But there are differences now that make the cranks that much more baffling, numerous and pernicious. For starters, they fly ever more stubbornly in the face of sophisticated research and hard-earned knowledge. Beneficiaries of wisdom that prior generations lacked, they toss it away, wasting and mocking progress itself.

At the same time, in many educational circles, there’s as much talk of students’ individual truths as of the truth. Joan Donovan, the director of the Technology and Social Change Research Project at Harvard’s Shorenstein Center, said that social science and history courses increasingly emphasize that truth is situational and that “very few things are always true all the time.” That healthy skepticism can turn unhealthy when it leads to the rejection of incontestable realities. There’s “a crisis of authority, a crisis of expertise,” Donovan told me.

There’s also a man in the White House, at the Resolute Desk, who makes grand pronouncements based on random conversations; implores Americans to distrust traditional institutions and conventional sources of information; and promotes conspiracy theories (millions of illegal votes, a celebration among Muslims in Jersey City on 9/11, and on and on). He has specifically echoed and validated the apprehensions of anti-vaxxers. Whether he’s symptom or cause doesn’t matter. He’s dangerous either way.