Here is what is developed in Curt Peters, Das Diatessaron Tatians (1939) partly his own discoveries, partly from previous studies.(a) The Diatessaron is founded on the Gospel of the Hebrews and probably includes the whole text of it. The reason Epiphanius confused the Diatessaron with the Gospel of the Hebrews is that it WAS the Gospel of the Hebrews with additions, and might even have been commonly called the Gospel of the Hebrews.
(b) It was not named the Diatessaron by its author. That name comes from the later WRONG GUESS that it was made by combining the Canonical Four. The older name is Diapente, “product of five”, that is, the Gospel of the Hebrews as base, with Matthew Mark Luke John fitted in. Even this name is not original.
(c) Tatian changed the dialect from Western Aramaic to International Standard Eastern Aramaic, i.e. Syriac.
(d) The wording of the Diatessaron is far superior in literary quality and in clarity and in logic to the wording of the Canonical Four, at all levels, from paragraph to sentence to phrase to choice of single word. I take this to mean it was NOT re-worded from the Canonical Four, but is an original long Gospel similar to the source from which the Canonical Four were excerpted and re-worded.
(e) None of the extant extensive textwitnesses give us the pure text of the Diatessaron. All have been adapted to the Canonical Four. This applies to the Syriac quotations, and to the Syriac text from which the Arabic was translated, and the Latin text from which the Dutch was translated. The original wording can,, however, be seen in some fragments in the European transmission. I add that it was this adapted text that made people guess that the book was a combination of the Canonical Four. I add further that I doubt whether ANYTHING in the original Diatessaron was lifted from the Canonical Four, except where something was missing in the Gospel of the Hebrews. Even then, I think it was taken from the ORIGINAL john used by the Valentinians and so on. Peters adds that the original wording can be reconstructed verse by verse by comparing the extant Syriac quotations, the Arabic, the Dutch, quotations in Armenian, and quotations in some mediaeval Latin works. The rule is, whatever is furthest from the Canonical Four is closest to the Diatessaron. Imagine that the Arabic is not the Diatessaron, but the Diatessaron altered in content and wording to agree with the Canonical Four.
(f) The Diatessaron was accepted immediately in Rome and translated immediately into Latin and vigorously promoted.
(g) I add that it is hard to see Tatian as a follower of Justin. Why would a follower of Justin promote the Gospel of the Hebrews against the Canonical Four? Have we got a true picture of Tatian? Or is it a fiction designed to hide his true affiliations?
