The Nun Miaoxin:
Little is known of Miaoxin's early life, except that she was born about 840 CE. Her nickname, Huaizi, "child of the Huai River," suggests she was born on the banks of the Huai, which flows west to east in central China. The name Miaoxin means "wonderful belief."
Her Place in the Lineage:
Miaoxin was a disciple of Yangshan Huiji. Yangshan was a dharma heir of Guishan Lingyou, which made him a dharma brother to the formidable "Iron Grindstone" Liu.
Yangshan held Miaoxin in such high regard he made her minister of secular affairs for his monastery. He said, "She has the determination of a person of great resolve. She is truly the one qualified to serve as the director of the office for secular affairs."
Flag, Wind, Mind:
Nearly 350 years after Miaoxin's death, she was remembered by the Japanese Zen Master Eihei Dogen (1200-1253) in "Raihai tokuzui," which is the 28th fascicle of his great work, Shobogenzo. Here is the story Dogen told:
Once in the late afternoon, seventeen monks traveling together from Shu came to Yangshan's monastery to seek an audience with the teacher. Miaoxin greeted them and gave them a place to stay for the night within the offices of secular affairs. They were to see Yangshan in the morning.
Not the Wind, Not the Flag:
That evening, the monks discussed how they would challenge Yangshan to test his understanding. One suggested the well-known koan sometimes called "Not the Wind, Not the Flag." Recorded as the 29th koan of the Mumonkan, this koan is about a teaching of Hui Neng, the Sixth Patriarch of Ch'an (Zen). The koan:
Two monks were arguing about a flag. One said, "The flag is moving."
The other said, "The wind is moving."
The Sixth Patriarch happened to be passing by. He told them, "Not the wind, not the flag; mind is moving."
Not Wind, Not Flag, Not Mind:
As the monks debated the koan, Miaoxin listened from another room. "How lamentable, you seventeen blind donkeys!" she said. "How many straw sandals have you wasted? The buddha dharma has not yet appeared even in your dreams!"
When the monks were told what Miaoxin had said, they went to her, bowed, and inquired about the Dharma.
Miaoxin then said, "Step forward!"
As the seventeen monks were walking toward her, Miaoxin said, it's not the wind moving, it's not the flag moving, it's not the mind moving."
All the monks realized enlightenment. They thanked Miaoxin and returned to Shu without seeing Yangshan.