Donald Trump has many serious flaws, including incorrigible dishonesty, rampant narcissism, contempt for women and a fashion sense that makes him think that hairstyle of his is flattering. But nothing compares to his most prominent, crippling and incurable defect: He’s dimmer than a 5-watt bulb.

Secretary of State Rex Tillerson was reported to have called the president a “moron” — emphasizing that term with an adjective I can’t repeat here. Forced to hold a news conference to praise the president’s intelligence, Tillerson was too honest to deny what he had said.

The late William T. Kelley, who taught Trump at the University of Pennsylvania, said, “Donald Trump was the dumbest goddamn student I ever had.” Tony Schwartz, the ghostwriter of “The Art of the Deal,” says Trump had “a stunning level of superficial knowledge and plain ignorance.”

Trump’s feeble-mindedness is on daily view. When an Uzbek immigrant was arrested for allegedly driving a truck down a Manhattan bike path, killing eight people, the president responded in thunderously stupid ways. First, he tweeted that he had “just ordered Homeland Security to step up our already Extreme Vetting Program.” If you can step it up, why didn’t you do that before?

-snip-

The evidence of his dimwittedness flows as continuously and voluminously as the Mississippi River. His tweets are studded with misspellings, random capitalizations and mystifying quotation marks.

He taps out tweets that flagrantly contradict what he tweeted when Barack Obama was president, making himself look ridiculous. When he holds forth on policy issues, it’s excruciatingly apparent he has no idea what he’s talking about.

-snip-

Trump tries to conceal his intellectual deficiency by insisting how smart he is. “I went to an Ivy League college,” he said last month. “I’m a very intelligent person.” He has to make such affirmations because all the evidence indicates his cranium contains an airless void.

-snip-

I’m sure plenty of readers are now saying I’m the stupid one, with a brain far inferior to Trump’s. They may be right. So I put a challenge to him: We both take an IQ test, administered by an independent body, with the results to be made public.

-snip-

But I’m betting Trump will never submit to any process that would document his actual intelligence for the public to see. He’s dumb. But not that dumb.