Preserving the flexibility to pick and choose facts carries obvious strategic benefits. In the aftermath of the attacks of Sept. 11, President Bush and his senior aides wanted to be sure they received the intelligence they needed to justify their case for going to war in Iraq. They accomplished this by dismantling the information-filtering process that had been in place for decades. In its place, they created so-called “stovepipes” that fed raw intelligence from the field directly into the White House, thus routing around layers of professional analysts. Those bypassed analysts might have noted that much of the intelligence underpinning the administration’s assessment of Iraq’s weapons of mass destruction came from completely unreliable sources. Or they might simply never have passed on the intelligence in the first place.

But why accept someone else’s truth when you don’t have to? In 2002, a “senior adviser” inside the Bush administration told the journalist Ron Suskind (for an article later published in this magazine) that the mainstream media were part of “the reality-based community,” which he defined as people who “believe that solutions emerge from your judicious study of discernible reality.” But that’s not the way the world works anymore, the adviser explained. “We’re an empire now, and when we act, we create our own reality.”

The adviser’s airy dismissal of discernible reality was weird and shocking when it was published in 2004, but today it feels a bit naïve. In the age of Trump, you don’t need to act to create your own reality; you can just tweet, whether it’s bogus crime and unemployment statistics or made-up accusations of widespread voter fraud. For that matter, you don’t even need to tweet; you can just retweet. In a world with no universally recognized standards for truth — a world in which journalists engaged in the study of discernible reality are dismissed as “dishonest” and “corrupt” — everything is fair game. Maybe Clinton’s campaign chairman takes part in occult rituals in which bodily fluids are consumed, maybe he doesn’t. Who’s to say, really? “U decide,” as the incoming national-security adviser, Mike Flynn, wrote in a tweet with a link to a post claiming that Clinton’s hacked emails contained enough evidence to put her away for life on charges including “sex crimes with minors.”

In the age of Trump, data and evidence are just some unwanted roughage down at the end of the buffet. Bush may have taken a selective approach to intelligence, but Trump, in his ongoing self-investigations, ignores it altogether, rejecting the daily national-security briefings traditionally provided to presidents-elect by the C.I.A. Even speaking under the cover of anonymity in a completely unguarded moment — is there such a thing as a guarded moment for Trump? — it’s impossible to imagine him drawing a line between “the reality-based” world and the conspiratorial world of self-investigation that he and his fellow travelers inhabit. It’s a distinction that he doesn’t recognize.

Edgar Welch was different. At a certain point, he stopped looking at the internet. All his hours in the Pizzagate feedback loop ultimately drove him not deeper down the rabbit hole, but out into the real world, where he could do some primary research. He was concerned that something very bad was happening in that pizzeria in Washington. When he decided to check it out for himself, and maybe even do something about it, Welch the self-investigator became an actual investigator, albeit a badly deluded, dangerous one. What he discovered — though not before he had fired off a couple of rounds, frightening a lot of people and possibly landing himself in prison for several years — was that he had been gorging on a lot of lies. Or, as he later told a reporter for The New York Times, coining another memorable phrase for our age, “the intel on this wasn’t 100 percent.” That, at least, was 100 percent true.