Writing in the Ottawa Citizen, Robert Sibley comments on that epoch and explains what stopped it dead in its tracks lo those many, many centuries ago:
Blame the imams. In the 11th century, Imam Abu Hamid al-Ghazali, a brilliant if tormented theologian, published The Incoherence of the Philosophers, effectively bringing to conclusion centuries of debate in the Muslim world about the primacy of reason versus that of revelation. Reason makes us question things, makes us doubtful and uncertain, al-Ghazali argued. He attacked philosophers who thought that humans could know the world by means of rational thought. Reason, he said, leads to despair. Only divine revelation, the word of God as revealed in the Koran, provides certain knowledge of how best to live. Human reason must submit to Allah's will.Sounds about right to me.
A century later, another Muslim philosopher challenged al-Ghazali's views. In The Incoherence of the Incoherence, Ibn Rushd -- better known in the West as Averroes -- argued that reason was God's gift to mankind and was to be used for the betterment of society. Ignorant theologians should not intrude on areas they don't understand. It was too late. The imams carried the day. Averroes' books were burned and he fled into exile. The voice of reason fell silent in courts of the caliphs and Muslim culture gradually ossified.
Some scholars argue that Islamist terrorism can be traced to this eclipse of reason...