It’s one of those things you learn when you first get a feel for politics: the things that count, that get stuck in people’s minds and affect real outcomes are not necessarily or even often the most important ones. They’re ones that resonate with basic, familiar or humorous parts of our common experience – like pyramids. I doubt very many people remember that Ben Carson also said that he believed that Satan encouraged Charles Darwin to write The Origin of Species, a claim that is at least as nuts as the pyramids comment and frankly, quite a bit more evil. But pyramids is different, even though it’s completely irrelevant to basically anything. Everybody knows about the pyramids. We know what they look like. We know pharaohs are buried in them. The very shape is elegantly simple and memorable. People wear pyramid hats sometimes to be funny. And most people know that they are basically solid stone. And you don’t need to be a genius to know that of all the places you might try to store grain, inside a rock would be one of the most challenging.

But there’s something else that I think is important about the pyramids flareup for understanding Carson and his candidacy. For his supporters, one of Carson’s greatest attributes is his soft-spoken humility. Yet what we really see in Carson is a compounding mix of ignorance and arrogance. Some of Carson’s views are rooted in his religious subculture. They may seem odd or even crazy to people outside of that subculture. But they’re different beliefs, not ignorance per se. But that’s not the case with imagining that pyramids are hollow and used for grain storage. As I noted Wednesday night, Carson not only doesn’t know what a pyramid is, he also thinks a notorious pseudo-science huckster is a representative of the views of contemporary science. It’s not the case with claiming that none of the country’s founders had experience in elected office – a demonstrably ridiculous claim. It’s not the case with claiming that half of Medicare spending goes to fraud. The exception that proves the rule came earlier this week when Carson conceded he really wasn’t familiar with US-Cuba immigration policy – a very striking gap in knowledge for a contender for the GOP presidential nomination.

But again, that’s the exception that proves the rule. When you watch Carson navigating the public square you see someone who is remarkably ignorant about huge swathes of human knowledge and particularly information about US government and public policy. But you also see someone who’s quite confident he’s very knowledgable. So he’s both remarkably ignorant and either stunningly unaware of his ignorance or totally indifferent to it. You might even say he is militantly ignorant. In all aspects of life, that is a dangerous combination. And the combination is almost always rooted in arrogance. None of us know everything. And in a complex world, we don’t need to. The key is having some realistic grasp of what you do know and what you don’t know.

That not only helps you avoid big mistakes and embarrassing gaffes, it also helps you learn. Because you can’t learn about things you think you already know.

One of the things that stood out to me about the pyramid debacle was “secular progressives” are welcome to ridicule his theory about the pyramids. But Carson really has no ‘theory’. He says that the ancient Egyptians stored grain inside solid rock. That makes no sense. Let’s try this again, how much of anything can you store inside a rock? It’s not a theory. It’s just coming up with an idea when you don’t know even the basic facts of what you’re talking about. I have to imagine this is rooted, at some level, in a life of being extremely knowledgable and one of the best practitioners in a highly specialized field of knowledge and extrapolating out from that that he is equally expert in any other field of knowledge.

Again, the issue here is less ignorance than arrogance, something which, paradoxically, many of Carson’s supporters believe is a bad trait he lacks.