Kong-ans (the Japanese call them koans) are those extremely brief stories (often just a few lines) and associated questions that are unique to the Zen tradition. No other school of Buddhism uses them. And Zen practice depends on them — these stories deliver Zen teaching far more than sutras do.
You can make kong-an practice sound very mystical but in fact it is very practical. We are always hit with situations whose basic assumptions are just plain wrong. But we’re socialized to go along with whatever misconception is at the root of the situation and not to cut through it. It’s like trying to untie the Gordian knot — you can’t. But Alexander the Great took his sword and cut through it. That wasn’t mystical. It was very practical. It worked.
Here’s an example. A long time ago in China a famous sutra master heard about monks in south China who only meditated and didn’t read sutras. He was outraged. So he travelled on foot for thousands of miles to show these monks their mistake. At one point he found himself in a small teashop. He was hungry and wanted to buy lunch. The owner (herself a Zen student) said to him, “You are a great Diamond Sutra master. Answer my question and you will have lunch for free. Otherwise, no lunch for you.” “Ask me anything,” the monk replied. “Okay,” the woman said. “The Diamond Sutra says that past mind cannot be grasped, present mind cannot be grasped, and future mind cannot be grasped. With what kind of mind will you eat your lunch?” The sutra master was stunned. He could not answer. All of his studying and lecturing couldn’t help him. He got no lunch. But the woman sent him to her teacher, and the sutra master eventually became the great Zen master Dok Sahn.
That is how kong-ans work. Just like Alexander and the Gordian knot, we are faced with something that our standard intellectual techniques cannot begin to deal with. We have to cut through with our mind sword. Over and over we have to find the appropriate mind sword to cut through the particular knot that is facing us. After a while we learn to do this not just in kong-an interviews, but in our lives. We learn to cut through the knots that bind not only us but everyone around us.