Question of balance.

Professor Wohlforth's article, ("Unipolar Stabilty: The Rules of Power Analysis," Spring 2007), is a thoughtful attempt to counter the suggestion that the "unipolar moment" identified by Charles Krauthammer has come to an end. This is an important point, particularly given the focus on polarity and balance of power associated with realism. It has triggered a long post-Cold War debate regarding the likelihood of balance re-emerging within the international system. Kenneth Waltz, in Theory of International Politics, insisted that the formation of balances of power is something of an iron law of international relations, perhaps the only one. A straightforward reading of realism therefore suggests that the present unipolar moment is an aberration and must, sooner or later, give way to a renewal of balance of power politics.

However, the historical record does not support this assertion. Unipolarity has been a frequent occurrence throughout history, and periods without balances of power are as common as balanced systems. When such balance of power systems have existed, they have frequently been followed by long periods of hegemony. Based on the historical record, there is every reason to believe that the period of American dominance may be a very long one. Where expansion of the system is difficult or impossible, hegemonies tend eventually to occur. In this regard the current global system is clearly a closed one, where expansion is not possible in the short or medium term.

Wohlforth is right to argue that American unipolarity is much more likely to endure than critics suggest. He is also correct in urging caution in terms of the assumptions and methodologies used to support the argument for emerging multipolarity. Thus the suggestion that China has already emerged is justly criticized by pointing both to the real weaknesses of China and the methodological problems associated with using purchasing power parity (PPP) as a measure of comparative economic muscle.

Nonetheless, Wohlforth's essay raises as many questions as it answers. Questioning the utility of using a primary indicator such as PPP as an economic measure raises the broader question of why "multipolarity" should be understood purely in adversarial military terms in the contemporary international system. While defining "power" admittedly is like trying to nail jello to the wall, power can take many forms, and rivals and balancers may cross single categories. The current system is reasonably characterized as a globalized one, yet it is also profoundly regionalized. Certain states, such as China, have a capacity to compete at the regional level that they lack at the global one. Similarly in certain areas, allies and partners of the United States are rivals with considerable blocking power: the European Union in international trade, and Russia in energy politics are just a few examples. States operating in multi-dimensional security complexes have a capacity to balance power in a variety of ways, and even when capability in one category is overwhelming, it may not directly translate into an ability to consistently determine outcomes, as the American difficulties in Iraq demonstrate.

The existence of varying types and levels of power complicates the question of determining the form of polarity in the contemporary international system. In certain dimensions, such as the economic dimension, multipolarity may be identified, and made complex by the cross-cutting alliances and interest cleavages of the actors. When power is defined in a more limited military sense however, this is not the case, as Wohlforth correctly points out. Power distribution and polarity are both important, but they are not the same thing. Confusing the two obscures the real trajectory of America's comparative power and influence in the contemporary system.

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MICHAEL SHEEHAN is Professor of International Relations, and director of the Callaghan Centre for the Study of Conflict at Swansea University