The most famous Koan in the literature is Joshu’s Mu Koan. Its best known form is Case 1 of the Gateless Gate which (in the Robert Aiken translation) is:
“A monk asked Joshu “Does a dog have Buddha nature or not? “
Joshu said “Mu.”
The koan also exists in a longer form in Case 18 of the earlier Book of Serenity, which is in two parts. Two monks ask Joshu the same question.
A monk asked Joshu, “Does a dog have Buddha nature or not?”
The monk said, “Since it has, why is it then in this skin bag?”
Joshu said, “Because he knows he deliberately transgresses.”
Another Monk asked Joshu, “Does a dog have Buddha nature or not?”
Joshu said, “No.”
The monk said, “All sentient beings have Buddha nature, why does a dog not?”
Joshu said, “Because he still has karmic consciousness.”
In the Book of Serenity it’s the second question which is better known, so that’s the part which I’ll focus on.
A way of looking at these koans, which I think is a mistake, is that the teacher is wise and the student is ignorant and so they show the student being corrected by the teacher.
That perspective is very damaging for practitioners. It makes an effigy of the teachers, who become impossibly lofty, ahistorical figures, rather than flawed human beings sincerely engaged in practice.
A much better perspective is to re-see them as master and student together attempting to clarify aspects of this life.
That being said, what do we make of this koan?
First off there’s the question, “Does a dog have Buddha nature or not?”
It’s an odd question, because more than 100 years before this dialogue (if it ever was a historical dialogue) Chinese Buddhism had settled the issue of Buddha nature. There had been an argument whether all beings had Buddha nature or if some beings did not. It was resolved in favour of the more generous interpretation—that all beings had Buddha nature.
So in a way, the question is disingenuous.
Also the Chinese is terse, so it’s not clear from the Chinese if the monk is referring to an objective dog or if he’s referring to himself—does this dog have Buddha nature? The answer that Joshu gives, is either (in the Cleary translation of the Book of Serenity), ‘No’ or ‘Mu’.
‘No’ is not an accurate translation. Chinese and Japanese have three options to a question whereas we have only two. Both obviously have yes & no but they have a third option. In Chinese that third option is ‘Mu’ and in Japanese that third option is ‘hi’, as in ‘hishiryo’.
‘Mu’ is not the direct negative. It means something like —that’s not it or it’s different from that.
It tends to indicate some conceptual confusion with the question. For example if someone were to ask, “is the mountain flat?” then the answer would be ’no’ but if the question was, “is the mountain an introvert?”, the answer would be ‘Mu’ because the questioner misunderstood the nature of mountains, which don’t have psychological characteristics. Joshu’s answer of Mu to the monk’s (apparent) question indicates that there’s a conceptual confusion.
In the question, I think the monk isn’t ignorant; he’s inviting Joshu to confirm that there’s a common conceptual confusion with Buddha Nature. The question is brought out in the second half of the exchange when the monk asks his supplementary question, “.. all beings have Buddha nature, why doesn’t a dog have Buddha nature?”.
The Chinese is more terse than the translation; it’s simply ‘karmic nature.’
I think this exchange isn’t about whether the dog has karmic nature in place of Buddha nature or that the dog (or monk) has two Natures, that are somehow contesting the existential space of the dog, but rather that the phrasing of the initial question (intentionally) has an error in it.
That error is that the world is made up of dogs and human beings and walls and all the rest of it. Each of which has Buddha nature. It’s an individual quality, like height, or dog-ness.
With the Buddha Eye, all of existence is seen as a dynamic, interdependent and vivid whole.
It’s our karmic nature which splits up the world for us into dogs and human beings and so on.
The monk is intentionally asking Aunt Sally questions to clarify that Buddha nature is not a personal quality and by implication, that Enlightenment is not a personal quality either. We go astray when we take the world as it presents itself to our karmic consciousness. Or, if you prefer a more familiar language, the world as it presents itself to our socially and historically conditioned self.
We mistake those parts for reality and then attempt to impose qualities on them. Like asking how much the fat man in a dream weighs.