Eugene Wigner Quote

This [gauge] invariance is, of course, an artificial one, similar to that which we could obtain by introducing into our equations the location of a ghost. The equations must then be invariant with respect to changes in the coordinate of that ghost. One does not see, in fact, what good the introduction of the coordinate of the ghost does.

Philosophical Reflections and Syntheses, On the Law of Conservation of Heavy Particles (p. 305)