When a civilization enters what he calls the time of troubles, s when civilizations advance or collapse by facing challenges. Toynbe didn't call it this, but i call it the goldilocks theory of history. If the challenge is to is not great enough, then civilization overcomes it too easily and it becomes lazy and complaisant. So we could say rome something like that maybecause it took a long time. Wasn't built in a day, and it didn't die in a day either. It took meo quite a long time for the roman empire to fall apart. But this is where goldyluck comes into play: if the challenge is just right,