Mu – "unask the question"

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https://en.wikipedia.org/wiki/Mu_%28negative%29
The Japanese and Korean term mu

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“Unasking” the question

The term is often used or translated to mean that the question itself must be “unasked”: no answer can exist in the terms provided. Zhaozhou’s answer, which literally means that dogs do not have Buddha nature, has been interpreted by Robert Pirsig and Douglas Hofstadter to mean that such categorical thinking is a delusion, that yes and no are both correct and incorrect.
In popular culture

In Robert M. Pirsig’s 1974 novel Zen and the Art of Motorcycle Maintenance, mu is translated as “no thing”, saying that it meant “unask the question”. He offered the example of a computer circuit using the binary numeral system, in effect using mu to represent high impedance:

For example, it’s stated over and over again that computer circuits exhibit only two states, a voltage for “one” and a voltage for “zero.” That’s silly! Any computer-electronics technician knows otherwise. Try to find a voltage representing one or zero when the power is off! The circuits are in a mu state.[20]

The word features prominently with a similar meaning in Douglas Hofstadter’s 1979 book, Gödel, Escher, Bach. It is used fancifully in discussions of symbolic logic, particularly Gödel’s incompleteness theorems, to indicate a question whose “answer” is to

un-ask the question,
indicate the question is fundamentally flawed, or
reject the premise that a dualistic answer can or will be given.[21]

“Mu” may be used similarly to “N/A” or “not applicable,” a term often used to indicate the question cannot be answered because the conditions of the question do not match the reality. A layperson’s example of this concept is often invoked by the loaded question “Have you stopped beating your wife?”,[22] to which “mu” would be the only respectable response.
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http://www.awakin.org/read/view.php?tid=583
The Japanese Word, Mu
–by Robert Pirsig (Oct 20, 2008)

…Mu means “no thing.” Like “quality” it points outside the process of dualistic discrimination. Mu simply says, “no class: not one, not zero, not yes, not no.” It states that the context of the question is such that a yes and a no answer is in error and should not be given. “Unask the question” is what it says.

Mu becomes appropriate when the context of the question becomes too small for the truth of the answer. When the Zen monk was asked whether a dog had Buddha nature he said “Mu,” meaning that if he answered either way he was answering incorrectly. The Buddha nature cannot be captured by yes or no questions….
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