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.
Many people would say things that are supernatural are just unexplained phenomena. If it can be explained, it's natural, the existence of this natural thing makes sense, does not contradict reality, and can be shown why it exists.
If it can be explained, and the existence is rational, it's natural. If it cannot be explained and it shouldn't have happened. Those are hard to come by, at least in the physical side of reality.
I do agree though, most of these things constantly associated with it (eg. ghosts, magic, demons, etc), have the potential of being understood and reasonable, we just haven't found it yet. I personally don't like to call things supernatural if they will one day be naturally explained, just not today. This understanding of 'supernatural' is more common than cats that like boxes
But I do believe there are some things that are supernatural. What I mean by supernatural, I mean, there are things that have no reason to be that way, they just are. Such as the laws of physics themselves, the fact there is something and not nothing, and the "stranger" operating this meat suit is actually yourself.
Like I said though, it's not too often to happen in physical nature. IMO, the last supernatural event might have been the big bang itself. The very instant that existence began to exist is random and has no 'why'. Thus it is supernatural. Everything after this bang is natural, as far as we know, reality is predictable to us humans. At least the materialistic part is.
The very instant of the big bang has determined that I ate reese's puff cereal. So to put that into effect. hope this made sense