18. Tertullian wasn't the original author of the material in Adversus Marcionem

Tertullian is universally acknowledged to be our 'best source' for information about the Marcionite canon.  The reason is simple.  He seems to go through line by line at times important sections of the Marcionite interpretation of the gospel which was common to both traditions.  Epiphanius does very much the same thing, but the Panarion is much later (= late fourth century CE).  Since the Latin text of Adversus Marcionem (= Against Marcion) seems to take up Irenaeus's claims that Marcion corrupted 'according to Luke' it is generally understood to confirm that position.  Why else would Tertullian agree that the Marcionite gospel is a corrupt version of Luke unless it were true?  But such a position ignores the reality of what stares us in the face at the very beginning of the text.

At the start of Book One hanging almost like a warning notice to the reader the following bold pronouncement is made:

Si quid retro gestum est nobis adversus Marcionem, iam hinc viderit. Novam rem aggredimur ex vetere. Primum opusculum quasi properatum pleniore postea compositione rescideram. Hanc quoque nondum exemplariis suffectam fraude tunc fratris, dehinc apostatati, amisi, qui forte descripserat quaedam mendosissime et exhibuit frequentiae. Emendationis necessitas facta est. Innovationis eius occasio aliquid adicere persuasit. Ita stilus iste nunc de secundo tertius et de tertio iam hinc primus hunc opusculi sui exitum necessario praefatur, ne quem varietas eius in disperso reperta confundat.

Whatever in times past we have wrought in opposition to Marcion, is from the present moment no longer to be accounted of.  It is a new work which we are undertaking in lieu of the old one.  My original tract, as too hurriedly composed, I had subsequently superseded by a fuller treatise. This latter I lost, before it was completely published, by the fraud of a person who was then a brother, but became afterwards an apostate. He, as it happened, had transcribed a portion of it, full of mistakes, and then published it.  The necessity thus arose for an amended work; and the occasion of the new edition induced me to make a considerable addition to the treatise. This present text, therefore, of my work--which is the third as superseding the second, but henceforward to be considered the first instead of the third--renders a preface necessary to this issue of the tract itself that no reader may be perplexed, if he should by chance fall in with the various forms of it which are scattered about.

No matter how we try to get around matters here, this Latin editor is saying (a) that Adversus Marcionem was re-written at least three times and (b) at least one version of the text passed under the name of someone other than Tertullian.

Why is this interesting?  To start with, the idea that there existed many different versions of the argument against Marcion's gospel helps explain another important anomaly - at the deepest layer of the text, the author is not comparing Marcion's text to 'according to Luke.'  This only came with Irenaeus's introduction of Luke's gospel at the end of the second century.  It turns out that at the deepest layer of Adversus Marcionem we find another author besides Tertullian using a 'gospel harmony' which 'mixed' the sayings of Matthew and Luke in particular.  This means that the 'Luke layer' likely developed at the turn of the third century and the 'gospel harmony' layer developed at least a generation earlier.

Here is the critical discovery of the 'super gospel' vs 'super gospel' layer to Adversus Marcionem Book Four.  The Latin text notes that in 'the gospel':

"Because," says (Jesus), "He is kind unto the unthankful and to the evil." (Luke 6:35) Well done, Marcion! How cleverly have you withdrawn from Him the showers and the sunshine. (cf. Matt 5:45) [Tertullian Adv Marc 4:17]

It has long been noted that Tertullian assumes from his gospel that Luke 6:35 and Matthew 5:45 followed one another but Marcion 'erased' Matthew 5:45.  This order doesn't manifest itself in any of our gospels.  The situation develops with respect to a 'gospel harmony' which can be traced back to Justin.

Tertullian agrees with Justin, against Matthew, in regard to the sun and rain. While in Matthew the sun shines over the evil and the rain falls on the just, Justin and Tertullian have the rain fall on the evil and the sun shine on the just. This linkage is intriguing. A. J. Bellinzoni, who has examined harmonizations in Justin's corpus, states: "That this harmonization of Luke 6:36 and Matthew 5:45b was not peculiar to Justin but was rather a written source in common circulation in the early church appears evident not only because it is repeated in both Apol. 15:13 and in Dial. 96:3 but more especially because Lk. 6:36 and Mt. 5:45b occur together in six of the patristic passages already quoted above (see p. 11)."

This underscores the fact that Adversus Marcionem Books Four and Five was originally written by someone with a Diatessaron or a single long gospel which featured readings, commonly associated after Irenaeus with 'Matthew, 'Mark' and 'Luke.'  At some point after its original publication the text was altered to make it reflect an entirely knew textual criticism paradigm (i.e. Irenaeus's Marcion corrupted Luke). Now we can finally understand why Galatians is listed first (it was first in the canon of Diatessaron users in the east like Ephrem and others). This also explains why the author so often accuses Marcion of deleting things which only appear now in Matthew.