He introduced the concept of “revealed preference” in a 1938 article. His goal was to be able to tell by observing a consumer’s choices whether he or she was better off after a change in prices, and indeed, Samuelson determined the circumstances under which one could tell. The consumer revealed by choices his or her preferences—hence the term “revealed preferences.” Samuelson is among the last generalists to be incredibly productive in a number of fields in economics. He has contributed fundamental insights in consumer theory and welfare economics, international trade, finance theory, capital theory, dynamics and general equilibrium, and macro-economics.