I have been led by evidence to accept that the Marcionites used a Diatessaron. Their original opponents - the sectarians aligned with Polycarp - also used a Diatessaron. The early anti-Marcionite literature which now survives principally in texts copied and developed by Tertullian and Epiphanius developed from a Diatessaron vs Diatessaron tradition. It will be my contention that the 'secret gospel' of Mark was an Alexandrian 'Diatessaron' associated with Ammonius Saccas. The arguments on behalf of this proposition have been developed here over and over again so I don't feel the need to go over them again.
What is important is that we recognize that all 'Diatessaron gospels' were related. We see this most clearly when - for instance - Origen (Commentary on Matthew Book 15), Ephrem and a diverse assortment of authors all acknowledge that the 'Question of the Rich Man' continued into the Rich Man and Poor Man in Hades (= 'Lazarus and Dives' Luke 16:19 - 31). William Petersen wrote about this much studied phenomenon. Yet the most striking reference to this tradition is found in Ephrem's Commentary on the Diatessaron, where obvious parallels and 'affinities' with what is known about 'secret Mark' are hard to ignore.
In discussing Jesus 'love for' the rich man, Ephrem makes clear that Jesus is waiting for the rich man to reciprocate his love (cf. Letter to Theodore III:4,5). Yet perhaps more significantly it is clear that Ephrem's Diatessaron - no less than Origen's Gospel According to the Hebrews - identifies the 'rich man' of Mark 10 with the 'rich man' of Luke 16:19 - 31. In other words, the narrative of the Question of the Rich Man continued in the Diatessaron to the same rich man's 'death' in Hades. We read Ephrem note:
[Through] that which [he said], Good Master, (Mark 10:17) he anticipated our Lord with a gift. But our Lord removed this opportunity for flattery, to show him that it is right to both speak and hear the truth. He looked at him lovingly, (Mark 10:21) so that perhaps through this he might be attracted to draw closer to perfection, through which also the former [commandments] are cultivated. But, because his righteousness was according to the Law - and because it was in the hope of the goods of here [below] that [the former commandments] were cultivated - he trusted in his wealth as the recompense for his righteousness. Wherefore, it is difficult for the rich and for those who trust in this for their riches are the due recompense of their activities. Indeed those who think that riches are a reward for their righteousness are not able to leave them. Lest [the rich man] say, "Even from the beginning he replied to me indignantly and rejected me with some pretext," [the Lord] said to him, One only is good. Is he not therefore good, who is called the Son of the Good One? This is why he looked at him lovingly, so that he might show [the rich man] that it was his own self that he was rejecting. For he is the rich man, who was attired in purple.(Luke 16:19) See, he is a son of Israel, because of what [he said], My father, Abraham,(ibid) and because of, They have Moses and the prophets.(Luke 16:29) [Ephrem, Commentary on the Diatessaron, McCarthy translation p. 233]
It is difficult to understand how anyone can doubt the authenticity of the 'secret Mark' fragment when Morton Smith never acknowledged the underlying connection with the Diatessaron. Indeed he spent hundreds of pages attempting to find a context for the omitted material from Mark without even recognizing the most obvious connection of all - viz. the rich man's 'death' and continuation from Mark 10:17 - 31 to Luke 16:19 - 31 in the Diatessaron tradition.
In fact, even more incredible is the fact that Morton Smith did not even recognize that the Diatessaron inserts the account of Zacchaeus (Luke 19:1 - 11) in the very place where the second addition to Secret Mark mentioned by Clement in the Letter to Theodore. The parallels between the Diatessaron and 'secret Mark' are so consistent and so overwhelming, they are overshadowed only by Clement's own consistent use of Diatessaronic material. As I have said many times over here, I strongly suspect that 'Clement' is one and the same with the shadowy figure of Ammonius Saccas. But that's another distraction completely ...
dating back to conversations with his grandfather, Gaston Frank. "He said we represent one of the last descendants of the Frankist Jewish faith in the world," he muses. "I grew up thinking that our family was something like the Last of the Mohicans."