Waltz begins this influential essay with an extended discussion about systems theory. He defines a system as "structured," that is, it has a
system-wide component that makes it possible to think of the system as a whole.
Within the system of international politics, he argues (as a realist) that ideologies, personal characteristics of world leaders, and other factors are largely irrelevant. Unlike domestic political systems, there is no formal hierarchy, and so the system of world politics is fundamentally "decentralized and anarchic." There are no well-defined roles for nations, and no nations are bound to obey; no nations are entitled by their position within the system to lead other nations. To explain how the system of world relations works, Waltz turns to what he describes as a classical economics model, the one pioneered by Adam Smith. In this way of thinking, a system exists even though everyone within it is an independent (economic) actor. People behave in predictable ways—to maximize their profits. In the system Waltz describes, states function in an analogous way: they seek to "ensure their survival." This is a
prerequisite to achieving any [other] goals that states may have,
such as regional domination, global conquest, and so on. Waltz acknowledges that not all sovereign states are equal—there is obviously a hierarchy between them—but he observes that this hierarchy is not related to goals or intents, but to capability. Some states, in short, are much stronger than others, and this is the most important factor in understanding international relations, according to Waltz.
Ultimately, because all states are out to preserve their own existence, what matters in international relations is power. "Among states," Waltz writes, "the state of nature is war." He describes international relations as a "self-help system," one in which the various units, or states, interact with the most selfish of motives—their own preservation. This creates a major problem, which is that states do not act in the interest of the world unless they believe it is also in their own interest. They also engage in behavior that they know is dangerous—Waltz cites the British-German naval buildup ahead of World War I—if it suits their main interest, which is survival. In this system, Waltz concludes, it is meaningless to expect nations to do anything with the interests of the world in mind. In fact, world organizations that restrain the powers of nations are self-defeating according to this line of thinking. Power matters in international relations, and it is actually the threat that the actions of one nation might lead to war, which could in turn lead to their destruction, that provides the best insurance against bloody conflicts. This is why, Waltz argues, we must accept that the global system is "anarchic" in the sense that it lacks any predisposition toward transnational organization.