I have come to the conclusion that Ben Carson is a bit nuts. I say that not because I disagree with him politically, but because he doesn’t seem to know what the truth is. Donald Trump, in contrast, does. When challenged, he becomes more forceful. He exhales a gale of fibs and just shoulders his way through until his interrogator surrenders. Carson, though, is unusually serene. He gives me the willies.

By now we know to distrust what Ben Carson says about Ben Carson. He did not, as he has written, turn down a full scholarship to West Point. Not only is there no such thing — West Point, like all the military academies, is free — but there is no record he ever applied. He said he was urged to do so by Gen. William Westmoreland, the former commanding general in Vietnam. This meeting took place in Detroit. There is no record of Westmoreland being in Detroit that day.

Carson has written that he once attempted to stab a friend in the belly. He now says that his purported victim was a “close relative,” but the man has not stepped forward and cannot be found. Carson says he protected white students in the Detroit riots that followed the assassination of Martin Luther King Jr., but these students, too, have evaporated upon examination.

The accumulation of exaggerations, fables and inventions is troubling — or would be if Carson was, in other ways, suitable for the presidency. He is not. He has no political or government experience and his knowledge of foreign policy comes down to this: He has none.

The New York Times recently had a useful article on the assorted lies of this political season. It began with Carly Fiorina’s exhortation to the many doomed employees of Hewlett-Packard about how the company was created. It moved from there to Trump’s denial that he ever called Marco Rubio the “personal senator” of Mark Zuckerberg even though those very words could be found on Trump’s website. (Why is it worse to be in Zuckerberg’s pocket than the Koch brothers’?)

The piece then proceeded to Hillary Clinton and some of the things she’s said about her personal email account and then wound up with Gary Hart and, of course, Bill Clinton, who lied about being a liar. This is a very rich topic, encompassing just about all history, including the Eisenhower administration’s announcement that the U-2 spy plane shot down over the Soviet Union was gathering weather data. Pilots of weather planes are not expected to kill themselves to avoid capture.

Carson has struck back in a so’s-your-mother fashion. He has accused the media of being both cynically and secularly distrustful of him while having given Barack Obama a free ride when he was a candidate. This is not the way Obama would see it. He was questioned about his mad pastor, his middle name and even his birthplace. Had Carson looked down the debate dais, he would have seen The Donald himself who, in his own telling, dispatched private investigators and possibly the doormen of his Fifth Avenue building to prove that Obama was not born in Hawaii, but in Kenya or someplace. How’s that for scrutiny?

Things have gotten to the point where, when I saw a Politico story headlined “The Man Who Pretended to be Ben Carson for 21 Years,” I thought the article was about Carson himself. It turned out to be about Prince Havely, an actor who has played Carson in a Baltimore area children’s theater production of “Ben Carson, M.D.” Maybe Havely would like to run for president. He could do a passable Ben Carson. It turns out, Carson cannot.

Richard Cohen is a columnist for The Washington Post. His email address is: cohenr@washpost.com.