The desert environment was blamed for alleged Muslim irrationality and unreliability.

Evidence

The notion that the Oriental was trapped in time is expressed in W. M. L. de Wette’s description of Judaism as a “degenerate, petrified” state, and originates in descriptions of the Orient as an extreme, dangerous, and stagnant region. Such descriptions originate in ancient times. … The condition of the Oriental was believed to be a product of his “desert mode of existence… [that] foster the extremes in emotions so characteristic” of Muslims, which resulted in “blurred perception and the inability to distinguish between truth and falsehood.” Neither Jew nor Muslim could be trusted because of the irrational nature that their wild and uninhibited desert environment engendered. — Sophia Rose Arjana, Muslims in the Western Imagination, 404

Categorization

• XREF: Connects to the reader’s foundational thesis: the Muslim monster manufactured in Western imagination. The desert-climate determinism here is a causal claim explaining how irrationality was attributed to environment rather than encountered reality.
• SEED: The colonial drawing of a Muslim holy man jumping on a sick child to cure him is a vivid concrete image worth citing as evidence of how absurdity was attributed to Muslim religion.