esults achieved seldom correspond to the intentions of actors (52).
Waltz argues, then, that only systems theory can give the analyst of international relations a clear picture of why events happen the way they do on a global level. The point is that there are many forces at work in international relations which are beyond the influence of individual states. The world is more than the sum of all the individual nations.
The question might be asked, then, whether international relations are unpredictable themselves. A study of the history of international relations makes clear, however, that there are many similarities among different eras in global politics. Despite the fact that nations and leaders are constantly changing in the world,
continuities are as impressive, or more so. . . . The texture of international politics remains highly constant, patterns recur, and events repeat themselves endlessly. The relations that prevail internationally seldom shift rapidly in type or in quality. They are marked instead by dismaying persistence (53).
To Waltz, then, changes which do occur in the field on international relations cannot be explained or analyzed effectively by using reductionist theories. Only systems theories consider the "big picture" of international relations: "The repeated failure of attempts to explain international outcomes analytically---that is, through examination of interacting units---strongly signals the need for a systems approach" (55).
The remainder of the chapter examines systems theory and explains why it is an effective approach to international relations. Waltz says it is clear that reductionist theory does not work because
propositions at the unit level do not account for the phenomena observed at the systems level. Since the variety of actors and the variations in their actions are not matched by the variety of outcomes, we know that systemic causes are in play. Knowing that, we know furth...