A caliph allegedly banned non-Koranic study because philosophy would undermine Islam’s truth

Evidence

Their wise men began to execrate the perversity of their law. Since this law could be eliminated either through the books of the prophets, by the law of Moses, or even by the veracious books of the philosophers, therefore the Caliph of Baghdad ordered that nothing should be studied in Baghdad except the Koran. For this reason, we find that they know very little about the truth of theology or the subtlety of philosophy. Nevertheless, their wise men put no faith in the sayings of the Koran, but deride it in secret. In public, though, they honor it, on account of their fear of others. — John V. Tolan, Saracens, 1252

Categorization

• XREF: This is the medieval root of the modern trope — in the vault’s Anidjar/Aziz materials — that Islam suppresses free thought and critical inquiry; it also licenses the ‘secretly disbelieving Muslims’ stereotype.
• SEED: Angle: tracing the ‘Muslims secretly doubt their own religion’ trope from Riccoldo’s Baghdad fantasy to contemporary suspicions of Muslim ‘double loyalty’ to faith.