Islamic Studies
Caliphate & Rulers: From the Rightly Guided Caliphs to the Ottoman Caliphate
Which Abbasid Caliph promoted the Mu'tazilah school of thought as state religion?
Explanation
Al-Ma'mun ar-Rashid (198–218 AH) made Mu'tazilah the state religion and had Greek, Persian and Indian books translated into Arabic. This was later reversed by Al-Mutawakkil.
Reference: Islamic Studies - Caliphate & Rulers
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