  We give a general overview of various flavors of the equivalence principle in
classical and quantum physics, with special emphasis on the so-called weak
equivalence principle, and contrast its validity in mechanics versus field
theory. We also discuss its generalisation to a theory of quantum gravity. Our
analysis suggests that only the strong equivalence principle can be considered
fundamental enough to be generalised to a quantum gravity context, since all
other flavors of equivalence principle hold only approximately already at the
classical level.
