A report titled Global Trends 2025: A Tranformed World, issued last year by the US National Intelligence Council, advises us that a multipolar world-that is, a world characterized by multiple centers of power-is gradually emerging. The report attributes this to "the rise of emerging powers, a globalizing economy, an historic transfer of relative wealth and economic power from west to east, and the growing influence of non-state actors." Given these trends, it seems appropriate to ask whether a diffusion of power is indeed occurring, why we should care if it is, and what the implications may be for international politics.
The description of the present structure of world power as ...view middle of the document...
Each state can, if it has the power, despoil or conquer others. Thus each looks to its own capabilities relative to the others in order to defend itself.
Realists observe that the structure of world power has followed various patterns at various times and believe that these patterns naturally have consequences: Since security is the preemi- nent issue in an anarchic world, the distribution of capabilities to attack and defend should matter. Some base this belief on observation, others on deduction. Regardless, it is important to remember that structural realism is a theory of environmen- tal constraints and incentives. Structures con- strain. They push and they pull. The combination of global anarchy and the distribution of capabili- ties creates fields of force that affect all the states in the system but do not determine anything.
Different international structures do appear, however, to encourage different patterns of behav- ior. Modern international politics has mainly been a multipolar affair, featuring a handful of states with significant capabilities, all of them warily watching one another. During the cold war, we saw for the first time in modern history a bipolar structure of power, which lasted perhaps four decades.
The post-cold war world has seen an equally rare unipolar structure of power, which now
Barry r. Posen is a professor of political science and direc- tor of security studies at the Massachusetts Institute of Tech- nology.
Emerging Multipolarity: Why Should We Care?
Barry r. Posen
current History November 2009
"Isolation is perhaps the most dangerous situation in multipolarity, so states will pay close and constant attention to the game of coalition building."
348 • CURRENT HISTORY • November 2009
seems unlikely to last longer than the cold war's bipolar order lasted. Current discourse seems to expect that the structure of power will, if any- thing, revert quickly to bipolarity with the rise of China. It seems plausible, however, that a pro- longed period of multipolarity will occur before bipolarity reemerges, if indeed it ever does.
Measuring power Although political science strives for objective
measures of power, they are elusive. In interna- tional politics it is the powerful who measure relative power, and their assessments, though not fully auditable, are the ones that matter. This is not to say that statesmen spend their days specu- lating on the polarity of the international system they inhabit. Rather, they respond to the con- straints and possibilities they perceive. Over time their behaviors tell us which powers they believe matter, and why.
Two examples serve to demonstrate the dis- junction between seemingly objective measures of polarity and statesmen's behaviors. The Soviet Union was only barely in the league of the United States for most of the cold war in terms of economic capacity, yet we think of the era as a bipolar order. Likewise, the United States was far and...