The “theory toolbox” adapts simple, lab-tested theories into a framework that can explain complex historical and contemporary events without resorting to data mining, induction or generalization. To demonstrate its use, we apply it to explain the development of political states, the nuances of European feudalism and the dynamic interdependence along the Han-nomad frontier. The theory toolbox is flexible. Like legos, models in the toolbox can be combined in various ways. Consequently, it can be applied to a wide array of social situations. As social theory advances, new models are added, and existing ones are refined or replaced; the theory toolbox improves its scope and precision of application. Thereby, cumulation creates a greater scientific understanding of the world.