A monk asked Joshu in all earnestness: “Does a dog have Buddha-nature or not?”
Joshu answered: “Mu.”*
*In Chinese, “Mu” can be read as a negative answer: “No,” “No way,” “Not at all.” But as the compiler’s comment below makes clear, this way of reading would not get to the import of the koan. It is an answer that invites the practitioner to go beyond conventional meaning, and be opened to an entirely new horizon of seeing things.
Mumon’s comment: To realize Zen one has to pass through the barrier of the ancestors. Enlightenment comes once the path of discursive thinking is blocked. If you do not pass this barrier of the ancestors, or if your discursive mind is not blocked, in whatever you think and whatever you do you are like a wandering ghost. You ask: What is the barrier of the ancestors? This one word is it: Mu.
This is the barrier of Zen. If you pass through it you will meet Joshu face to face. You can then walk hand in hand with the whole line of ancestors. Is this not a joyful thing to do?
If you wish to pass this barrier, you must work on it with every bone in your body, through every pore of your skin. Keep it with you day and night, and penetrate through this question: What is Mu? Do not think it is the usual negative character meaning “nothing.” No, it is not Nothingness, the opposite of Being. If you really wish to pass this barrier, you are like one who has swallowed a hot iron ball and can now neither swallow nor spit it out.
Now all your previous knowledge falls away. As a fruit ripening in season, the subject and object naturally become one. It is like a mute person who has had a dream, knowing it intimately, but cannot speak about it.
When one enters this condition the ego-shell is crushed and one walks freely between heaven and earth. You are like a great warrior with a sharp sword. If a Buddha stands in your way, you will cut him down. If an ancestor presents any obstacle, you will kill him. You will be free from the cycle of birth and death. You can enter any world as your own playground. Let me tell you how to do this with this koan:
Just concentrate your whole being and energy into this Mu, and do not allow anything to keep you from it. When you enter this Mu and there is no separation, your realization will be like a bright torch burning and illuminating the entire universe.
Perfect manifestation, absolute command.
A little “has” or “has not,”
Life and body, all is lost.
This is the first of forty-eight (48) koans in a well-known collection compiled by a thirteenth century Chinese monk, Wu Men (Mumon in Japanese pronunciation), entitled Wumen Kuan (Mumonkan), or Gateless Barrier ( a play on the meaning of the characters of the compiler’s name.) A koan, literally a “public case,” is given by a Zen Master to those who manifest earnestness in practice and are deemed ready for an experience of the realization of their Buddha-nature, or their True Self.
Mumon’s own commentary provides a helpful guide to what is expected of a practitioner who is given this koan. During seated meditation (zazen), one is enjoined to focus one’s entire awareness on this “barrier of the ancestors,” that is, Mu (pronounced Wu in Chinese), accompanying the outbreath with it repeatedly, and letting oneself be totally absorbed in Mu. As one deepens in a state of unitive awareness (samadhi), the separation between “subject” and “object” is overcome, and at a ripe moment, an entirely new horizon emerges. This is the moment of kenshō, literally, “seeing into one’s True Nature,” whereby the practitioner is awakened to a world beyond the dualities of yes and no, having and not-having, being and non-being, life and death.
From this point on, the focus of Zen practice is to provide guidance in enabling this new horizon to shed light on every aspect of one’s being, in the cultivation of wisdom and compassion in one’s day to day life. Zen practice continues with subsequent koans that deepen, clarify, and further elucidate on this new horizon, enabling one to embody the world of nonduality or non-separation, in one’s mundane life.