Like a lot of people, I am no big fan of what electoral politics has become in America. One reason is the appalling rhetoric. As this political season heats up, one can reasonably expect the Democrats, as members of the party out of power, to talk about everything that has gone wrong in the country under its current leadership, just as in the 2000 election cycle, the Republicans devoted themselves to the same exhausting nonsense.

The announcement that the sky is falling is nothing new in our political life, of course, and it plays extraordinarily well, even among voters in a land that has almost everything. America has the world's mightiest economy, foremost scientists, best health care, and most astonishing selection of consumer goods. The air and water are growing cleaner and cleaner. The streets are growing safer and safer. Diseases that ravage other parts of the world are mostly either unknown or under control here. Our range of constitutional freedoms, even in a time of tension over terrorism, remains far broader than anywhere on the face of the globe.

Yet when a politician, or an activist, or a television commentator tells us that the land is actually a mess, that things are getting worse, we perk up and listen, for a distinct public pessimism is the mark of our era. Good news we greet with skepticism. Bad news we believe at once.

The question of why we behave this way—and what America might be like if we should stop—motivates a marvelous recent book by Gregg Easterbrook, titled The Progress Paradox: How Life Gets Better While People Feel Worse. "If the Western world has known a Golden Age," he writes, "it is right here, right now."

Why, then, are people unhappy? Why do we so engage in what Easterbrook calls "the collective ...