Sometimes you think you know, but you don't. Oh sure, you'll be all, "I know," and people will be all, "really? do you?" and you'll be all, "of course I do." But you don't, and you are starting to realize it, and then, just like that, you fool yourself. You may know some infinitesimally small part of it, but not even enough to do the edges of the puzzle, and yet you'll be all, "look! look! who has a blue piece?" That's when the kids laugh, and usually, they're right.