A monk asked Zhaozhou whether a dog has buddha-nature. Zhaozhou said “Wu”, in Japanese “Mu”, no. It is the first case of the Gateless Gate, and countless students have worked with it. The answer is not a denial of the doctrine but a way of cutting through the thinking that asks.
Mu
“No”: Zhaozhou’s answer when asked whether a dog has buddha-nature, the most famous Zen kōan.