I've been thinking about this a lot lately. Whether we mean 'supernatural' in terms of religious miracles, or whether we mean it in terms of ghosts or other such events, I posit that the concept of the supernatural cannot exist.
Conjecture:
Anything with the label 'supernatural' which is found to be a real part of the physical world (let us say someone proves ghosts exist), then whatever is behind that must be underpinned by a scientific principle and must, therefore, be a natural occurrence (assuming that no technology is the cause).
Anything natural cannot be supernatural, and anything supernatural which is proveable is, by default, natural, meaning that the concept fo the supernatural cannot exist.
Discuss.