International relations have been the object of widespread study and review in the United States since World War I. Attention has focussed alternately on the flow of events, the goals and standards, and the underlying principles of world affairs. Primary emphasis has been directed to empirical, normative and theoretical problems. Along the way, scholars, statesmen and observers have singled out certain factors from the myriad dimensions of international society. Students have looked for concepts and methodologies by which order and meaning could be derived in this as in other complex fields.