The Mutazilites belonged to very early school of thought (9th century CE) in Islam which stressed human free will and the justice of God. They attempted to find a "middle path" between the heretical Kharijites and more orothodox beliefs by asserting a "rationalist" method of interpretation.
This rationalist method was, in turn, derived from the philosophical writings inherited from ancient Greece. The Mutazilites urged Muslims to turn away from a strict, legalistic faith and instead transform Islam into a more humanistic religion. The Mutazilites were supported and encouraged by the leaders of the Abbasid Caliphate, but they also threatened the position and traditions of many religious leaders. These in turn eventually succeeding in suppressing the Mutazilite ideas, leaving Greek humanistic philosophy to European Christians to later develop and learn from - leading first to the Renaissance and later to the Enlightenment.
