The Non-expressible Truth

When Nansen visited Hyakujo, Hyakujo asked him, "Is there any teaching left that all the sages of old have not explained to people?" Nansen replied, "There is." Hyakujo said, "What is it?" Nansen said, "Not mind, not Buddha, not things.' Hyakujo then said, "Has your exposition ended?" "Yes," said Nansen, "what is yours?" Hyakujo replied, "I am neither sage nor saint; how can I express what has never been expressed?" Nansen said, "I cannot either." Hyakujo concluded, "For your sake I have finished my exposition and with good results!"

"Not mind, not Buddha, not things" is the essence of this koan. All things are continually changing, is Nansen's inexpressible truth. But the one who says he knows, does not really know; the one who says that he does not know, is the one who really knows.