Why is it that some economies grow faster and/or are richer than others? What are the ultimate sources of persistent growth in average per capita incomes? Are market forces sufficient to ensure macroeconomic stability and full employment over time, despite technical progress and population growth? The “Solow model” illustrated in this chapter is the traditional tool economists have been using over the last six decades to answer these fundamental questions. The model constitutes an analytical description of the pure “mechanics” of the process of economic growth in a capitalistic system. It studies neither the sociological premises lying in the back of these mechanics nor the modalities of functioning of precapitalistic economies. In this respect, it cannot be considered a model of “economic development”. Yet, the Solow model is in a sense the best stylized description of how an already advanced, fully capitalistic economy should work and grow. It provides a very clear point of reference to conceptualize and understand the differences between the real world and its theoretical idealization. “Technical progress is not fast enough”, “the bourgeoisie is oriented towards luxury consumption instead of being committed to growth and development”, etc.: these political judgments and somehow vague statements become much clearer and useful thanks to the insights of the Solow model.