Clearly the United States does lead the world in some major ways. It operates the largest single national economy and does so on relatively open terms that serve to engage other national economies as well. It provides a primary impulse for technical development in a variety of areas, some of which are transforming the basic circumstances of all human activity. It possesses a uniquely capable military establishment, the only one with full global reach and the only one able to perform the most advanced military missions. It maintains a highly diverse society that to some degree incorporates most of the world's cultural traditions and stimulates many of the world's popular aspirations. For these reasons the United States commands attention, inspires emulation, and incites reaction – all features of what is generally meant by the idea of leading.

But just as clearly the issue of world leadership goes beyond the obvious fact that the United States is inherently consequential. Leadership worthy of the name involves appropriate, explicitly formulated and successfully implemented intention. To lead the world under current circumstances, the United States would have to initiate a deliberate redesign of the international political order and would have to undertake the major innovations in policy and in institutionalised arrangements necessary to bring it about. The qualities necessary for such an exercise are not automatically conferred by size, prominence or even historical achievement. It is not yet evident whether the United States will be able to rise to the occasion.