the X that can be Y is not the true X
Yet another instance of
hackerdom's peculiar attraction to mystical references --- a common
humorous way of making exclusive statements about a class of
things. The template is from the "Tao te Ching": "The
Tao which can be spoken of is not the true Tao." The implication
is often that the X is a mystery accessible only to the
enlightened. See the trampoline entry for an example, and
compare has the X nature.