Yes and no -- this or that -- one or zero. On the basis of this elementary two-term discrimination, all human knowledge is built up. The demonstration of this is the computer memory which stores all its knowledge in the form of binary information. It contains ones and zeros, that's all.
Because we're unaccustomed to it, we don't usually see that there's a third possible logical term equal to yes and no which is capable of expanding our understanding in an unrecognized direction. We don't even have a term for it, so I'll have to use the Japanese mu.
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 or 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 Joshu was asked whether a dog had a 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.
That mu exists in the natural world investigated by science is evident. It's just that, as usual, we're trained not to see it by our heritage. 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. They aren't at one, they aren't at zero, they're in an indeterminate state that has no meaning in terms of ones or zeros. Readings of the voltmeter will show, in many cases, "floating ground" characteristics, in which the technician isn't reading characteristics of the computer circuits at all but characteristics of the voltmeter itself. What's happened is that the power-off condition is part of a context larger than the context in which the one zero states are considered universal. The question of one or zero has been "unasked." And there are plenty of other computer conditions besides a power-off condition in which mu answers are found because of larger contexts than the one-zero universality.
—Robert Pirsig, Zen and the Art of Motorcycle Maintenance, p. 328