"The word translated, koan, it means a problem. But it's a very special problem. And to strip it down to the way it works, you are given a problem which has no rational solution. There is a contradiction built into it. One standard - one is this is the sound of two hands clapping. What is the sound of one hand clapping? And so on. All right, so the first thing is that it brings your rational mind to an impasse."