
Two of the most famous and important sayings of Zen come from the first koan in the Mumonkan, the Gateless Gate collection of Zen dialogues that point to the wisdom of emptiness and the manifestation of compassion. The fact that it is the first case and also about Bodhidharma, the revered Zen ancestor who brought Zen to China from India and was also famous for years of sitting facing a wall, emphasizes its importance as well.
When Emporor Wu asked Bodhidharma about the highest of holy truths he said "Empty, without holiness". This is the foundation of prajna and buddha nature as well as the Zen emphasis on a level playing field in Reality where nothing is special. "When you meet the Buddha kill her" and the tossing of a Wooden Buddha into the fire are other enactments of Shunyata, the ground of being and nuomena. In the Suzuki Roshi lineage of Zen, we emphasize the Zen sitting posture itself is a manifestation of Buddha nature, the universal nature that runs through all things and out of which the world of form and color appear, the phenomena of existence. When everything is without holiness, everything is sacred. In meditation practice you learn to settle the mind and body as a means of cultivating alertness and presence, the soil of beginner's mind.
The other quintessential response of Bodhidhamra to the question 'who are you?' was 'I don't know'. This phrase and comprehension has resounded through Zen for millennium and is the root of the Bodhi tree. We spend our lives trying to define ourselves, to establish an identity based on certainty, conviction, and conditioning. Zen simply takes it all away and doesn't replace it. This is the humble ground of just being somebody, an ordinary person that lives and dies, like all things and with all things. Zen is a steep cliff because of necessity we keep falling off it without a parachute. Refining your life in Zen means continually returning to ground zero, a place of not knowing, the fertile ground of being awake.
Ask all you want,
It remains unknown.
Can you swallow the moon?