Fear induces herding behavior. For my last column I went back and read some profiles of Joe Biden written in the 1970s and 1980s. I was stunned to see how free-flowing they were, how little the authors were tied down by ideological rigidity and tribal mentality. I was reminded how much we’ve all clenched up, how much we all now seem to be members of this or that cult — fearful of saying something “wrong,” fearful of provoking a Twitter backlash, mindlessly repeating the clichés that signal to others that we are faithfully staying within the barricades of our tribe.

Fear revives ideology. The 20th century saw a clash of iron-grip ideologies. Then, about 10 years ago, we seemed to be entering the age of the data wonks. The students in my classes didn’t have faith in all-explaining dogmas. Skeptical, they just wanted the evidence.

But now grand ideologies clash by night: white nationalism, populism, oppression studies. All trade in binaries between oppressor and oppressed, the struggle between the good groups and the menacing evil ones.