There are certain moments in politics that, when they occur, one immediately says, "Oh, we're going to remember that one." Often it's not because what happened had profound practical importance in and of itself, but because it encapsulated some deeper truth about a politician, a series of events, or the times in which we live.

One such moment occurred Monday, as President Trump addressed reporters alongside Israeli Prime Minister Benjamin Netanyahu, a moment that raised once again a profound question: How much of a problem is it that the president of the United States, the most powerful person on Earth, is a blithering idiot?

Here's what happened. During a chaotic moment with many people speaking at once, a reporter asked a question about Trump's passing on highly classified information to the Russian foreign minister and ambassador during an unusual Oval Office meeting, when in an apparent attempt to impress them, he boasted about how an ally of the United States had placed an operative deep within ISIS. The revelation set off a firestorm of criticism, but the original report was careful not to mention which U.S. ally it was.

Though rumors swirled about the identity of the U.S. ally, with many pointing to Israel, government sources wouldn't confirm it — until Trump hushed the assembled reporters and said, "Just so you understand, I never mentioned the word or the name 'Israel.' Never mentioned it during that conversation." Meanwhile, Netanyahu worked hard to keep a friendly smile on his face. "They were all saying I did," Trump went on (meaning the journalists), "So you had another story wrong. Never mentioned the word Israel." So in trying to tamp down the story that he revealed sensitive information to the Russians, Trump enthusiastically confirmed to the entire world that Israel was indeed the U.S. ally who had supplied the intelligence information. Nice work, Einstein.

One couldn't help but be reminded of what one anonymous source told CNN last week about why it's so difficult to prepare the president for sensitive meetings where national security information might be discussed but discretion is required. "You can't say what not to say," the source said, "because that will then be one of the first things he'll say."

Before he took office, everyone knew that Trump was the least prepared president in history. He had no political experience, and plainly took no interest in the details of policy or how government works. But that could be a choice — it's possible for a brilliant person to know nothing about politics and policy — and it was something that a sufficient number of voters actually found appealing.

To dispel any suggestion that he wasn't the sharpest tool in the shed, Trump regularly insisted that he possessed a powerful intellect. "I'm, like, a smart person," he said by way of explaining why he didn't need regular intelligence briefings during the transition. It was an echo of an earlier comment, when he said, "I have a very good brain and I've said a lot of things," as an explanation for why he didn't need foreign policy advisers. "Look, if I were a liberal Democrat, people would say I'm the super genius of all time. The super genius of all time," he said in 2015. Or another time: "I was a good student. I understand things. I comprehend very well, okay? Better than, I think, almost anybody." Or yet another time: "I'm very highly educated. I know words, I have the best words. But there's no better word than 'stupid.'" Indeed.

The idea that it's dangerous for the president of the United States to be a witless mouth-breather might seem self-evident. But the truth is that raw intellect doesn't translate to presidential success, and its absence could, in the right circumstance, be compensated for. Jimmy Carter was extremely smart, and his presidency was a failure in many ways. Ronald Reagan was no genius, but he had both a guiding philosophy and enough open-mindedness to change course when the situation demanded it, leading him to do things like raise taxes and negotiate with the Soviets.

No matter how smart the president is, he can't hope to have deep knowledge about all the issues he'll have to deal with. What the good ones have is a knowledgeable staff and experts they can trust to present them with the relevant information, and an ability to ask the right questions to guide their decision-making. Donald Trump doesn't seem to have any of these things. He hired a bunch of people without governing experience, and instead of knowing what he doesn't know, he believes he knows everything he has to.

For instance, after saying to much derision that he had discovered that "Nobody knew that health care could be so complicated," he later insisted that in helping House Republicans pass their Affordable Care Act repeal plan, "In a short period of time I understood everything there was to know about health care." Not even the most fervent Trump supporter could say with a straight face that that's true, since health care is one of the most complex policy areas there is, and there's no evidence that Trump grasps the first thing about it.

That gets to what makes President Trump's particular brand of stupidity so dangerous. You can be dumb but modest, or dumb but thoughtful, or dumb but careful. Trump is none of those things. He's boastful, impulsive, and careless, all while continuing to blaze new trails of thickheadedness, while the rest of us are left to stand back and gawp in amazement.

So far, all of his most vivid displays of idiocy have either put his own political fortunes in jeopardy (like practically admitting to obstruction of justice in a television interview) or caused only low-level international incidents. He hasn't yet been faced with a genuine crisis in which lives depend on his decisions. But he will sooner or later. And then we'll find out how dumb he really is.