This volume offers a synthesis of what is known about very large and very small common-pool resources. Individuals using commons at the global or local level may find themselves in a similar situation. At an international level, states cannot appeal to authoritative hierarchies to enforce agreements they make to cooperate with one another. In some small-scale settings, participants may be just as helpless in calling on distant public officials to monitor and enforce their agreements. Scholars have independently discovered self-organizing regimes which rely on implicit or explicit principles, norms, rules and procedures rather than the command and control of a central authority. The contributors discuss the possibilities and