The belief in eternal truth drove systematic misreading of Islam.

Evidence

Truth was eternal, and the structure of God’s plan was rational and constant; the revered writings of old remained their surest guide. Error, apparently multifarious, nevertheless reflected the constant opposition between God and Satan. These are the principles behind all the willful misunderstandings and distortions of Islam examined in the chapters that follow. — John V. Tolan, Saracens, 162

Categorization

• ADDENDUM: Builds on the article about how moral panics need an interpretive frame; here the eternal-truth frame supplies exactly that template for reading a new religion as error.
• XREF: connects to: Ketton deliberately obscured Islam’s claim to universal prophethood; Each religion saw the other as a corruption of its own truth. — Norman Daniel, Islam and the West, 1039; False statements about Islam persisted for centuries because community good seemed to require them