The Qadariyya were a short-lived theological movement during the Marwanid Period (684-750) of the Umayyads. According to Ibn Abi Hatim, Ibn Asakir, and Al-Mizzi, the movement followed Ma’bad b. ‘Abdullah b. ‘Ukaym al-Juhani (a muhaddith and the son of a Companion of the Prophet ﷺ ) in affirming the concept of Free Will, or Qadar, as opposed to Divine Determinism, known as Jabr.

It is likely that Qadariyya theology was inspired by the Christian debates in Syria at the time of the Umayyads, and indeed, a Christian named either Sawsar or Susan (or Susnoya?) is thought to have taught the creed to Ma’bad b. Abdullah b. ‘Ukaym al-Juhani. For example, John of Damascus wrote that ‘God is not the cause of evils’ and arguments around free will were strong among Christians. They were classed under the term Murju’ites, the principal belief of which was that judgement of sinners’ fate is deferred to God.

We do not know the extent of popularity the movement had. A student of Ma’bad, Ghaylan al-Dimashqi, was a respected bureaucrat under Caliph ‘Umar b. ‘Abd al-‘Aziz (717-720), was executed for spreading his doctrine. We also know that there was a sizable amount of Qadarriya that under Hisham ibn ‘Abd al-Malik (724-743), a group was exiled to Dahlak (from Al-Tabari, Tarikh 2:1777). As Umayyad state doctrine was built around the idea that the Caliph’s doing was God’s will, a position rooted in part in predestination, the Qadari creed appealed to those with rebellious intent, and between 744-747 Third Fitna, the Qadariyya put their weight behind Yazid b. Al-Walid, and faded into irrelevancy following his defeat. It is notable also that a forged, inauthentic text attributed to Al-Hasan Al-Basri, “Qadarite Epistle to Caliph ‘Abd al-Malik b. Marwan” also existed.

During this time, Kalam (a style of theological argumentation where someone asks questions and reduces an opponent’s position to meaningless alternatives), and ‘Ilm al-Kalam emerged. Some of their views would return as Mu’tazilite Creed during the Abbasid era.

Sources:
Alexander Treiger “Origins of Kalam” in the Oxford Handbook of Islamic Theology
Steven C. Judd “The Early Qadariyya” in the Oxford Handbook of Islamic Theology