“The Soviet Union is now engaged in an audacious attempt JL to upset the established balance of power prevailing in Europe.” This statement was used by C. L. Sulzberger, writing in the New York Times for March 23, 1952, to open a discussion of the Soviet offer to establish a unified and neutral Germany. It symbolizes the startling renaissance of the balance of power concept in recent years not only in the pages of learned journals, but in the daily press and in radio as well. This rebirth is probably attributable to the effort to reconsider the notions concerning international relations generally held during the League of Nations period, notions which emphasized open diplomacy, collective security, and the use of arbitration instead of unilateral force. The apparent futility of these methods seemed to call for the reintroduction of more meaningful concepts into the analysis of international affairs, and the balance of power thus reappeared as part of the general trend to re-establish the primacy of power as the key to the understanding of interstate relations. There would be no difficulty in this development if the term “balance of power” were free from philological, semantic, and theoretical confusion. Unfortunately, it is not. The term is defined differently by different writers; it is used in varying senses, even if not defined exactly at all; and, finally, it is the focal concept in several quite distinct theories of international relations. The purpose of this article is the clarification, not only of the verbal differences in meaning, but also of the applied meanings of the “balance of power” phrase as they vary in accordance with the intentions of the users. The necessity for such an attempt may be demonstrated by an introductory discussion of the variety of thought on this topic, in terms of substantive meanings no less than in terms of systems of classification.