The secular account of the Quran’s origin is that Muhammad — a gifted, charismatic, morally serious individual with access to Jewish and Christian traditions in seventh-century Arabia — produced the text himself, perhaps sincerely believing it was divinely inspired, perhaps employing the rhetorical conventions of religious authority that his culture recognized. The Quran is, on this account, a human document of great power and influence, but not of divine origin.
This is the hypothesis that needs to be taken seriously, because it is the natural starting point for any critical evaluation. The question is whether the evidence for it is as strong as it appears.
The problem of the literary argument
Muhammad was, by all historical accounts, illiterate — or at minimum, untrained in the literary culture that the Quran exemplifies. The Quran’s literary character occupies a register that has no precedent in Arabic literature: neither poetry nor prose in the conventional sense, combining the sonic and rhythmic qualities of verse with the semantic density and legal precision of elevated prose. The claim that an illiterate man in seventh-century Arabia produced this without divine assistance is a claim that requires as much faith in human literary capacity as the alternative requires in divine communication.
More specifically: the Quran was delivered in fragments over twenty-three years, under conditions of extreme social disruption — migration, warfare, political negotiation, personal bereavement. A human author producing a text with the internal coherence of the Quran under those conditions would represent one of the most remarkable literary achievements in human history. This does not prove divine authorship. But it does suggest that “Muhammad wrote it” is less simple an explanation than it appears.
The consistency of character across twenty-three years
The theological and thematic consistency of the Quran across a twenty-three-year period of delivery is difficult to account for on the hypothesis of single human authorship under pressure. Human beings change. Their preoccupations, their aesthetic sensibilities, their theological emphases shift over time, especially under the pressures Muhammad faced. The consistency of the Quranic voice — its theological register, its literary character, its moral orientation — across decades of fragmentary delivery is either the result of superhuman consistency on the part of a human author, or evidence of a single consistent source that is not human.
The borrowing hypothesis
The alternative secular hypothesis — that Muhammad borrowed from Jewish and Christian sources available to him in seventh-century Arabia — faces specific evidential difficulties. The Quranic accounts of biblical figures often diverge significantly from both biblical and rabbinic sources, in ways that are hard to explain as simple borrowing. Some Quranic material has no parallel in available sources. If Muhammad was borrowing, his selection and modification of the borrowed material was so extensive and so consistent in its modifications as to constitute independent authorship rather than borrowing.
None of this constitutes proof of divine authorship. What it constitutes is a serious challenge to the simple secular explanation — an acknowledgement that the origin of the Quran is not obviously accounted for by any available naturalistic hypothesis, and that the divine authorship hypothesis remains on the table as a live option for anyone examining the evidence honestly.