Pinpointing the causes of Central Asia’s golden age is all the more difficult because the great minds who gave the age its brilliance were such a diverse lot. A few came from wealthy landed families and could live off their estates, while others, such as Ibn Sina and al-Biruni, won appointments to lucrative high offices. But they were exceptions. Most of the thinkers were full-time scientists, scholars, and intellectuals, or at least aspired to be. With no universities or academies of science to support them, this was no easy undertaking. Even if they assembled a few paying students, the resulting income never provided enough to sustain them. And so, by default, they relied on the patronage of rulers.
Here was one of Central Asia’s great strengths. To be sure, a would-be scientist could strike out for Baghdad in hopes of joining the House of Wisdom, an academy of sciences established by the Central Asia–born caliph al-Ma’mun. But there were many local rulers and courts throughout the region, just as there were also in Persia to the west. All gave a respectful nod to Baghdad but considered themselves functionally independent. Each of these rulers was a kind of caliph in his own right, ruling in a thoroughly authoritarian manner and defending his territory with a large army of Turks. But they also promoted trade, collected taxes, built splendid capitals, and, significantly, spent fortunes on the arts and sciences. One such court was at Gurganj, where al-Biruni worked. Another was at the already-ancient walled city of Samarqand, where between 850 and 1000 the Samanid dynasty maintained a magnificent library, intense salons where savants discussed the Great Questions, and a lively social world centered on music and poetry.
…[A]t least four factors contributed to the region’s decline. First, and perhaps foremost, nothing endures forever…In the case of Central Asia, even more than with the Arabs to the West, the mighty stimulus for original thinking had been the challenge of mastering and assimilating vast and unfamiliar bodies of thought, from ancient Greece, the Middle East, and India. By 1100 this had been accomplished, and no comparably huge body of new learning presented itself thereafter…Second, religions, like the cultures of which they are a part, go through cycles, beginning in dynamism, self-confidence, and experimentation and then hardening into orthodoxy…a third and much more specific factor was at work: the Sunni-Shia split within the Muslim faith…the reigning Sunni rulers across the region tightened their grip on all who might be suspected of schismatic leanings…The transformative figure, Abu Hamid Muhammad ibn Muhammad al-Ghazali (1058–1111), a philosopher and theologian, launched a frontal attack on the dangers posed by the unrestrained exercise of reason. The title of his most famous work tells it all: The Incoherence of the Philosophers (i.e., scientists). Like the Grand Inquisitor in Feodor Dostoyevsky’s The Brothers Karamazov, al-Ghazali intimately knew his enemy, in this case Aristotelian empiricism, which had attracted the best minds of the region. Attacking Aristotle, he attacked all contemporary rationalists, and to devastating effect.