Fishing for any sort of "turning points" or "decisive moments" in History is almost always an exercise in pushing some purposeful narrative. I think the only wa

Fishing for any sort of "turning points" or "decisive moments" in History is almost always an exercise in pushing some purposeful narrative. I think the only way to get a sense for Historical understanding is to read multiple narratives and understand that there are multiple points of view and complex systems change are complex and made of a whole lot of small changes, which cannot be all captured or captured fully by any one narrative. Some periods transitions may be construed as "phase transitions" by scholars advancing interdisciplinary and "complex systems" types of analytical frame. Still, we shouldn't conflate such explanations with very well defined constructs from physics which rely on highly complicated mathematical models. We don't have nearly enough data to build such models for human behavior or social systems. It is just a metaphor. Between the height of Rome's Imperial power in the second century to the dawn of Medieval Europe in the fifth you'd need thousands of pages to reasonably cover all the aspects of what changed and how. Simply put, there is a whole lot of irreducible complexity in History.