I’ll never forget the first time I understood, in my bones, how conspiracy theory works. It’s like understanding a drug — you can’t, really, until you’ve been high on it. It was four years after 9/11, and I was having dinner at a Thai restaurant that was empty save for myself and a friend and a trio of middle-aged men who were seated at a nearby table. They overheard our conversation — about the Iraq War, the media, etc. — and chimed in.

After a few minutes, one of them declared, quite casually, that 9/11 was an inside job, and the three began to explain how it all happened. I’d never paid much attention to 9/11 conspiracy theories, so this became an informal introduction, and I was struck by how levelheaded and informed the men sounded; they weren’t overheated crackpots. Intrigued, I went home and Googled “9/11 conspiracy theory,” and that’s when I got sucked in, linking to surprisingly complex and intricate analyses, one leading to another (with a lot of blueprint illustrations), of where, exactly, the explosives had been planted in the World Trade Center, and how it all went down, and why it happened.

I began my odyssey of discovery around midnight, and though I occasionally glanced up at the clock, it was as if time was standing still. Before I knew it, the sun had come up, and there was a period, for about an hour or so, when I not only slipped down the rabbit hole but felt like I’d glimpsed the light of revelation on the other side. During that hour, I was a convert. I believed that forces within America had conspired to blow up the World Trade Center. Was it horrifying? Are you kidding? It was one of the most exciting feelings I had ever known. The uncanniness of it! The diabolical audacity. The sheer staggering fact that it had happened. I was horrified, but more than that, I was amazed.

And then I woke up.

Or, more accurately, I got some sleep and saw, the next day, that the thriller I’d been sucked into was a paranoid vision that melted down, like a vampire, in the light of reality. But I’ve never forgotten the high it gave me. It brought back the feeling I’d had as a teenager in 1975 when I, along with a great many other Americans, first saw the Zapruder film, on an ABC news special hosted by Geraldo Rivera, and became possessed by it. It brought back the feeling that our political life was a maze of hidden treachery, and that if you found a way to navigate the maze it would unfold with the clarity of a dream, and that understanding it all, knowing what had happened, would set you free.

The release, last week, of some of the last remaining documents in the JFK assassination files (even though the “good stuff,” as we learned, will be held back for at least another six months) is sure to provoke a new wave of theorizing about the events of Nov. 22, 1963. Back in the ’80s, the enlightened JFK conspiracy buff gravitated to scenarios that fingered the Mob. These days, the smart money, abetted by books like “JFK and the Unspeakable,” published in 2008 by the Catholic theologian James W. Douglass, says that the American security state, led by forces within the CIA, conspired to get rid of JFK because he wasn’t enough of a Cold War hawk. Since the files also shed new light on Lee Harvey Oswald’s 1963 trip to Mexico, where he visited the Cuban and Soviet embassies, Oswald’s image as the underground Zelig of the early ’60s — a nihilistic left-wing gun-nut zealot whose political orientation is as hard to pin down as his itinerary or his mental state — should only be enhanced.

The JFK documents are about things that took place in the real world. Yet the JFK assassination, or at least the theories about it, have long since morphed into something else. They’ve become pop culture, and I don’t just mean because Oliver Stone made a famously electrifying and influential movie about them. Conspiracy theory has become its own hall-of-mirrors version of docu-fiction. It’s the stories we tell ourselves, built around highly selective and insidious dollops of information.

What we know now, in a way that we didn’t 25 years ago, when “JFK” was released, is that the whole quality of conspiracy theory can radically change color. It began as a dogged search for truth, emerging from voices of the liberal-left. In 1963, the killing of JFK was a — literally — blurry event, which is why it launched the metaphysical enigma of the media age: The more you see, the less you know. It was said that the truth of the JFK assassination got covered up, and the impulse to uncover it amounted to righteous, anti-authoritarian muckraking. As long as conspiracy theory clung to it, debating what actually happened that fateful day in Dallas seemed a sane, responsible thing to do.

But conspiracy theory means something very different today. It has mutated into a worldview of often astonishing recklessness, an unending spasm of anti-bureaucratic wrath — and into a justification for fake news, since if we can’t know the truth, then “real” news, by definition, is as fake as anything else. The spread of conspiracy theory has made reality, for a lot of people, seem like a daily abyss. You could argue that it’s become America’s first nationalized mental illness.

Conspiracies can be real, of course. Watergate was, and so was the notion that the administration of George W. Bush launched the Iraq War because it actually believed there were WMDs there. (Yeah, right.) The connections between the Trump campaign and the Putin government may or may not yet rise to levels of conspiratorial collusion.

In that light, it’s tempting to say that the JFK assassination theories have a fundamental validity, while the theories that Vincent Foster was murdered or that 9/11 was an inside job do not. Yet those who would draw such a distinction are perhaps a bit too eager to fudge what it all has in common. Namely: Every conspiracy theory is a metaphor. Each is an intricate narrative that lends shape and order to the world.

The latest treasure trove of JFK documents will be pored over in microscopic detail, but those doing the poring, searching for the skeleton key that will unlock the truth of our world, rarely acknowledge the irony that the old left, through JFK conspiracy, helped to spawn the new right. The Deep State plotted to get rid of John F. Kennedy: That was, and still is, a metaphor for how any number of sophisticated progressives feel about the nature of our government today. U.S. government “globalists” plotted to blow up the World Trade Center: That’s a metaphor for how more than a few supporters of Donald Trump, following that Pied Piper of delusion Alex Jones, think the swamp of Washington works. Can you have one theory without the other? We now have an answer: No.

Since the last JFK files are being unsealed, if you want to locate the skeleton key to reality, I would say don’t bother immersing yourself, yet again, in the seductive arcana of bullet trajectories and second and third gunmen and the shadow alliances of the early ’60s. It’s almost certain to lead nowhere. I advise you, instead, to see a movie that addresses both the JFK assassination and the psychological tentacles of conspiracy theory. It’s called “Oswald’s Ghost,” made in 2007 by the documentarian Robert Stone, and it’s a revelatory work of dramatic journalism that leads you straight into the looking glass and out the other side.

Much of “Oswald’s Ghost” is devoted to how compelling, and necessary, the JFK assassination theories were. Robert Stone sucks you in as powerfully as Oliver Stone did, showing you how the information added up to a vortex, a scenario with too many holes not to be filled by conspiracy. Stone interviews Mark Lane and Robert Dallek, but the film’s most powerful presence is that of Norman Mailer, interviewed not too long before his death; he becomes its bard of reality-based eloquence. Mailer was one of the great believers in the theory that Lee Harvey Oswald did not act alone, but he emerged from that belief like a snake shedding its skin. In “Oswald’s Ghost,” Mailer’s dissection of Oswald is more haunting than any conspiracy, and he traces his own progression, from conspiracy theorist to lone-gunman rationalist, like a journey of the soul.

It has often been said that the idea that Oswald acted alone was too disturbing for people to accept, because it meant that one trivial lunatic could alter history. Yet if that is, indeed, a threatening notion, you could argue that the alternative — the theory that he was just the tip of the iceberg — became, in its way, one of the most destructive ideas of the 20th century. Conspiracy theory once felt chancy and bold: the ultimate challenge to the status quo. But it devolved, over the decades, into a borderline lazy, armchair-protest form of kissing off the establishment. Our culture now sells conspiracy theory by the yard. It has become a franchise of the imagination, with a scandalous sequel every week. A few conspiracies, of course, are real, but it’s time we considered that the ultimate conspiracy may be the one that conspires to keep us passive and helpless by getting us to see conspiracy everywhere we look.