The scientific method is a way to understand everything that exists — and, if something exists, it is by definition natural. If ghosts exist, they should emit light; if telepathy is real, it should activate the parts of the brain involved in communication. If such phenomena prove to be real, then they should be classified as "natural," not "supernatural." Long before humanity learned to write, stories were told about spirits and demons and things that go bump in the night. Similar stories are told today involving religious beliefs, extrasensory perception, auras, miracles, and ghosts, just to name a few.

I’m a scientist, and therefore it should surprise no one that I am skeptical of all such beliefs. In conversations with people who embrace them, I will point to inconsistencies in their ideas, or to reasons why I don’t accept their conclusions. Often these conversations will conclude with the other person saying, “Of course you don’t believe in this. You’re a scientist. You don’t know anything about this. It’s supernatural.”
What does “supernatural” mean?

With the invocation of that word — supernatural — the look on their face often says “gotcha,” conveying that they consider the conversation over and that they have carried the day. By their understanding of the word supernatural, they have elevated their position to be beyond the scrutiny of science. They wield “supernatural” as a talisman against the baleful eye of science.

However, I have never accepted that response. The scientific method is designed to help humanity understand the phenomena found in nature and the laws that govern them. Essentially, the scientific method is a way to understand everything that exists — and, if something exists, it is by definition natural.

The Earth, the sun, the sky? They exist, and science can help us understand them. Unicorns, dragons, and pixies? They don’t exist, and they are therefore outside the realm of science. Abstract things like red and love and anger? Those things do exist, and science can study them, albeit in a way that seems indirect. For example, what we call “red” is a combination of a wavelength of light, the chemistry of photosensors in the eye, and the neurology of the brain.