I don't think it's difficult for any of us to understand why the US China relationship is so important. The two countries are the world's largest economies. They are the largest contributors to global carbon emissions. They have the world's largest military establishments, they are both permanent members of the United Nations security council, they matter. And therefore the relationship between them matters as well. But what kind of relationship? Is this important relationship going to be. A second reason why managing it is so important, is that the relations between the two countries are both complex and uncertain. Consider the range of forecasts presented by some of the most thoughtful observers in the two countries' foreign policy establishments. Some foresee a coming strategic rivalry between them. What some call a new cold war because of the differences and the growing level of mistrust between the two countries. Others express concern that territorial disputes between China and American friends and allies in the Western Pacific could even give rise to a military confrontation, into which the United States might be drawn. Others, much more optimistic, foresee the inevitability of a cooperative relationship between China and the United States, arguing that the severity of global problems in the contemporary world. Terrorism, climate change, pandemic diseases, humanitarian disasters, financial crises and the like will demand solutions. And will therefore compel Beijing and Washington to cooperate in providing those solutions. Some have gone even further, forecasting that China and the US will in a way replace the G7 or G8. And form a G2, a consortium of the world's two largest economies, who will increasingly work together to manage the international economy and protect the global commons. Now as different as these two sets of forecasts are, one far more pessimistic, the other far more optimistic. They are relatively simple and straightforward, predicting either an essentially cooperative relationship or an essentially antagonistic one. But other analysts, myself included, argue that China and the U.S.have such a complex set of common and divergent interests and perspectives that their relationship will be equally complicated. China and the U.S. have common concerns about some regional and global issues, but their two societies are organized around different values and different institutions. Despite China's rapid growth and growing prosperity, the two countries are at very different stages of development. They apply different norms to international issues. Their publics are highly nationalistic. Their political elites do not have a high degree of mutual trust. So, analysts who take this more complex approach to the US China relationship, therefore predict that it will be a mixture, a blend of competition, co-operation and potential conflict. They then debate what the balance among those elements will be. Which aspect will be more important, and which will be secondary. Although that approach is superior to an analysis that attempts to forecast a simpler relationship between the two countries, whether positive or negative. There still is an important element missing in the analysis that I want to emphasize today. The key question is not just what blend of the positive and the negative will characterize US, China relations? But what kind of co-operation? What kind of competition? And if it comes to it, what kind of conflict the relationship will reflect? If the different possibilities within each of these three types of relationships. Some of which will be more beneficial and some will be more costly than others that I want to explore in the remainder of my remarks.