How can we make collective decisions fairly? What does it mean to properly balance conflicting interests? How can we combine the well-being of individuals into a concept of societal well-being? We explore these and related ethical questions from the perspective of economic theory. A central tool is the axiomatic approach, which calls for decisions to be consistent, in precise senses, across related situations. Possible topics include: rationing problems, the Shapley value, fair division, discrimination, voting theory, foundations of utilitarianism and egalitarianism, measurement of inequality, population ethics, intergenerational equity, and concepts of equal opportunity.