*Immoderate Greatness* explains how a civilization’s very magnitude conspires against it to cause downfall. Civilizations are hard-wired for self-destruction. They travel an arc from initial success to terminal decay and ultimate collapse due to intrinsic, inescapable biophysical limits combined with an inexorable trend toward moral decay and practical failure. Because our own civilization is global, its collapse will also be global, as well as uniquely devastating owing to the immensity of its population, complexity, and consumption.