Ash'ari in the context of "Muslim sects"

Ibn Rushd (14 April 1126 – 11 December 1198), Latinized as Averroes, was an Andalusian polymath and jurist who was proficient in a variety of intellectual fields, including philosophy, theology, medicine, astronomy, physics, psychology, mathematics, neurology, Islamic jurisprudence and law, and linguistics. The author of more than 100 books and treatises, his philosophical works include numerous commentaries on Aristotle, for which he was known in the Western world as "The Commentator" and "Father of Rationalism".

Averroes was a strong proponent of Aristotelianism; he attempted to restore what he considered the original teachings of Aristotle and opposed the Neoplatonist tendencies of earlier Muslim thinkers, such as al-Farabi and Avicenna. He also defended the pursuit of philosophy against criticism by Ash'ari theologians such as Al-Ghazali. Averroes argued that philosophy was permissible in Islam and even compulsory among certain elites. He also argued scriptural text should be interpreted allegorically if it appeared to contradict conclusions reached by reason and philosophy. In Islamic jurisprudence, he wrote the Bidāyat al-Mujtahid on the differences between Islamic schools of law and the principles that caused their differences. In medicine, he proposed a new theory of stroke, described the signs and symptoms of Parkinson's disease for the first time, and might have been the first to identify the retina as the part of the eye responsible for sensing light. His medical book Al-Kulliyat fi al-Tibb, translated into Latin and known as the Colliget, became a textbook in Europe for centuries.

Mu'tazilism (Arabic: المعتزلة, romanized: al-muʿtazila, singular Arabic: معتزلي, romanized: muʿtazilī) is an Islamic theological school that appeared in early Islamic history and flourished in Basra and Baghdad. Its adherents, the Mu'tazilites, were known for their neutrality in the dispute between Ali and his opponents such as Mu'awiya after the death of the third caliph, Uthman. By the 10th century the term al-muʿtazilah had come to refer to a distinctive Islamic school of speculative theology (kalām). This school of theology was founded by Wasil ibn Ata.

The later Mu'tazila school developed an Islamic type of rationalism, based around fundamental principles: the oneness (Tawhid) and justice (Al-'adl) of God, human freedom of action, and the creation of the Quran. The Mu'tazilites are best known for rejecting the doctrine of the Quran as uncreated and co-eternal with God, asserting that if the Quran is the literal word of God, he logically "must have preceded his own speech". This went against a common Sunni position (followed by the Ashʿarī and Māturīdī) which argued that with God being all-knowing, his knowledge of the Quran must have been eternal, hence uncreated just like him. The school also worked to resolve the theological "problem of evil", arguing 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; consequently evil must be regarded as something that stems from errors in human acts, arising from man's divinely bestowed free will.The Mu'tazila opposed secular rationalism, but believed that human intelligence and reason allowed Man to understand religious principles; that good and evil are rational categories that could be "established through reason".

Islamic neo-traditionalism is a contemporary strand of Sunni Islam that emphasizes adherence to the four principal Sunni schools of law (Madhahib), belief in one of the Ash'ari, Maturidi and Athari creeds (Aqaid) and the practice of Sufism (Tasawwuf), which Islamic neo-traditionalists consider to be the Sunni tradition.

Qadariyyah (Arabic: قَدَرِيَّة, romanized: Qadariyya), also Qadarites or Kadarites, from qadar (قدر), meaning "power", was originally a derogatory term designating early Islamic theologians who rejected the concept of predestination in Islam, qadr, and asserted that humans possess absolute free will, making them responsible for their actions, justifying divine punishment and absolving God of responsibility for evil in the world. Originally, the Qadarites also reject belief in the prior knowledge of God, and they deny that God wrote the decrees concerning His creation before He created the heavens and the earth; Consequently, their belief goes against the teachings of Sunni Islam. Some of their doctrines were later adopted by the Mu'tazilis and rejected by the Ash'aris. They argued that evil actions of human beings could not be decreed by God, as they would have to be if there was no free will and all events in the universe were determined by God.

Qadariyyah was one of the first philosophical schools in Islam. The earliest document associated with the movement is the pseudoepigraphical text Risala attributed to Hasan al-Basri, which was composed between 75 AH/694 CE and 80/699, though debates about free will in Islam probably predate this text. According to Sunni sources, the Qadariyah were censured by Muhammad himself by being compared to Zoroastrians, who likewise deny predestination.