I am wondering what were the reasons & effects for the revival of Sunni orthodoxy during the 12th/century?
You asked about the reasons and the effects of the Sunni orthodoxy revival during the 12th century. The information I have provided below first describes the Sunni tradition, and then I have provided for you an excerpt from a book that answers the questions of why and of what the lasting effects are.
The Sunni tradition is one of the two main sectarian divisions in Islam (the other being Shi'a). A number of important principles govern the Sunni tradition.
1. The Prophet and his revelation are of foremost authority.
2. In order for the Qur'an to be used as a basis for sound judgement for subjects under dispute it is necessary to take sound hadiths into account.
3. Qur'anic verses should be interpreted in the context of the whole of the Qur'an.
4. In understanding the Qur'an rational thinking is subordinate to revelation. If the Qur'an or the Sunnah of the Prophet offers a clear judgement on anything, the Muslim is obliged to follow this judgement. If there is no clear judgement about anything in the Qur'an, then it is necessary to make a rational opinion (known as Ijtihad) which is consistent with Qur'anic teaching.
5. The first four caliphs were the legitimate rulers of the early community.
6. Faith and deeds are inseparable.
7. Everything occurs according to the divine plan.
8. Allah will be seen in the life after death.
The Sunni tradition also emphasizes the importance of religion in the formation of public policy. This emphasis has, according to Sunni-Muslim scholars, given rise to two interrelated processes: the supremacy of the Shari'a and the sovereignty of the Islamic community. According to the Sunni tradition, if Islam is a legalistically oriented religion, concerned with the organization of human society, it follows that religious teaching must concern itself with matters of marriage and divorce, inheritance and ownership, commercial transactions and contractual dealings, government, banking, investment, credits, debts and so on. The proper execution of these contractual matters according to the principles of the shari'a based on the Qur'an and the Sunnah of the Prophet constitutes an important part of the way to salvation.
The following excerpt from Peter von Sivers book The History of Islam in Africa,© 2000, Ohio University Press, should help give you some insight into why there was a revival of the Sunni orthodoxy and what the effects of that revival were.
The Formation and Dominance of Sunni Orthodoxy (700-1800)
The promotion of a specific religion as orthodoxy by an empire is a relatively late phenomenon in world history. The first to be so promoted was Zoroastrianism, adopted by the Persian Sasanids (224-651 C.E.) as their state religion. Islam, supported by the Arab caliphal dynasties of the Umayyads and 'Abbasids as the religion of their far-flung empire after their rise in the seventh century C.E., was the most recent. In all cases--be it Zoroastrianism, Buddhism, Confucianism, Christianity, or Islam--the endorsed religion was attributed to a founding figure who preceded the empire. These religions went through more or less extended formative phases in the empires before they crystallized into dominant orthodoxies and a variety of heterodoxies that either died out or became marginal.
Christianity, the state religion of the Roman-Byzantine Empire from the fourth century C.E., was in the last stage of its doctrinal evolution toward imperial orthodoxy when the Arabs occupied Byzantine Syria and Egypt in 634-55. It appears that it was the still unsettled question of a Christian orthodoxy for the Byzantine Empire that inspired the rulers of the new Arab empire to search for their own, independent, religion. Caliph 'Abd al-Malik (685-705) was the first to leave us an idea of the beginnings of this new religion in the inscriptions of the Dome of the Rock in Jerusalem (691). He called this new religion "Islam" and proclaimed its superiority over Christianity.
During the early seventh century, Byzantium had been racked by the controversy between the patriarchs of Constantinople and Alexandria over the orthodox interpretation of Christology. Constantinople advanced the doctrine of Christ's mysteriously double nature, divine as well as human (the Nicene Creed). Alexandria insisted on the more rational doctrine of God's single, divine nature descending into the human form of Jesus (Coptic monophysitism). While the emperors vainly sought to impose a compromise formula, the caliphs took advantage of their disarray. "Do not speak of three (gods)," warns one of the inscriptions on the Dome of the Rock, disposing of Christology altogether. Islam was presented as the new, superior religion, built on a clear, rational separation between a single, non-Trinitarian God and the world.
Proclaiming a new religion was one thing; turning it into an orthodoxy was another. Inevitably Islam underwent the same process of rancorous divisions as did Christianity before orthodoxy eventually emerged. The rancor began over the nature of the caliphate and its ability to define doctrine. The caliphs interpreted themselves as representatives (caliphs) of God, and said that their decisions, therefore, were divine writ. On the other hand, it was claimed that because the divine word was laid down (probably by the 700s) in scripture, in the Quran, no one was privileged over anyone else to make law; the interpretation of scripture was held, in this view, to be a collective right.
At first the caliphs continued to issue laws and formulate dogma as they saw fit, but in the ninth century the tide turned. Pious critics, claiming to speak for all Muslims, increasingly gained the initiative. What had hitherto been caliphal law now was turned into the alleged precedents ( hadiths ) established by the prophet Muhammad. Ad hoc dogmas promulgated by the caliphs were replaced by a progressively systematic theology formulated by the ...
This solution examines the reasons & effects for the revival of Sunni orthodoxy during the 12th century.