Until the end of World War II mathematical economics was almost synonymous with the application of differential calculus to economics. It waj on the strength of this technique that the mathematical approach to economics was initiated by Cournot (1838) and that the theory of general economic equilibrium was created by Walras (1874) and Pareto (1909). Hicks's Value and Capital (1939) and Samuelson's Foundations of Economic Analysis (1947) represent the culmination of this classical era.