Welcome to a possible new series. Since I started the Doggerel series with "Supernatural," it seems appropriate to start this series on a similar note. While Doggerel deals with cliches skeptics like me are sick of dealing with, this series will deal with unstated assumptions that probably need more exposure.
Today's entry is "I Know What's Supernatural." The unstated assumption: That there's some unifying, identifiable quality possessed by supernatural things and/or natural things that separate them.
But what is this quality? It's not invisibility, because that'd make most of the electromagnetic spectrum supernatural, as well as even more boring things like air. For much the same reason, it's not stuff beyond our senses. There's no reason why our having particular sets of senses would define something's nature.
Instead, I'd say the barrier between the "natural" and "supernatural" is an arbitrary construct of our culture and level of familiarity. Take any electronic gizmo far enough back in time, and it'll be regarded as magical by the locals. Heck, many of our ancestors thought lightning was supernatural, but we do not. Why's that? Because we as a civilization, if not as individuals, understand how lightning works and what it is. That understanding dragged lightning down from the mystical mumbo-jumbo the priests attached to it, and put it firmly in the natural world.
There is no objective difference between "natural" and "supernatural" that would merit treating them differently. We've gained great understanding of our world and are continuing to learn through methodological naturalism, where we treat everything with an effect on the world the same way.
If I'm wrong, tell me: How can you know if something's "supernatural"?