This document provides an overview of the evolution of political economy from the pre-classical era to modern times. It discusses early schools of thought like mercantilism and physiocracy. It then covers Adam Smith and the classical economists of the 18th century. Rival schools emerged like neo-mercantilism, institutionalism, and Marxism. The document also discusses Keynesian political economy in the 20th century and monetarist criticisms of Keynesianism. The intellectual history of political economy has included many influential thinkers and ongoing debates around the appropriate roles of government and markets.