If you’re despondent over the election, consider this reminder from F. Scott Fitzgerald: “The test of a first-rate intelligence is the ability to hold two opposed ideas in mind at the same time, and still retain the ability to function.”

The “opposed ideas” we need to juggle simultaneously concern who we are as Americans - a multiracial, multicultural nation coming to terms with our galloping diversity, or an us-against-them nation more torn apart by race, age, gender, geography, immigrant status and socioeconomic circumstance than at any time in living memory.

That second idea has had a trium...