This book is about the science and politics of human needs. Since the French Revolution, human needs have served to legitimize or to challenge modern forms of social organization. The precept that every human being deserves a minimal standard of living is a key premise of human rights, state welfare and international development aid. But needs also serve to reinforce social difference. The so-called “nature” of sex or race, one group’s inferior needs, justified lower wages and nutritional standards for women and colonial populations. Economies of need appeared to govern biological and social processes. Anatomists believed that an animal’s physical structure could be derived from its basic needs. Ethnographers measured a people’s level of civilization along a scale of ‘primitive’ and ‘advanced’ human needs. Continental political economists placed human needs at the center of their analyses. Needs mobilized technologies of measurement - scale balances, chemical weights, calorimeters, social surveys, statistics - and technologies of welfare – minimum wages, family allowances, rationing and poor aid. This book interrogates the meaning and function of ‘life’ in living wage, the ‘vital’ in vital minimum. The book argues that a science of human needs undergirded the modern wage economy and the welfare state.