I think I might have made some progress on this subject. I will let other members of the forum judge whether I am merely arguing on behalf of pre-existent ideas.
I can't deny that I suspect that Against Marcion Book 4 goes back to a Greek original. That's a pet project or whatever you want to call it. I have notied that the discussion of Jesus's descent seems rather sudden and out of place in a discussion of Luke 3:15. What if the original text followed from what is preserved in the previous chapter? Let's put the discussion of Luke 3:15 in its original context:
Marcion lays it down that there is one (alium esse) Christ who in the time of Tiberius was revealed by a god formerly unknown, for the salvation of all the nations (a deo quondam ignoto revelatus sit in salutem omnium gentium); and another who is destined by God the Creator (alium qui a deo creatore) to come for the re-establishment of the Jewish kingdom (restitutionem Iudaici status). Between these he sets up a great and absolute divide (scindit), such as that between justice and kindness, between law and gospel, between Judaism and Christianity. From this will also derive our prescription (Hinc erit et nostra praescriptio), by which I lay it down that the Christ of a different god has no right to have anything in common with the Creator; and again, that Christ must be adjudged to be the Creator's if he is found to have administered the Creator's ordinances, fulfilled his prophecies, supported his laws, given actuality to his promises, revived his miracles, given new expression to his judgements, and reproduced the lineaments of his character and attributes. I request you, my reader, always to bear in mind this undertaking, this prescription (, and begin to be aware that Christ belongs either to Marcion or the Creator.
In the fifteenth year of the principate of Tiberius he proposes (God? some ms = deum others eum) came down into Capernaum, a city of Galilee—from the Creator's heaven, of course, into which he had first come down out of his own.1 Did not then due order demand that it should first be explained how he came down from his own heaven into the Creator's? For why should I not pass censure on such matters as do not satisfy the claims of orderly narrative, <but let it> always tail off in falsehood? So let us ask once for all a question I have already discussed elsewhere (ecquid ergo ordinis), whether, while coming down through the Creator's territory and in opposition to him.
The Latin root of scindit is scindo which is the equivalent of the Greek σχίζω. Is it coincidence that during the baptism narrative a cosmic 'tear' is mention with the descent of Christ:
καὶ εὐθὺς ἀναβαίνων ἐκ τοῦ ὕδατος εἶδεν σχιζομένους
τοὺς οὐρανοὺς καὶ τὸ Πνεῦμα ὡς περιστερὰν καταβαῖνον εἰς αὐτόν [Mark 1.10]
McDonald notes that the parallel use of the terminology is followed by Matthew with respect to the tearing of the veil but not the baptism. https://books.google.com/books?id=SbpVq ... rk&f=false
It is very curious especially given Luke's preservation of Jesus announcing that he brings 'division' to the world. If we understand that Marcion understood Christ - not Jesus - came from heaven and that a tear or a schism took place in the heavens this understanding might still be lurking in the fragments of the ur-text in Against Marcion Book 4.
But then just when you begin to give up hope to discover a path ... it appears.
Snow notes that the context for Mark 1:10's vision of the heaven's rending at the appearance of Christ is Isa 64.1 https://books.google.com/books?id=mzNQD ... ns&f=false
Oh, that you would rend the heavens and come down,
that the mountains would tremble before you!
The Hebrew is unspectacular:
לוּא-קָרַעְתָּ שָׁמַיִם יָרַדְתָּ, מִפָּנֶיךָ הָרִים נָזֹלּוּ.
But the Targum perhaps provides a clue:
כַד שַלַחת רֻגזָך בְאִשָתָא אִתמְסִיאַת יַמָא מַיָא מְלַחְכָא אִשָתָא לְהוֹדָעָא שְמָך לְסָנְאֵי עַמָך מִן קְֹדָמָך עַמְמַיָא זָעוּ
As Murray notes the root here of שַלַחת means 'naked' and 'sent' (apostle). https://books.google.com/books?id=ONJlu ... em&f=false
Christ is undoubtedly related to the ultimate appearance of the apostle Paul.
“Finally, from so little sleeping and so much reading, his brain dried up and he went completely out of his mind.”
― Miguel de Cervantes Saavedra, Don Quixote