Muʿtazila (Arabic: المعتزلة) refers to a group of Sunni Muslims who famously consider the Intellect (al-'aql) to trump, or be prior to, the Tradition (al-naql). The Mu'tazila are closer than other Sunni theologians to Imami theologians.
The Mu'tazila believed that the theoretical reason should evaluate what we learn through divine revelation. This principle cultivated in some theses in the intellectual system and religious beliefs of the Mu'tazila, providing them with a particular conception of monotheism and divine justice. Thus, they tried to interpret away the religious texts which were apparently at odds with the reason. For example, they denied, and interpreted away, the possibility of seeing God which is apparently mentioned in some religious texts, because according to the reason, it is not possible to see without a space and a spatial direction, and since God is beyond any space and direction, it is not possible to see Him in this world, nor in the afterlife. Some Mu'tazili beliefs are explicitly contrary to the ones agreed upon by other Sunni Muslims.
The Mu'tazila are considered to be one of the first people in Islam who tried to explain and justify religious doctrines by means of reason and intellectual analysis.
The Mu'tazila constitute a theological denomination formed in the early 2nd/8th century. The first leader of this group was Wasil b. 'Ata'. He proposed a new theory about the committer of a Major Sin, which was contrary to that of Murji'a and Khawarij. According to his theory, the committer of a Major Sin is not, contrary to the view of Murji'a, a believer, nor an unbeliever, as Khawarij maintained. Rather, such a person is only fasiq (a violator of Islamic rulings) and has a place in between a believer and an unbeliever.
According to some reports, this group is called "Mu'tazila" (which literally means "isolated") because their founder, Wasil b. 'Ata', isolated himself from, and abandoned, Hasan al-Basri's circle and founded his own school of thought.
Some scholars take the Mu'tazila to be in continuity with the political I'tizal (isolation). A group of Sahaba and Tabi'un who refrained from making any judgments concerning, and any supports of, either party at wars in the period of Imam 'Ali (a) was called "Mu'tazila" (since they had isolated themselves from such conflicts). Other scholars believe that Mu'tazila are natural successors of Qadariyya, because the two groups shared many beliefs.