What is sustainable development?

This paper introduces two axioms that capture the idea of sustainable development and characterizes the welfare criterion that they imply. The axioms require that neither the present nor the future should play a dictatorial role in society's choices over rime. Theorems I and 2 show there exist sustainable preferences which satisfy these axioms and provide a full characterization. Theorems 3-5 study a standard dynamical system representing the growth of a renewable-resource economy, give a "turnpike" theorem, and exhibit the differences between sustainable optima and the ones according to discounted utilitarianism.