(To Yukari Ryle whose son's HS teacher praised Neil Ferguson)
The High School Teacher is wrong, the "Imperial Overstretch" theory is like Global Warming, an interesting narrative that lacks causality. It also fails to explain any benefit from restraint in the face of rising threats. It also fails to consider the role of culture in enabling a society to be efficient at administration and restrained in resource allocation. The profligacy of unproductive Ottomans does not mean that productive democracies are self destructive. This is the kind of topic that the Belmont Club used to cover better than anyone else.
Perhaps there is a link between various theories propounded by the Left to justify a sense of despair leading to a sense of fatalism and surrender to a managed decline under aristocratic control. Consider Imperial Overstretch, or Anthropogenic Global Warming, or Keynesian Monetary Theory, or Classic Marxism. In each case, despite the appendage of a vast and complex apparatus and claims of scientific rigor, they are ultimately dependent on arbitrarily defined categories and the uncritical acceptance of undefined terms or the expectation of results that are not predictable with the tools available. In each case they depend upon a faith in a self selecting elite with access to secret knowledge to make decisions for the greater good. Each is a form of Gnosticism. The outcomes all resemble the Oligarchic Socialism of Nineteen Eighty-Four.
The appeal of Islam may partly rest on its' granting a similar exalted role to the qadis or scholars of the sacred texts. Despite temptations and lapses the expounders of esoteric doctrine in Judaism and Christianity have tended to lose influence over time. The reasons for this disparity need more investigation.