At the Islamic East, we see that several components of the Renaissance had been present there for centuries: there was immense scientific activity in technical fields such as optics, astronomy, medicine, surgery, chemistry, mathematics, engineering, mechanics, and anatomy. There was also scientific activity in more humanitarian fields like sociology, linguistics and history: two examples are al-Biruni (1000) and Ibn Khaldun (1400 The Scientific Revolution must be seen to have its deep roots in Central Asian Islamic investigations into nature. The revolutionary aspect of Islamic science has at least three points: 1) its inclusivity: the Muslims brought together Chinese, Indian and Greek approaches, which by itself was unprecedented and fertile, as it led to comparison and criticism. 2) it introduced the quantitative approach, the inductive approach and the experimental approach: these three aspects are often considered the defining measure of modern science, and they are present in Islamic science. 3) it had an important institutional aspect: the rulers sponsored the building of astronomical observatories and the collaborative research of scholars; the oldest university is found in the Islamic world. In this sense, Islamic scientific activity was systematic, widespread and productive in a way the world had never seen. So with some exceptions there was scientific revolution in the Islamic world.
What evolutions did the institution of the Caliphate go through?
The first empire was the Umayyad empire, headed by Caliphs who belonged to Muhammad's tribe but not to his family, and who very quickly abandoned the simple Arab Muslim lifestyle of the early Muslims for luxury. The Abassids replaced the Umayyads in 750 after a revolution ousting them. Eventually, they set up their capital in a new city they called Baghdad. The city was to become the centre of the scientific and cultural revolution, aspects of which we described above. Initially, they based their legitimacy on Shiite doctrine (claiming descent from Ali). However, a thinker called al-Muqaffa (756) eventually worked out a political doctrine which put forward a new vision of who the Caliph was. It was neither Shiite, as after all it was difficult to keep on finding Alide heirs, nor Kharijite, whose purity and quarrelsomeness was difficult for an imperial outfit.
This evidently points to a further transformation in the meaning of the Caliphate: now it was really a religious rubber-stamping institution. Put differently, the Caliph had been reduced to a religious symbol, a symbol of the Muslim world's unity despite the plethora of different emirates and so forth. The Turks had a sultan: the world sultan is Arabic for power: in effect the religious Caliph was now granting power to entities over which he had little real control. The Seljuk Turks in Anatolia, and then the Ottomans, another Eurasian Turkic people who arrived after the Seljuks, were instrumental in finally defeating the lingering Byzantine empire in Anatolia. Their jihad against the Christian empire was conducted, initially at least, with the symbolic religious authority of the Caliph, but with little of his real military backing.
In 1254, the Mongols invaded Iraq, having already conquered Central Asia and Eurasia. Fearing the authority of the Caliph, they killed him: they did it by rolling him up in a carpet and beating him to death After this, the Caliphate disappears from Baghdad and in the post-Mongol period drops out of sight for a long time as an institution. Instead, the "protector of the two holy places" comes into its own as the real title of power in the Islamic world. And it is during this post-Mongol and post-caliphal time that Islam undergoes more enormous expansions into places like: West Africa (present day Chad, Nigeria, Mali); Indonesia and Malaysia (today the most populous Muslim nations in the world), Southern India, the Caucasus, and the Balkans. Mostly (except for the Balkans), Islam does not spread through armies Instead, especially in Malaysia and Indonesia it spreads through trade: merchants belonging to Sufi mystical orders set up prayer centers or mosques and bit by bit the religion spreads in local conditions, often absorbing and reshaping much local lore and law. New Muslims come to perceive Islamic authority through the lens of the pilgrimage to Mecca rather than through a single caliphate.