This article recounts the intellectual history of the UNDP’s Human Development Index. It begins with the early history of welfare economics and follows this field through three successive revolutions in thought culminating in the theory of human development. The first section traces this history from the origins of economic “utility” theory to Sen’s human capabilities approach. The second section is a chronicle of past and present measures of social welfare used in the fields of economics and development, including national income and a variety of composite measures up to and including HDI.