And you can solve a koan only when you have fallen into deep ignorance, not before it, because a koan is not a puzzle. Or if it is a puzzle, then it is not an ordinary puzzle. An ordinary puzzle can be solved by the mind; if you put your mind to it you can find a way to solve it; it has a solution. A koan is such a puzzle that it has no mind solution possible; you cannot solve it. It is not a question of what you do, it is insoluble. Mind cannot give any answer to it.
For example, Zen masters say, “Listen to the sound of one hand clapping.” Now, one hand cannot clap, and unless it claps there will not be any sound, so to what are you going to listen? The mind will work out many solutions, and all will be meaningless, and the master will send you back again and again. Again listen. Meditate. The solution will happen one day when the mind disappears. When you work hard with the mind and the mind finds no way to reach any solution, out of sheer tiredness the mind falls flat on the ground. Suddenly you are in a state of no-mind, and you hear the sound of one hand clapping.
The mind hears only the sound of two hands clapping be cause the mind lives in duality. The mind can hear only a created sound. When the mind disappears, you hear the soundless sound, what the Hindus call anahat nad. The word anahat means exactly the same as what Zen people call the sound of one hand clapping. If you clash two things there is a sound that is called ahat nad, a sound that comes out of conflict. And there is a sound permeating existence itself – which is not created, uncreated. When you become so silent that the mind has disappeared, disappeared with all its noise, suddenly that soundless sound is heard, that aumkar, that anahat nad is heard. But that happens only when the mind has gone.
Traditionally Zen monasteries will only admit wandering Zen monks if they can show proof of having solved a koan.
It seems that a monk once knocked on a monastery gate. The monk who opened the gate did not say “Hello” or “Good morning” but “Show me your original face, the face you had before your father and mother were born.”…
This is a koan. And the host is asking the guest to show some sign that he can solve a koan; otherwise he is not worthy of being allowed to stay in the monastery; then he will have to go away.
…The monk who wanted a room for the night smiled, pulled a sandal off his foot and hit his questioner in the face with it. The other monk stepped back, bowed respectfully, and bade the visitor welcome. After dinner, host and guest started a conversation, and the host complimented his guest on his splendid answer.
“Do you yourself know the answer to the koan you gave me?” the guest asked.
“No,” answered the host, “but I knew that your answer was right. You did not hesitate for a moment. It came out quite spontaneously. It agreed exactly with everything I have heard or read about Zen.”
The guest did not say anything, and sipped his tea. Suddenly the host became suspicious. There was something in the face of his guest which he did not like.