Imamiyya-Mutazila relationship in the course of time

The relationship between the Imâmiyya and the Mu'tazila goes back to the first half of the IInd/VIIIth century. The middle of the IIIrd/IXth century marked the beginning of a serious competition between Imâmiyya and Mu'tazila. Debates between the members of these two groups and the refutation works they produced against each other testify to this rivalry. In this period, the Mu'tazila, nurtured by philosophy, adopted a rational understanding of religion and advocated absolute transcendence of God and complete free will of man with respect to the topics of God's unicity and justice. The Imâmiyya, on the other hand, adopted a textualist approach in religion and remained resistant to external influences due to the authority of the imams. With respect to the theological topics of God's unicity and justice, the Imâmiyya held onto the principles of "proof (tathbît) without similitude (tashbîh)" and "neither predestination (jabr) nor delegation of power (tafwîḍ)." The relationship between the two schools of thought became tenser from the middle of the IIIrd/IXth century to the period extending to the second quarter of the IVth/Xth. The Mu'tazila's efforts to get closer to the Sunni schools of thought in the post-mihna period played a major role in this tension. As a reaction to this, some Mu'tazilîs joined the ranks of the Imâmiyya. On the other hand, some Mu'tazilî ideas also started to infuse into Imâmiyya thought at a time when the Imâmîs were searching for a safe harbor in the aftermath of the chaos caused by the last imâm's occultation. The Usûlî Imâmîs, who were inclined to accept reason in religion matters, were influenced by these ideas to a large extent; whereas the Akhbârî Imâmîs, who had a text-oriented understanding of religion, were only minimally influenced by them. The Imâmiyya-Mu'tazila convergence, however, reached its peak during the Buwayhid period (320/932-454/1062). Considering this convoluted path of evolution in the relationship between the two schools, they were often regarded to have first become friends and later brothers. In the Buwayhid period, the influence of the Mu'tazila on Usûlî Imâmiyya became stronger and left permanent traces than in the previous period. Even though the Usûlîs were influenced by the Mu'tazila on many topics, they continued to defend their former views on issues such as the imamate, badâ', raj'a and taqiyya and supported them with rational methods of argumentation. On the basis of these developments, Usûliyya can be described as a synthesis of Imâmiyya and Mu'tazila, but with a dominant Imâmî character.