We have already noted that Epiphanius is lying about having Marcion's Bible in front of him. Tertullian or his source was one of Epiphanius's sources which explains why Epiphanius - drawing from Adversus Marcionem which draws from the author's own orthodox but ultimately unusual canon of scriptures 'agrees' with Tertullian in many places.
Again in the conclusion we see the false claims being promulgated by Epiphanius. He summarizes by saying:
This is my treatise, prefaced in the foregoing selections from the scripture which is still preserved in Marcion's own canon. Anyone who examines its collection (of texts) must be struck with awe at the dispensations of the bountiful God. If every matter is attested and established by three witnesses, how has God granted me, by a dispensation, to put together here, as I said, a sheer total of 78 testimonies from the Gospel, and 40 from the Apostle? And these are preserved in Marcion to this day and not disputed, so that there are 118 altogether, and all contradicting Marcion's own opinion—as though in the person of the Lord's name through eighteen, and in the name of the blessing on its right through the hundred. And in addition to these he is refuted in another, further testimony, the one outside of the Gospel and The Apostle. For the utter wretch Marcion did not see fit to quote this testimony from Ephesians but from Laodiceans, which is not in the Apostle. Since, among his many failures, the oaf foolishly does not read these testimonies, he pathetically does not see the refutation that awaits him, although it is on record every day. And no one need be surprised at this. Since he professed to have some of the Gospel and Apostle, how could he help preserving at least a few words of the scripture? Since sacred scripture's whole body, as it were, is alive, what dead limb could he find agreeing with his opinion, in order to drag in a falsehood against the truth? Instead he amputated many of the limbs, as we might say, and mutilated and falsified them, but retained some few. But the very limbs he retained are still alive and cannot be killed, but have the life-giving property of their meaning, even if, in his canon, they have been cut off in innumerable small chunks.
Clearly Epiphanius has misunderstood the statements in Tertullian regarding "another epistle, which we hold to have been written to the Ephesians, but the heretics to the Laodiceans" and assumed - wrongly - that these were two separate texts. The clearest proof again that Epiphanius did not have the Bible of Marcion in front of him. Ehrman's point about Epiphanius's reporting on the Borborites is doubly true with Marcion - the Church Father is lying.