“To maintain international peace and security …” is the first purpose listed in Article I of the United Nations Charter, and it is generally conceded to be the Organization's most important one. Although the United Nations Charter provides procedures for both peaceful settlement and peacekeeping, the peacekeeping role has been more active and more contentious. Indeed, without an authoritative organ for interpreting the Charter each Member has been left to determine for itself the meaning of such fluid phrases as “enforcement action,” “national sovereignty,” and “primary responsibility,” to mention only a few. The result has been a divergence of views which surprises all but that consummate logician—the reasonable man.