"Mu becomes appropriate when the context of the question becomes too small for the truth of the answer
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 curcuits are in a mu state. They aren't at one, they aren't at zero, they're at an indeterminate state that has no meaning in terms of ones and zeros."
Robert M. Pirsig Zen and the Art of Motorcycle Maintenance