It says something important-and healthy- about America’s changing idea of itself that in recent years discontent with our foreign policy has taken the opposite course. The more one criticized current policy, the more likely one opposite was to believe that past policy had been good. Both of these responses- looking for the “good America” or the bad- have been right about the importance of the past, but neither has gotten us much closer to the truth. We won’t fully understand today’s choices unless we explore the ideas and impulses that over many decades defined America’s way in the world- where they came from and why they lasted, what they have done for us (and to us), which ones are ready for the scrap heap, and which can be put to work again.