How many times have I heard from some 'expert' that that the Marcionites used a gospel written by Paul? This even though Tertullian tells us explicitly that this is not the case. The breakdown comes owing to the essential incompatibility between our Christian paradigm and theirs. It's that simple. We identified the author of the Apostolikon (the so-called 'writings of Paul') as being named 'Paul' and Marcionites simply did not.
Yes to be certain the Marcionites said that the author of the Apostolikon wrote the Marcionite gospel. But the Marcionites said that the author of the gospel was named ... Mark or Marcion (which is just a diminutive of Mark). You can see this time and again in the Patristic writings. Tertullian identifies the Marcionite gospel as 'the gospel of Marcion,' Eznik says that Marcionites say that Marcion had the 'unspeakable' vision in 2 Corinthians 13.4 and then there is the report in al-Nadin's Fihrist in the years 987/88.
The Fihrist is admittedly a late report from unacknowledged sources, however these objections are dismissed given the fact that (a) the source tells us that Marcionites were still living in Turfan alongside Manichaeans in the region and (b) we have discovered Manichaean documents in Turfan. It is unfortunate that I can't find an English tranlsation of the original material so I will make a rough translation from the original German of von Harnack's Das Evangelium vom Fremden Gott. I will put the original German first. Any help to fix the translation is welcomed:
Die Marcioniten - das sind die Anhänger des M., die vor den Bardesaniten auftraten und eine Gemeinde bildeten, die den Christen näher steht als die Manichäer und Bardesaniten. Sie behaupten, daß die beiden ewigen Prinzipien das Licht und die Finsternis seien und daß es ein drittes Wesen gebe, welches sich ihnen beigemischt habe. Sie behaupten ferner, daß Gott der Erhabene rein sei von aller Art Bösem und (nichts zu tUn habe) mit der Erschaffung aller Dinge insgesamt, die von schädlichen Bestandteilen nicht frei ist, während er darüber erhaben ist. Sie sind aber verschiedener Meinung darüber, was das dritte Wesen sei. Einige sprechen sich dahin aus, daß es das Leben d. i. Isa (Jesus) sei, andere behaupten, daß Isa der Gesandte dieses dritten Wesens sei, der die Dinge auf dessen Befehl und vermittelst dessen Macht geschaffen habe. Alle dagegen stimmen darin überein, daß die Welt etwas Neuerschaffenes sei und daß die schaffende Hand sich darin nicht verkennen lasse (? ?). Darüber lassen sie keinen Zweifel zu. Sie behaupten ferner, daß, wer fette Fleischspeisen und berauschende Getränke vermeide, zu Gott sein ganzes Leben hindurch bete und ununterbrochen faste, den Stricken des Satans entgehe. Die Berichte, die dem M zugeschrieben werden, weichen sehr voneinander ab und sind vielen Schwankungen unterworfen.- Die Marcioniten haben ihre eigene Schrift, mit der sie ihre Religionsbücher schreiben. M. verfaßte ein Buch, das er Evangelium nannte, und seine Schüler eine Anzahl andere, die Gott allein zu finden weiß. Sie verkriechen sich hinter das Christentum und halten sich zahlreich in Chorasan auf. Ihr Kultus ist ebenso bekannt wie der der Manichäer
The Marcionites -. These are the followers of Marcion, which occurred before the Bardesaniten and formed a community that is closer to the Christians as the Manichean and Bardesaniten They claim that the two eternal principles are the light and darkness and that it a third being admit that had they added. They say also that God was the exalted pure from all types of evil and (to do nothing to) with the creation of all things as a whole, the harmful constituents is not free, while about is raised. But they are different opinions about what is the third sector. Some suggestions are to the effect that there life is di Isa (Jesus), others claim that Isa was the ambassador of this third system and of the things on which command means and has created its power. All however agree that the world is something new creative and that the creating hand, do not support it ignore (?). Moreover, they leave no doubt. They say also that whoever fat meat and intoxicating drinks avoid, pray to God all his life and continuously chamfered, the bonds of Satan's escape. The reports that the Marcion are attributed to soft, widely and have many fluctuations .- The Marcionites have their own script, with which they write their religious books. Marcion wrote a book which he called the Gospel, and his students do a number of other, related to God alone. They hide behind Christianity and remain abundant in Khorasan. Their cult is just as known as the Manichean.