> Only complexity, Tainter argues, provides an explanation that applies in every instance of collapse. We go about our lives, addressing problems as they arise. Complexity builds and builds, usually incrementally, without anyone noticing how brittle it has all become. Then some little push arrives, and the society begins to fracture. The result is a “rapid, significant loss of an established level of sociopolitical complexity.” In human terms, that means central governments disintegrating and empires fracturing into “small, petty states,” often in conflict with one another. Trade routes seize up, and cities are abandoned. Literacy falls off, technological knowledge is lost and populations decline sharply. “The world,” Tainter writes, “perceptibly shrinks, and over the horizon lies the unknown.”