If we accept this basic outline...

Although many Western historians of Islam are not Muslims, it would be difficult to determine this from their writings on the first centuries of Islamic history. This is in stark contrast to historians of Judaism and Christianity, who tend to adopt an outsider's approach to their subject when writing in academic contexts (despite often being themselves Jews and Christians). Why the difference? Before turning to answers, it is worth underlining the question. The traditional accounts of Islam's rise tell us that in a remote and isolated region of Arabia (the Hijaz), in a pagan town unaccustomed to monotheism (Mecca), an illiterate man (Muhammad) began to recite verses full of references to Biblical characters and established monotheistic ideas. If we accept this basic outline – and most do – how are we to explain Muhammad's acquaintance with this ideas? To traditionally minded Muslims, the answer is clear: God, via an angel, revealed the verses to him. In fact, it would be hard to be a believing Muslim in the traditional sense without accepting this version of events. Equally, however, Wansborough might argue that it would be hard to accept the broad outlines of the story without being a Muslim (or at least without accepting God's hand in these events), for which reason he argued that Islam and the Quran developed later and elsewhere, where Jewish and Christian ideas were prevalent.

Adam J. Silverstein, Islamic History: A Very Short Introduction.
Oxford University Press