If we fall, we’ll get back up again. If we tear it down, we’ll rebuild, bigger and better. That’s what we tell ourselves. That’s what we believe. That isn’t necessarily what happens, as the ruined cities and collapsed civilizations scattered around the world demonstrate. Where does this belief come from? And how does it affect societies, both in the real world and in science fiction? Background: The Generational Cycle Theory The “Fourth Turning” theory suggests that societies go in cycles, typically over four generations.