“It ain’t what you don’t know that gets you into trouble. It’s what you know for sure that just ain’t so.” — Mark Twain (probably?)
The above quote is a wonderful self-referential example of itself. When I was thinking of it and looked it up, I was quite certain that it was from Mark Twain. But on review, that isn’t certain. So, let’s add this one to the list of things we need to be careful of.