As historians of Southeast Asia turn to the study of rural history, they will have to resort increasingly to theoretical aids as an answer to the paucity of written records. Such theory, drawn from the other social sciences, must be shaped and tested to fit the needs of the historical discipline. For example, the work of Ester Boserup and Clifford Geertz on the relationship among population density, land usage, and socioeconomic behavior has applicability to problems of the evolution of Southeast Asian rural society under colonial impact. A comparison of Geertz' study of agricultural involution in nineteenth century Java with my own work on Pampanga Province, Philippines, provides some first steps towards a theory of rural change. Specifically, a modern cash crop economy produces more sophisticated contractual relations between tenants and landowners regardless of changes in population density per agricultural hectare. And, in the face of a scarcity of resources (e.g., land, cash, machinery, etc.) needed for modern agriculture, a given society will evolve highly complex institutions in order to share as far as possible those commodities in short supply. Specific types of institutions may develop to meet given needs, and the greater the number of shortages, the more involuted the society will become.