In contrast to the Mutazilite school of Greek-inspired philosophers, the Asharite view was that comprehension of unique nature and characteristics of God were beyond human capability. And that, while man had free will, he had no power to create anything. It was an ignorance-based view which did not assume that human reason could discern morality.
Despite being named for Ashari, the foundation of the school's thought was "The Incoherence of the Philosophers", by the polymath Al-Ghazali (d. 1111). He laid the groundwork to "shut the door of ijtihad" centuries later in the Ottoman Empire. This is one of the most influential works ever produced. Ibn Rushd, a Mutazilite, famously responded that "to say that philosophers are incoherent is itself to make an incoherent statement." But this shallow response could not refute Al-Ghazili's view, which was very broadly based, and eventually came to dominate:
His The Revival of the Religious Sciences in Islam was the cornerstone of the school's thinking, and combined theology, skepticism, mysticism, Islam and other conceptions, discussed in depth in the article on Islamic philosophy.
His mode of thought was the standard in the Ottoman Empire. When Ataturk sought to separate Turkey from dominance of religious thought in 1922 he changed the script used in the Turkic language from Arab calligraphy to the Latin script, and forbade translations of some works, including Al-Ghazali's. Such was the power of his thinking over eight centuries later. Even today, with a moderate Islamic party in power in Turkey, challenging some of Ataturk's doctrine, taking positions on international affairs based on foundations of thought laid by Al-Ghazili, he influences.
Two other philosophers influential in the rise of the Asharite school were:
A critical spirit of inquiry was far from absent in the Asharite school. Rather, what they lacked, was a trust in reason itself, separate from a moral code, to decide what experiments or what knowledge to pursue. The modern sociology of knowledge could reasonably be said to be based firmly on Asharite views, as illustrated by modern experiences of science without ethics.
The influence of the Asharites is still hotly debate today.
Most agree that the Asharites put an end to philosophy as such in the Muslim world, but permitted these methods to continue to be applied to science and technology. The 12th-to-14th century marked the peak of innovation in Muslim civilization. During this period many remarkable achievements of engineering and social organization were made, and the ulema began to generate a fiqh based on taqlid ("blind imitation") rather than on the old ijtihad. Eventually, however, modern historians think that lack of improvements in basic processes and confusion with theology and law degraded methods:
Ironically, the rigorous means by which the Asharites had reached their conclusions were largely forgotten by Muslims before The Renaissance, due in large part to the success of their effort to subordinate inquiry to a prior ethics - and assume ignorance was the norm for humankind.
Modern commentators blame or laud Asharites for curtailed much of the Arab world's innovation in sciences and technology, then (12th century to 14th century) leading the world. This innovation was not in general revived in the West until The Renaissance, and emergence of scientific method - which ironically was based on traditional Islamic methods of ijtihad (open inquiry) and isnah (backing or scientific citation). The Asharites did not reject these, amongst the ulema or learned, but they stifled these in the mosque and discouraged their application by the lay public.
It was a drastic shift in historical initiative, foreshadowing later loss of Muslim Spain and the discovery of the Western Hemisphere - both in 1492. But the decisive influence was most likely that of the new Ottoman Empire, which found the Asharite views politically useful, and were to a degree taking the advantages of Islamic technologies, sciences, and openness for granted. Which, for some centuries after as the Ottomans pushed forth into Europe, they were able to do - losing those advantages gradually up until The Enlightenment when European innovation simply overwhelmed that of the Muslims.
The Asharites may have succeeded in laying the groundwork for a stable empire, and for subordinating philosophy as a process to fixed notions of ethics derived directly from Islam - perhaps this even improved the quality of life of average citizens. But it seems the historical impact was to yield the initiative of Western civilization to Christians in Europe.