While I was preparing my report on the El Chupacabra phenomenon for The Amazing Adventure 4, it became clear that people were interpreting all manner of unexplained animal activity as the work of the legendary goat sucker. 100 years ago, this wouldn’t have been possible. Why? Because 100 years ago, El Chupacabra didn’t exist as an idea. No one could have believed in it because no one had thought of it yet.

“Seeing is believing” is an old expression, and one could argue that it’s the basis of skepticism. It translates to “I’ll believe it when I have evidence for it.” But evaluating that evidence is actually quite tricky. In fact, the reciprocal expression is also true: believing is seeing.

An example I often give is the “noise in the basement.” You’re home alone and the power goes out. The fuse box is in the basement, and you decide to tip-toe down the rickety stairs. Of course you can’t find your flashlight, so you’re using your iPhone to light your way. You see the fuse box behind a stack of old boxes, and you curse yourself for not anticipating the need for a clear path.

You may feel nervous and uneasy. Why? Because many thousands of years of evolution have conditioned you to believe you’re in a very dangerous situation. You’re vulnerable to attack by lion, hyena, cave bear, tiger, or any number of other real-world threats that your ancestors actually had to worry about.

Of course, you’re not in the veldt. You’re in a suburban basement, where the most dangerous creature you’re like to encounter is a brown recluse spider, or perhaps another human.

You move the boxes, open the fuse box, and try to figure out which fuse to replace. Suddenly, you hear a noise behind you. You stiffen, you feel the adrenaline enter your bloodstream, and you wait to hear more. You do... it’s a distinct scuffling coming from directly behind you.

Believing you’re in real danger, you whirl about, and catch something moving behind the water heater. YOU ARE NOT ALONE. Something is in there with you!

You bolt up the stairs, shut the door, and just as you’re about to leave the house, the lights come back on. It turns out it wasn’t a fuse anyway (and you should have looked out the window at all the other dark houses to realize that.)

What did you see?

It really depends on what you were thinking at the time. If you had just watched War of the Worlds, you could easily believe it was a Martian. If the house was old and had a gruesome history, ghosts might leap to mind. And if you lived in Puerto Rico and some of your chickens had been found dead recently, you might blame El Chupacabra as is the fashion today.

You can tell your friends that not only do you believe in these things, but that you saw one. And after all, seeing is believing.

Remove the context though, and what do you have? Pure evidence. There was a scuffling sound, and you detected movement. That’s it. That’s all you have to go on. What could it have been?

It could have been many things, and the only thing you can say with any certainty is that you heard something and saw something move. Except that even those things aren’t certain… you were full of adrenaline, and hyper-sensitive to any stimulus. You could have imagined the noise, and the movement could have simply been the shadow shimmer caused by your light’s sudden movement.

Boring? Maybe. It would be exciting to tell your friends you’d seen a ghost, and that’s why, I think, people are so persistent in their belief despite evidence to the contrary. If the next day they enter the basement and find a hole in the window screen, and raccoon prints outside, that makes for a far less interesting story, which in turns makes them far less interesting people (at least in their minds.) And after all, just because it’s likely that raccoons had entered your house doesn’t mean that there aren’t also ghosts in there as well. It’s just a question of which is more likely.

So again, I ask… how can you tell the difference between a ghost and an alien? On all those “Ghost Hunting” shows, they are, well, hunting ghosts. If they actually find something, they automatically call it a “ghost.” How can they know it’s not an alien? I've yet to hear a decent answer for that.  Or how about a gnome? Or a kobold? Why isn’t there a “Gremlin Hunters” show, or an “Elvin Infestations” special? The answer is that those memes are no longer part of our consciousness. They’re considered fairytales now, and I wonder why ghosts haven’t made that transition yet.

As thinking humans, we can do better than this, and our way of doing better is called science. This is a process by which we remove bias (to the greatest extent possible), and consider just the evidence on its own merits. Why do we do this? Because thus far, it’s the best way to gain knowledge of our world. Direct experience is compelling, but it’s not actually accurate, and a little critical thinking can go a long way to correcting our mistaken assumptions.

I’m still going to jump if someone yells BOO! in the dark though.