The most prevalent tradition has it that the name Mu˓tazila was used to refer to someone or a group of people who withdrew (i˓tazala, from which the term Mu˓tazila derives) from an eighth-century circle of majority on whether a grave sinner was a believer or unbeliever. Later on, the term Mu˓tazila was used to designate a school of Islamic theology that follows certain rules known as the five principles (al-usul al-khamsa).
This theological school is one of the most progressive schools in the history of Islamic theology and has to a high degree contributed to the development of Islamic thought. This school is theological due to its starting point that God is unquestionably regarded as the ultimate source of its worldview. However, its emphasis on the use of reason in its theological quest and its assimilation of some Greek ideas and methods of arguments with Islamic principles have contributed to a great extent to the development and flourishing of rationalism in early Islamic thought.
The seeds of Mu˓tazilite views disseminated by its early figures such as Wasil b. al-˓Atta˒, ˓Amr b. ˓Ubayd, and Abu l-Hudhayl eventually got formulated and adopted as five Mu˓tazilite principles. The principle of unity (tawhid) suggests God's unity against any resemblance to Him. Under this principle, Mu˓tazilites deny the eternity of the Qur˒an, God's attributes, and any form of anthromorphism. The principle of justice (˓adl) is associated with the theory of determination (qadar), in which it is maintained that God is just and that human beings are free to choose and to act. The principle of promise and threats holds that God is truthful and bound in keeping His promise of heavenly reward and threat of hellfire. As He promised, for example, a great sinner will forever be in hell unless s/he repents. The principle of intermediate position (manzila bayn al-mazilatayn) indicates that a Muslim who does great sin is regarded as neither a believer (mu˒min) nor an unbeliever (kafir). The principle of commanding the right and forbidding the wrong (al-amr bi al-ma˓ruf wa al-nahy ˓an al-munkar) instructs every Mu˓tazilite to apply this principle to the social world when he or she has the power to do it.
Hourani, George F. Islamic Rationalism: The Ethics of ˓Abd al-Jabbar. Oxford, U.K.: Clarendon Press, 1971.
Martin, Richard C., and Woodward, Mark. Defenders ofReason in Islam: Mu˓tazilism from Early School to Modern Symbol. Oxford, U.K.: Oneworld, 1997.