Mr. Obama faces accusations that he is organising a retreat from American greatness. But he has a perfectly coherent response to this charge. The foundation of American strength in the world is the power of its domestic economy. Unless he puts “nation-building at home” first, US global leadership will be based on rotten foundations. Besides, Americans are sick of foreign wars and want the president to improve their lives at home. The problem with Mr Obama’s ambition to concentrate on economic and social reform is not that it is ignoble, but that it may be unrealistic. It would be highly convenient if the world would calm down for a while. Yet international crises are inevitable – and even a cautious, non-interventionist, administration can be dragged in.