Dharma combat is a dialogue between a Zen student and a Zen master, or two masters or advanced students, that demonstrates their understanding of the truth. The old dialogues contain many marvelous exchanges of this sort. Let me unpack one of them so that you can experience the thrill of dharma combat. (I chose this one, Case 21 from the Book of Serenity, because it is a particularly clear example, but there are hundreds of dialogues that would have served my purpose just as well.)

Dramatis personae: Yün-yen and Tao-wu, fellow students of Zen Master Yao-shan. They lived in the 8th to 9th century, and both monks later became great Zen masters.

Yün-yen was sweeping the ground. Tao-wu came up to him and said, “You look awfully busy.”
Yün-yen said, “There’s someone who isn’t busy.”
Tao-wu said, “If so, there’s a second moon.”
Yün-yen thrust out his broom and said, “Which moon is this?”
Tao-wu turned around and left.
Later, when this was told to Zen Master Hsuan-sha, he answered, from the position of Tao-wu, “Precisely the second moon.”

When our dialogue begins, Yün-yen is sweeping leaves outside the temple buildings—one of the daily tasks that every monk performs, however dull or enlightened he may be. I like to imagine Yün-yen in his early thirties. Many years before this, he experienced a major spiritual opening, and now his mind is clear. The broom goes back and forth. The leaves gather themselves into piles. Nothing else is happening. The whole universe has become the movement of one willow- twig broom sliding across the dry ground.

Into this rhythm Tao-wu intrudes. He is 11 years older than Yün-yen. He has a brilliant mind, and he enjoys verbal tussles with his younger brother-monk, who is a worthy opponent. So he says, “You look awfully busy.” On the surface this seems like a casual comment. But it has a subversive, Coyote-like energy to it. It’s meant to stir things up. It’s the ladle in the soup pot. It’s the opening move in the chess game. It’s the puppy running up to another puppy and stopping short, head hunched down, with its tail in the air. “Wanna play?”

Yün-yen could have nonchalantly responded to Tao-wu’s statement with a “Yes” and gone on sweeping. But what fun would that have been? Besides, he isn’t busy. He’s the opposite of busy. He is totally focused on the task at hand, but at the same time he’s a man of absolute leisure, who has nowhere to go, nothing to do. He’s not a cause; he’s an effect, and he just lets the sweeping take care of itself. So he says, “There’s someone who isn’t busy,” meaning himself, or more precisely, the not-self that takes care of the sweeping. This is a profound statement, worthy of being inscribed in gold on the temple wall and on the walls of every business and government building in the world. To discover, in you, as you, the someone who isn’t busy when the you you think you are is busy, who isn’t upset when the you you think you are is upset, is to discover a great freedom.

The only person Tao-wu sees is a monk who is sweeping the ground, doing his job as any responsible workman would. So why talk about someone who isn’t busy? Who would that invisible someone be? Where would he be? Is he standing over Yün-yen’s head in some ethereal form? Is he hiding inside his body as an unperceivable essence? Is he separate from him, in some transcendent Platonic realm of reality that is realer than this here-and-now? How ridiculous! Why multiply the facts? So, running to the metaphorical ball with miraculous speed, Tao-wu blisters it back over the metaphorical net with “If so” (that is, “if there’s anyone here besides you, my friend”), “there’s a second moon.” Occam’s razor, Zen-style.

You might think that this response would be the end of the dialogue. It awakens Yün-yen from what might seem his airy dream of transcendence. It punctures the Thanksgiving Day parade balloon of an inner buddha. It’s devastating, irrefutable.

Yün-yen, however, is unfazed. He thrusts out his broom, right in Tao-wu’s face, and says, “Which moon is this?” An unanswerable question-as-answer! It immediately changes the rules of the game. It pulls the rug from under Tao-wu’s feet, and the ground from under the rug, and the earth from under the ground. Amazing! How can it possibly be countered?

Let’s pause for a moment to recap the logical steps: The apparently busy monk is the first moon. The someone who isn’t busy is the imperceptible, marvelously redundant second moon. And the broom? Well, before it was thrust into the discussion, it was just doing its job, scratching the dry ground, sweeping the leaves into a succession of neat piles.

Naturally, Tao-wu declines to respond. The question has answered itself. All he needs to do in order to seal his triumph is walk away, leaving Yün-yen there unperturbed, complete, ready to start sweeping again, as alone and luminous as a full broom shining upon the earth from the depths of the night sky.

Here the dialogue ends.

But there’s a further twist. Years later, a traveling monk gave an account of the conversation to Zen Master Hsuan-sha, who was a connoisseur of finely tuned Zen dialogues. Connoisseurs of finely tuned Zen dialogues are usually content just to savor the excellence of what they have heard, but sometimes they can’t help getting into the act. Hsuan-sha refuses to let well enough alone. Tao-wu’s walking away was a masterstroke, he knows, but he sees another way of responding to Yün-yen, less subtle but equally emphatic. “Which moon is this?” is the question. “Precisely the second moon,” he answers, from Tao-wu’s position, with the imagined willow- twig broom staring him in the face. Ah, I knew it! There’s always room for one more. That someone who isn’t busy—I know him as well as I know you. He is you. Or would that be me? As long as there seems to be a you and a me, we might as well acknowledge it. We might as well enjoy it. And in fact, nothing could be more delicious.