This book deals with factors affecting economic growth in knowledge-based societies. It is shown that the interaction between material and nonmaterial values is the ultimate source of all economic growth including business cycles. The model developed predicts the quantitative facts concerning the business cycles better than the conventional real-cycle models. It also produces, besides the balanced-growth path, another growth path whose existence is verified by empirical facts. The results give strong evidence of the economic relevance of nonmaterial values. They also prompt a new vision of the stochastic elements in the business cycles. Nonmaterial values are analysed, and their interaction with economic growth is also illustrated in terms of an entropy formalism of historical analysis.