“Classic” conspiracy theories, according to Muirhead and Rosenblum, arise in response to real events—the assassination of John F. Kennedy, say, or the terrorist attacks of September 11th. Such theories, they argue, constitute a form of explanation, however inaccurate they may be. What sets theories like QAnon apart is a lack of interest in explanation. Indeed, as with the nonexistent child-trafficking ring being run out of the nonexistent basement, “there is often nothing to explain.” The professors observe, “The new conspiracism sometimes seems to arise out of thin air.”

The constituency, too, has shifted. Historically, Muirhead and Rosenblum maintain, it’s been out-of-power groups that have been drawn to tales of secret plots. Today, it’s those in power who insist the game is rigged, and no one more insistently than the so-called leader of the free world.

Donald Trump got his start in national politics as a “birther,” promoting the idea that President Barack Obama wasn’t born in the United States. Several news organizations have tried to keep track of the conspiracy theories Trump has floated since then. One list, posted by the Web site Business Insider, has nineteen entries. These include the claims that vaccines can cause autism and that Supreme Court Justice Antonin Scalia may have been murdered.