Wikipedia
Mu'tazila ( ) is a school of Islamic theology based on reason and rational thought that flourished in the cities of Basra and Baghdad, both in present-day Iraq, during the 8th–10th centuries. The adherents of the Mu`tazili school—known in English as Mu'tazilites —are best known for their denying the status of the Qur'an as uncreated and co-eternal with God, asserting that if the Quran is God's word, logically God "must have preceded his own speech".
The philosophical speculation of the Mu'tazilites centered on the concepts of divine justice and divine unity. The school worked to resolve the theological " problem of evil", i.e. how to reconcile the justice of an all-powerful God with the reality of evil in the world. It believed that since God is Just and Wise, He cannot command what is contrary to reason or act with disregard for the welfare of His creatures.
Mu`tazilites believed that good and evil were not determined by revealed scripture or interpretation of scripture, but rational categories that could be "established through unaided reason; because knowledge was derived from reason, reason was the "final arbiter" in distinguishing right from wrong. The Mu`tazili school of Kalam posited that the injunctions of God are accessible to rational thought and inquiry, and that it is reason, not "sacred precedent", that is an effective means of determining what is just, and obligatory in religion.
The movement emerged in the Umayyad Era, and reached its height in the Abbasid period. After the 10th century, the movement declined. It is viewed as heretical by some scholars in modern mainstream Islamic theology for its tendency to deny the Qur'an being eternal. In contemporary jihadism, supposed allegations of being a mu`tazili have been used between rivalling group as a means of denouncing their credibility.