To say that this is an era of disbelief means, quite literally, that millions of Americans no longer believe what they once believed. There is a loss of faith in old orthodoxies and the established “experts” who championed them. There are three areas where Trump suggests major departures from existing policies.

First, the economy. Despite a 4.8 percent unemployment rate, the recovery from the 2007-2009 Great Recession has been middling. The number of payroll jobs, 145.5 million in January, was only 5 percent above the level in January 2008, the peak in the previous economic expansion. Millions of workers have dropped out of the labor force, notes Nicholas Eberstadt of the American Enterprise Institute. Gross domestic product (GDP) — the economy’s output — has been growing only about 2 percent annually. The Trump administration believes it can raise that to 3 percent or more through lower tax rates, less regulation and more aggressive trade policies.

Second, the world order. Since the late 1940s, the United States has provided physical and economic security for our allies through alliances (NATO) and trade agreements. The collapse of the Soviet Union in 1991 signaled the success of this strategy and — it was said — marked the beginning of a long period of peace and prosperity, presided over by the United States. Trump is unsympathetic to this global role, which (he argues) burdens us with large costs in both blood and treasure. He wants trade agreements to be more favorable to us, and for our allies to pay for more of their defense.

Third, the welfare state.