That's hard to answer. The philosophical, mathematical, and scientific flourishing in the the silk road cities of central Asia in particular during the Islamic

That's hard to answer. The philosophical, mathematical, and scientific flourishing in the the silk road cities of central Asia in particular during the Islamic golden age seems to have ended in the 1000s. Some people blame the influential book The Incoherence of the Philosophers[1], maybe they're right or maybe it just captured the zeitgeist and was effect rather than cause. Before too long the Mongols came. Plan A for China was originally to kill everyone, burn the fields, and raise the biggest herds ever on the resulting grassland. Thankfully this was quickly abandoned for Plan B, conquer and tax the people. But Plan B needed larger armies than Plan A and when Khwarezmia offered an unforgivable insult while the bulk of the Mongol army was needed pacifying China they got the Plan A treatment and why it seems so weird to us that a contender for largest city in the world could have ever been in Turkmenistan. [1]https://en.wikipedia.org/wiki/The_Incoherence_of_the_Philosophers https://en.wikipedia.org/wiki/The_Incoherence_of_the_Philoso...