On the Origins of the Diatessaron

It is well established, by Plooij, Boismard, and others, that the author used a Latin translation of a book related to the Diatessaron. Boismard identifies it with the single long Gospel used in the writings attributed to Justin Martyr, and with the ancestor of the Pepys ms. in Middle English (though the Pepys ms. simplifies and condenses the original). The siglum P suggested by Boismard for this text in all its forms is taken from the Pepys ms. If the Latin text puts source references against what corresponds APPROXIMATELY to the Canonical Four, it must be an earlier version of the Diatessaron rather than the Gospel of the Hebrews itself, but it must also be closer to the Gospel of the Hebrews than the Diatessaron (so Boismard). My first guess is that it could be the Gospel of the Hebrews with Tatian’s mark-ups for the composition of the Diatessaron, but that will have to be tested. There is no difficulty in supposing that Tatian had the Canonical Four. The Diatessaron has readings that seem to show the mingling of the text of two or more of these, along with others that can best be explained as coming from a single book not the same as any of the Greek Four. (Though this is very hard to prove conclusively in all places, for obvious reasons). The Syriac Diatessaron with its Latin translation was edited in Rome in about 172 A.D., which is exactly the same time and place the Greek four separate Gospels were edited as a set and promulgated as a set, if Trobisch and others are right.