This lecture, delivered by Ted Bergstrom to undergraduate and master's students at the Australian National University and the University of Canterbury, introduces the concept of a primitive public economy through the example of Anne and Bruce, who share a room and have preferences over temperature and cribbage. The lecture uses indifference curves and the concept of Pareto optimality to analyze how they can reach an agreement on their shared living conditions. It then generalizes this analysis to more people and commodities using the calculus of functions of several variables, specifically the method of Lagrange multipliers. The lecture also discusses the utility possibility frontier and the conditions for efficient resource allocation, including the Samuelson condition for public goods. It concludes with a discussion on social welfare functions and the role of economists in providing advice without a definitive social welfare function. The lecture also touches on pollution and congestion issues, and introduces the Groves-Ledyard mechanism as a demand-revealing mechanism for public goods.This lecture, delivered by Ted Bergstrom to undergraduate and master's students at the Australian National University and the University of Canterbury, introduces the concept of a primitive public economy through the example of Anne and Bruce, who share a room and have preferences over temperature and cribbage. The lecture uses indifference curves and the concept of Pareto optimality to analyze how they can reach an agreement on their shared living conditions. It then generalizes this analysis to more people and commodities using the calculus of functions of several variables, specifically the method of Lagrange multipliers. The lecture also discusses the utility possibility frontier and the conditions for efficient resource allocation, including the Samuelson condition for public goods. It concludes with a discussion on social welfare functions and the role of economists in providing advice without a definitive social welfare function. The lecture also touches on pollution and congestion issues, and introduces the Groves-Ledyard mechanism as a demand-revealing mechanism for public goods.