American power in the world relies on these ideals of openness and critical debate.

Leadership experts and the public alike extol the virtues of transformational leaders - those who set out bold objectives and take risks to change the world. We tend to downplay 'transactional' leaders, whose goals are more modest, as mere managers.

We live in a world of diverse cultures, and we know very little about social engineering and how to 'build nations.' And when we cannot be sure how to improve the world, hubristic visions pose a grave danger.

America rests on shared values rather than shared ethnicity.