President Donald Trump is a terrific leader, if he does say so himself. There’s never been a commander-in-chief so prone to extravagant self-praise, which is all the more striking given the paucity of his achievements to date. “We’ve done a great job,” he told reporters on Friday. “We’ve done a great job in Puerto Rico.” Later that day, he tweeted what “a wonderful statement” from “the great” Lou Dobbs, a host on the Fox Business Network: “We take up what may be the most accomplished presidency in modern American history.” In interviews, Trump is eager to tout accomplishments that, quite frankly, don’t even make any sense, as when he claimed in an interview on Wednesday with Fox News’ Sean Hannity that the rise in the stock market can be seen as offsetting the national debt.

Trump’s relentless self-promotion is one of his most consistent character traits, which can be traced back to his earliest days as a real estate mogul. In always tooting his own horn, Trump is a familiar American type: the eternal salesman, a hustler who won’t take no for an answer and will say anything to close a deal. Being relentlessly on the make, for someone like Trump, isn’t just a job; it’s a vocation. And that vocation is fueled by a theology of positive thinking.

As a number of observers have persuasively argued, Trump is guided by a particular gospel. Though he’s more secular than any of his predecessors, he has genuine roots in one particular strand of Protestantism. He grew up attending the Marble Collegiate Church in Manhattan, which was presided over by the Reverend Norman Vincent Peale, the author of one of the all-time bestselling self-help books in American history: The Power of Positive Thinking. In 1977, Peale would marry Trump to his first wife, Ivana.

While Trump has only the most rudimentary knowledge of the Bible, he often echoes Peale’s core lesson: that happy thoughts and cheerful chatter are the key to success. “Formulate and stamp indelibly on your mind a mental picture of yourself as succeeding,” Peale wrote in his best-seller. “Hold this picture tenaciously. Never permit it to fade. Your mind will seek to develop this picture. Never think of yourself as failing.” In a 1983 interview with The New York Times, Trump echoed Peale’s dogmas. “The mind can overcome any obstacle,” the young Trump said. “I never think of the negative.” In his campaign book Crippled America, Trump wrote, “Reverend Peale was the type of minister that I liked, and I liked him personally as well. I especially loved his sermons. He would instill a very positive feeling about God that also made me feel positive about myself.”

Trump might feel positive about himself, but not about the world around him. As a candidate, and even as a president, he has often used dark, frightening rhetoric to portray America as a land where ordinary people are betrayed by a globalist elite and exploited by cunning foreigners and vicious immigrants—the most memorable exampled being his “American carnage” inaugural address. He also concocts derisive nicknames for his political enemies, most recently going after “Liddle” Bob Corker. But this seeming contradiction between the mantra of “positive thinking” and Trump’s nasty, apocalyptic rhetoric is best understood as two sides of the same sales pitch: The world is a mess, and “I alone can fix it.” Trump’s portrait of an America in deep decline was a necessary predicate to winning votes and now, less successfully, to maintaining support, the logic being that the U.S. was in such dire straits that it’s worth the risk to trust Trump.