Mutazilites of eighth and ninth centuries Basra and Bagdad (Iraq) tried to bring rationalism and reasoning in Islam. During that period their theology received patronage from Caliphs also. Mutazilites disagreed that Qur’an is divine and constant and tried to reason out each aspect of Islam. However, in the later part of ninth century, orthodox group got upper hand and put Islam firmly on the foundation of ‘Iman’ only. The orthodox group thoroughly shunned any inquisitiveness or reasoning in Islam labelling these as Haram. It is easy to understand the psychology of the orthodox group. They knew that reasoning would expose the hollowness of Islam and the Caliphate, which was based on Islam, would crumble down. Orthodox group was more anxious for political rather spiritual development which Mutazilites were trying to bring in Islamic world. The Mutazilites were systematically persecuted and there theology was also called blasphemous.
It astonishes one today to know that Muslim world had such Islamic scholars in Mutazilites a millinium back.