The concept is that western Roman Christianity was always quintessentially Marcionite until eastern Jewish Christianity asserted itself in the West in the latter half of the second century. The catholicization process won out in the West, and church fathers and orthodoxizers needed to create an apostolic lineage for Rome through Peter. Thus, the Marcionite nature of western Christianity needed to be placed in a virtual container, a historical strawman, to allow for Rome to have always been catholic. The Roman Catholic history distorts the second century with this highly inaccurate portrayal of what is called Marcionism. In fact, Tatian's Diatessaron is the historically real "Evangelion of the Lord", but this obvious connection is lost due to the false history of Marcionism needed to paint Rome as forever catholic.
Here is why the Diatessaron is similar to Marcion's Evangelion:
- Instead of using the four gospels, a single authoritative gospel is used.
- Elements of the four gospels are changed, edited or redacted by the prerogatives of the author.
- Later in the catholicization process, there is a distinct emphasis on using "separate" gospels and not using the harmonized text. An exactly parallel trend that applies to the Diatessaron and Marcion's gospel.
However, the conventional view of Marcionism via Catholic history makes such a comparison a bit to outstanding to be believable. This is reconciled by considering a reasonable interpretation of history against Catholic bias. There is very little evidence of the Roman papacy as an institution in the first century, nor any particular connection to Peter. Western Christianity was philosophical and Pauline. Eastern Christianity was Jewish, and eschatological. What we call Marcionism, what we understand it to be, what Marcion's Gospel was has been highly distorted. Marcion's Gospel is not secretly exactly the Diatessaron. Rather, where the historical impact of the Diatessaron is inconvenient, it is called Marcion's Gospel.
Here is a reconstruction of second century catholicization:
- The Kitos war ends messianic Jewish zealotry as Rome defeats two distinct Jewish uprisings, of two different natures, one in the West and one in the East.
- The eastern Jews react to this defeat by introducing the Book of Elchasai, with direct lineage to the Nazorean, Transjordanian and Assyrian baptizer cults. It is primarily eschatological, but also follows the law and insists on righteous works.
- The western Jewish tradition inherits the Philonism of Jewish aristocrats (Alexandrians, Cyrenian merchants, Sadducees, Herodians), which does not require adherence to law, and is heavily philosophical.
- After 135AD, Bar Kokhba, western Roman Christians seek distance from Judaism. This leads to the writing, within a common temporal and geographical locus (Rome), of the four gospel (there may have been earlier source texts). Western, Roman Christianity becomes somewhat anti-Jewish.
- Tatian, an eastern Christian, travels to Rome and encounters the gospel texts and is impressed by them. Whereas western Christianity uses philosophy for exegesis, eastern Christianity using prophecy, Tatian seeks to use history for Christian exegesis. Tatian appears to be a scholar and philosopher, but of a distinct Babylonian/Assyrian heritage enough to have critical opinions about the inadequacy of western philosophy. He writes the Diatessaron and brings it East.
- The Diatessaron is responsible for two particular outcomes. First, it is associated with the intrusion of Roman Christianity (Gnostic/"Marcionite") into the East. Second, it is associated with historical exegesis.
- Tatian's work inaugurates a process of catholicization, which seeks truth through textual and historical exegesis. Eastern Christianity remains heavily Jewish in spite of western Christianity's anti-Jewish ideas.
- It is the influence of the proto-catholicizing, eastern Jewish Christians using historical exegesis, which blows into the West.
- The influence of East upon West could have been a long and varied process, but takes root in Asia in particular. These formerly "Marcionite" Christians now possess Johannite literature, the Book of Revelations to John, etc.
- As Roman Christianity was quintessentially Marcionite, this new catholicizing locus finds itself surrounded by Marcionites. Missionaries go to Egypt, to Carthage, to Rome and to Gaul. The literature associated with Irenaeus and Tertullian are a product of this eastern seed sprouting in the West.
- As this catholicization process unfolds, under the influence of textual exegesis and a recommitment to Christianity's Jewish roots and eschatological character, West and East are reconciled. The "tension" between the Pauline and Jamesian elements of the New Testament, accommodated by the narrative in Acts, is a result of the catholicization process.
- As Rome becomes fully catholic, whenever and however that finally occurs, the only remaining western, Roman Christians are "Marcionite" converts in the East. In the East, Jewish Christians either become catholic, or else they revert to the emerging rabbinical Judaism.
- When Rome later needs to falsify its history to show it was always catholic, it creates the strawman of Marcionism to conveniently explain that sect's legacy in the West and the East. The catholicizers have insisted on the four gospels, separated, and pushed out the Diatessaron. It is not a favored text, some easterners still associate it with the old Gnostic western influence. Yet, it is also nominally proto-catholic, it cannot be associated with the heretical strawman Rome is attempting to construct. Thus, Marcion's Gospel is born. Marcion's Gospel and Marcionism become a phantom that explains inconvenient history in both East and West. Roman Catholicism, with its eastern, Jewish elements, explains away the fact that western, Roman Christianity was initially, totally and quintessential Marcionite or otherwise Gnostic.