"There’s two kinds of ignorance...."

"There are two kinds of mistakes. There’s two kinds of ignorance. There’s the things we don’t know, and then there are the things we think we know, that aren’t true. The things we know that we don’t know -- that we wish we understood, we wish we had access to the truth. There are things we think we’ve discovered as true that, in fact, are not. And that was the focus of that piece."

~ Russ Roberts summarising Hayek's Nobel-Prize acceptance speech 'Pretence of Knowledge,' i.e., "that piece"