For me, the biggest issue is that the Quran has nothing to do with Muhammad and doesn't mention him nor talk about where he lived.
Mi first issue is historical : no Mecca/Medina/Kaba. Therefore no "prophet" producer of the Quran. Elsewhere? Plenty of Jews and Christians, therefore improbable if not impossible as this story would have spread (20 years talking to God, etc)
Once I had realised that, added to no Mecca/Hijra/No Hidjaz but an eastern setting for islam
For me, Eastern emergence of the Quran but composition not necessarily there.
and a Sira totally made up, then I can only come to the conclusion that he never existed, even as an historical figure.
Of course.
The different non muslim sources are currently against me in the sense as some scholars think that they are contemporary to the muslim conquests
Nope, the different non Muslim sources never attests that this guy is alive and kicking. they attests that Arab
literati talk of someone, that's all. Not that Arab
literati have saw/lived/eaten/know very well the guy "Muhammad" they talk about. Never.
and not interpolation from 9th c muslim sources. I am working on that to find the right explanation.
They are contemporary (except Sebeos where there is big issue about his datation) If the different non muslim sources of the 7th c. have been interpolated with Muslims sources of the 9th (like you said) we would have been all the story of "Muhammad" in all the different non Muslim sources of the 7th c. This is not the case (at all). Except Sebeos. But again, Sebeos have a big issue of datation.
I don't buy Altara's thesis that those contemporary non Muslim sources derived their knowledge from arabs who in turn knew this from the Quranic texts that were circulating because
It seems to me that it is a rational and coherent explication.
it is contradicted by the Muhammad of Sebeos
As we do not know the real datation of Sebeos and that exist an issue about it, I set aside this text to be surely of the 7th c. Especially that it is the
only non Muslim source of the 7th c. that recounts what he recounts. The only one. For me, it is not normal ; why the others do not recounts the same thing? There is no reason. The only rational and coherent reason is that it is not a 7th c. text because of the aforementioned reason. That is why I set it aside, for now.
(nowhere does the Quran talk about an alliance with jews)
He does.
and the merchant Muhammad (Sebeos/Jacob of Edessa).
There is no merchant Muhammad in the Quran. There is a someone called Muhammad who was designed as "merchant" by the Muslim narrative (sira, hadith, etc).
Topic: Qur'anic studies today