A wise man once said the more we know in the world, the more we realize there is so much that we do not know. So, based on that, one that thinks they know everything knows very little.
There are these people, a type of know-it-all, who don't dare say they know everything but claim they know all there is to know. Do they? I doubt it. Some day, they will realize that the world does not revolve around their little, pathetic lives.