HISTORY IS a lot like forestry. In the latter, you often can’t see the forest for the trees, and in the former you often can’t see the epoch for the incidents. Though it hardly seems as momentous as the Great Depression or the civil rights era, our current period may be one of the most significant in American history — one that may well determine what kind of country we will be for decades hence. To put our own times in focus, it helps to ask: What will historians 50 or 150 years from now think of the early 21st century?

It is an apt question, because history has a way of challenging and altering the perceptions that any time has of itself. In its own day, for example, the 1920s were a boon period that gave rise to national free-spiritedness. In the long eye of history, they were the myopic prelude to the Great Depression. In his own day, Harry Truman was an accidental president, a pipsqueak who couldn’t fill FDR’s shoes. In the long eye of history, he is regarded as one of our most successful presidents, navigating the sticky post-war period internationally, and helping propel an economic boom domestically.

Predicting the historical long view is a risky proposition, but let me hazard a guess: Historians will wonder what bizarre convulsions this nation was going through — how it seemed to lose its moral, political, and economic bearings, how the gains of social and economic equality that were a century in the making were reversed, and, above all, how the country actually became less democratic, often with the acquiescence of many ordinary Americans.

The first thing historians are likely to fasten on is the historic economic inequality in America today. As the French economist Thomas Piketty has documented in his pathbreaking book, “Capital in the 21st Century,” America, the vaunted land of opportunity, has become one of the most unequal nations in the history of the world when it comes to wealth distribution — a country in which the top 1 percent own nearly 40 percent of the nation’s wealth....