The Zen Concept of Emptiness, or Mu

A monk asked, “Does a dog have a Buddha-nature or not?”
The master said, “Not [Mu]!”
The monk said, “Above to all the Buddhas, below to the crawling bugs, all have Buddha-nature. Why is it that the dog has not?”
The master said, “Because he has the nature of karmic delusions”.
—The Recorded Sayings of Zen Master Joshu, koan 132, translation by James Green


Mu is a term in Zen that is used to describe “emptiness ” or “nothingness”. This is what a zen practitioner hopes to attain and realize. The universe is in a constant flux of change. Nothing ever remains unchanged. As long as we continue to desire we will always be suffering. If one wishes not to suffer, desire must be cut-off from one’s life. Physically, all sentient being suffer with birth, illness, old age, and death. The whole body-mind complex is in a state of suffering. The third salient mark below suggest that at the core there is a void. If indeed we are composed of the five skandhas we will find that within or behind any of these elements no ego-entity will be found. The fourth mark suggest that we are mu. Since everything depends on other factors to exist, all is without a core or substantial reality. The term mu gives this explanation a name.

I. An individual is composed of five skandhas:
D.volitional formations

II.The buddha taught that all phenomena are branded with four salient marks:
A.impermanence (anitaya)
B.suffering (duhkha)
D.emptiness (sunyata)

A monk asked Zhaozhou Congshen, a Chinese Zen master (known as Jōshū in Japanese), “Has a dog Buddha-nature or not?”
Zhaozhou answered, “Wú” (in Japanese, Mu)
—The Gateless Gate, koan 1, translation by Robert Aitken

Mu is like a circle of light one sees in a dark room. To our surprise, we learn that the circle was a reality brought about because there was a little boy in the room twirling a stick of burning incense in the dark room. The circle was merely an illusion created in the mind, phenomena is just this way. It depends on certain set of causes and conditions to exist or seem to exist. We are no exception to these principles. “form is emptiness” What we find at the heart of all things is void. Our basic components are the same. What makes me and you may be the same but what you are and what I am is composed of different conditions. Each of us once again become responsible for our own actions.
Mu needs to be realized at every moment of our lives. The intellect will understand mu but it must be known that mu is reality. The last step we can take after these realizations is to realize that things are what they are. This step is termed the Middle Way (Jap: Chudo). It is a complex realization brought about through deep thought process. It is described in the chapter as thus: “truly non-existent but mysteriously existent.” The Middle Way teaches us to avoid extremes. It brings practicality back into the life of the practitioner. The middle Way bring harmony back into our lives.

“Before a man studies Zen, a mountain is a mountain
after he gets insights, a mountain is not a mountain
When he really understands, a mountain is a mountain”

Zen teaches that the source of all suffering stem from desires. It is interesting to think that Zen even preaches that suffering can even arise when one even desires nothingness. Non- attachment to any of it is the ultimate. To be attached to nothingness can lead one to detachment. Wisdom must encompass compassion. Action must be effortless the Tao Te Ching says it like this “He does nothing, but there is nothing he does not do.”

Mu (negative)