Abstract
Among systematic methods for forecasting the future of large-scale social systems, extrapolation from trend measurements is the most common. The search for a firmer conceptual basis of extrapolation has taken two forms. One is the notion that certain psychological elements held in common by the members of a social system presage subsequent sociocultural realities; these factors include images of the future, values, aspirations, and motives. The other approach is to project forward an understanding of the social system itself. In the discipline of sociology this attempt has been weightily theoretical, while in the nascent field of futures research it is atheoretical and prolific, resulting in such techniques as scenario writing, the Delphi method, simulation modelling, and cross-impact analysis. Although the overall number of procedures is large, so far just one has been substantiated satisfactorily.