Drawing a line is necessary: at some point, you have to declare that the Holocaust happened, that vaccines don’t cause autism, and that climate change is real. The philosopher Bernard Williams noted that science isn’t a free market of ideas but a managed one; without filters against cranks, trolls, and merchants of doubt, knowledge production “would grind to a halt.” But in science, and in intellectual inquiry more broadly, where you draw the line matters enormously. Keep things too open and you’re endlessly debating whether Bush did 9/11. Close them too quickly, though, and you turn hasty, uncertain conclusions into orthodoxies. You also marginalize too many intelligent people, who will be strongly encouraged to challenge your legitimacy by seizing on your missteps, broadcasting your hypocrisies, and waving counter-evidence in your face.
That could be the story of the past six decades. The nineteen-sixties started as a high point in trusting experts. John F. Kennedy was a popular Harvard-trained, Pulitzer Prize-winning author who stacked his Administration with intellectuals. Nearly four-fifths of Americans, when polled in the early sixties, said that they trusted the government to do the right thing at least most of the time. (That number now hovers near one-fifth.)
Not everyone basked in the light, though. In 1963, the historian Richard Hofstadter gave a perceptive lecture about the “paranoid style in American politics,” the tendency toward “heated exaggeration, suspiciousness, and conspiratorial fantasy.” The next day, J.F.K. himself turned to the topic. He warned of those who adhered to “doctrines wholly unrelated to reality” and spread “ignorance and misinformation.” Or at least he planned to issue that warning. En route to giving his intended speech at the Dallas Trade Mart, the President was shot twice and killed.
The man arrested, Lee Harvey Oswald, had defected to the Soviet Union and then, oddly, re-defected back to the United States. Oswald professed innocence—“I’m just a patsy,” he told the press—but was himself murdered before he could further explain. Was some larger plot afoot? “I thought it was a conspiracy and I raised that question,” Kennedy’s successor, Lyndon Baines Johnson, recalled. “Nearly everyone that was with me raised it.”
But a full, public airing threatened to reveal the C.I.A.’s machinations and the F.B.I.’s incompetence. Worse, intimations of foreign involvement might trigger a nuclear war, Johnson warned. He convened an investigatory body, the Warren Commission, to defeat these dangerous speculations. (He told one commissioner that forty million might die if accusations against Cuba and the U.S.S.R. weren’t refuted.) The point of the investigation, for Johnson, wasn’t to uncover new facts but to shore up the official story, which was that Oswald alone was guilty.