Pundits often treat foreign policy decision making as a simple matter of morality or politics, and academics often ignore it entirely, viewing policy as driven not by individual officials but by broad structural forces. Foreign policy professionals, in contrast, generally see the subject as an arena of constrained choice. They try to figure out just how much freedom of action they actually have in a particular situation, and debate how best to use that freedom to advance the national interest. The hallmark of the serious professional's approach to foreign policy is not certainty but doubt; they live in a world with no easy answers, only an endless series of unpleasant tradeoffs. This collection is an introduction to that world. Originally published in Foreign Affairs, the essays gathered here offer a broad array of opinions on pressing topics ranging from handling rogue states to humanitarian intervention, from designing trade policy to dealing with the UN to managing relations with China.