The structuralist project, as we have seen in the preceding chapters, rests on maximum abstraction. The theoretical strategy is to make the fewest assumptions possible and use the smallest imaginable number of explanatory variables. Structural realists self-consciously sacrifice richness and depth for a simple, rigorous theory that holds widely across time and place.

In chapter 2, however, we saw that allegedly structural explanations typically rely on the interaction of structure and “unit level” (state) preferences. In chapter 3 we saw that anarchy alone has far fewer implications for state behavior than realists often suggest. This chapter extends this line of argument by examining the balance of power, which Waltz presents as a purely structural theory of international politics. I will argue that, once again, allegedly structural explanations either fail or prove not to be structural.

So far we have discussed the distribution of capabilities, the third element of structure, only in the context of the distinction between great powers, whose capabilities make them more or less equal players in international relations, and lesser powers, which appear in structural theories largely as objects acted upon by the powerful. Waltz, however, draws one of his principal substantive conclusions in Theory of International Politics on the basis of the distribution of capabilities: bipolar structures are more stable than multipolar structures. Waltz also addresses the balance of power more generally in his well-known argument that states in anarchy “balance” rather than “bandwagon.” These claims will occupy us in the first two sections of this chapter. The final two sections introduce a broader critique that emphasizes the difference between system and structure, opening the way for a discussion of international institutions (in chapter 5).