Medieval Christian writers assumed Muslim doctrine derived from misinterpreted Scripture

Evidence

Alan of Lille took it for granted that Muslim doctrines were based on heretical interpretation of canonical Scripture, and formed his own polemic accordingly. Alexander III wrote similarly, although it is not clear that this pontiff put his arguments forward as acceptable to any and every Muslim, rather than to a single individual, the Sultan of Konya. Much later, Guido Terrena, representative of a highly educated public, used Scriptural authorities in the same way, condemning, for example, the regulations governing the Ramadan fast, by appeal to There were a number of attempts to determine which parts of Scripture Islam could accept. — Norman Daniel, Islam and the West, 315

Categorization

• XREF: Echoes a broader medieval epistemic habit — reading an opponent’s religion as a corruption of your own authoritative texts rather than a distinct tradition — parallel to how Grafting/Infrastructure essay treats received systems as deviating from their source. — connects to: By 1250 the unity-of-God doctrine was common Christian knowledge about Islam; The social character of Islamic practice went unrecognized by medieval Christian writers; Local folk superstitions were mistaken for authoritative Islamic doctrine by medieval critics (+1 more)