The seventh Caliph whose reign marked the beginning of the Abbasid decline. When al-Mamun's father, Harun al-Rashid, died, in 809, he recognised his stepbrother Amin as the Caliph, according to his father's wishes. However when Amin declared that his son and not al-Mamun would inherit the Khilafat after him, a fight broke out between the brothers in which Amin was killed and al-Mamun came to power in 813. When al-Mamun emerged as the victor and began his reign (813 - 833), it was clear that there were two main power blocs in the empire. One was the aristocratic circle of the court and the other, egalitarian and 'constitutionalist' bloc, based on Shariah. During his regime the balance of power shifted from the Arabs to the non-Arabs. Caliph al-Mamun was aware of the fragility of his rule. Caliph al-Mamun's reign had started with a civil war in Kufah and Basrah (814-15) and a kharajite revolt in Khurasan. He, being an intellectual, brought peace by being drawn to the rationalism of the Mutazilah and realised that movement of ahl al-hadith, which insisted that the divine law was directly accessible to every single Muslim, was not compatible with absolute monarchy. Muatazilizm that had flourished in Caliph al-Mamun's reign believed that the Qur'an was created and, therefore, not eternal. If it was created it could, consequently, be modified to suit different times. This position suited Caliph al-Mamun but was resisted by Imam Hanbal, who believed that no one should be allowed to tamper with the utterances of Hazrat Muhammad, peace be upon him, and that the acceptance of Sunnah in its entirety was the 'sine qua non' of true Islam. Caliph al-Mamun was famous for his patronage of scholars and poets. He encouraged the study of Greek philosophy and sent his envoys as far afield as Constantinople in search of as many Greek manuscripts they could find, and to establish in Baghdad a centre devoted to translation. Libraries and centres of learning had been established and by far the most famous was Caliph al-Mamun's House of Wisdom (bayt al-hikma), founded in 833. Had it not been for Caliph al-Mamun's dream, his foresight and generosity, the great chain of learning - from Athens to Alexandria to Antioch and Edessa, to Gondeshapur to Baghdad to Toledo - would never have been completed, and without the dedication of later Arabs, Europe and the rest of the world would have been incomparably poorer. All these places, Baghdad included, were cosmopolitan cities, international and ecumental centres, where ideas were free to move around, untrammelled by censorship or religious bigotry.