His inability to focus his attention makes it hard for him to learn and master facts. He is ill informed about his own policies and tramples his own talking points. It makes it hard to control his mouth. On an impulse, he will promise a tax reform when his staff has done little of the actual work.

Second, most people of drinking age have achieved some accurate sense of themselves, some internal criteria to measure their own merits and demerits. But Trump seems to need perpetual outside approval to stabilize his sense of self, so he is perpetually desperate for approval, telling heroic fabulist tales about himself.

“In a short period of time I understood everything there was to know about health care,” he told Time. “A lot of the people have said that, some people said it was the single best speech ever made in that chamber,” he told The Associated Press, referring to his joint session speech.

By Trump’s own account, he knows more about aircraft carrier technology than the Navy. According to his interview with The Economist, he invented the phrase “priming the pump” (even though it was famous by 1933). Trump is not only trying to deceive others. His falsehoods are attempts to build a world in which he can feel good for an instant and comfortably deceive himself.

He is thus the all-time record-holder of the Dunning-Kruger effect, the phenomenon in which the incompetent person is too incompetent to understand his own incompetence. Trump thought he’d be celebrated for firing James Comey. He thought his press coverage would grow wildly positive once he won the nomination. He is perpetually surprised because reality does not comport with his fantasies.