Pop quiz: Can you match the following quotes to the president who said them?*

1) "Our best days lie ahead."
2) "America's best days … lie ahead."
3) "America's best days are still ahead."
4) "America's brightest days are still ahead."
5) "Our best days are still ahead of us."

a) Nixon (1971)
b) Reagan (1982)
c) Clinton (1996)
d) Bush (2007)
e) Obama (2011)

For years, politicians have tried to reassure us about the future -- because, for years, we have been secretly worried that America is in decline. Robert Kagan doesn't believe we are in a "post-American world," but he worries that many of us are far more complacent about this than we should be. Kagan served in the Reagan State Department, and is now a Senior Fellow at the Brookings Institute, so he knows his way around Washington. His new book, The World America Made, challenges us to consider what it means for America to be a superpower, and what decline would really look like.

Kagan observes that many people see the rise of democracy, free markets, and free trade as historically inevitable. In this view, if America were to follow a more isolationist path, the rest of the world would step up and share the burden. He writes, "The irony is that the success of the American world order has made it possible for so many people to believe … that American power may no longer be necessary to sustain it … It is as if New Yorkers strolling through a safe Central Park decided that police were no longer going to be needed."

Unfortunately, history disagrees. Kagan methodically shows us that fascism, communism, and military dictatorships have regularly gone in and out of fashion, and that our absence could easily spur other, less desirable models to proliferate. He also notes that historical examples of a multipolar world, such as that seen with the "great powers" of the nineteenth century, included gruesome wars on a regular basis.

The World America Made claims that the world is better off for America's dominance. Certainly, we have benefited. But Kagan enumerates the benefits for everyone else -- dramatic improvements in global standards of living, relative peace for decades -- and it is difficult to understate the effects, whether because of us or despite us.

Kagan refrains from making specific policy recommendations, and he stays clear of many partisan battles that might label this as a book for Democrats or Republicans. But he is clearly urging us to stay engaged and to resist the temptation to focus on "nation building at home." This is a thoughtful book and an interesting counterpoint to the political rhetoric of an election year. It's a safe bet that serious policy types will be listening.

*Answers: 1-a, 2-b, 3-c, 4-d, 5-e