I regularly find it utterly bewildering, dismaying, and depressing that the majority of the world seems to believe in ghosts, spirits, and anything else that would fall under the umbrella of the "supernatural" or "paranormal". I certainly do not, because I don't believe in anything on insufficient evidence, and neither should you. Incidentally, this goes for things like astrology and psychics as well. I was tempted to write a separate piece on this, but I don't think there's enough material there to warrant it, so I'll throw it in here. Astrology, psychics, healing crystals, and anything else of that nature is completely false, unsupported by evidence, and one would be wise to be extremely skeptical of any such thing that is clearly a business designed to make money.
My mind is, in principle, open, but there's simply no reason to believe in the so-called "supernatural". My beliefs would adjust accordingly if there was substantial evidence of ghosts that occupied a respectable place in our academic discourse. Instead, ghosts are exiled to the same place as UFO encounters and alien abduction. Every ghost encounter is either fake, uncorroborated hearsay, a misinterpretation of explainable, rational events, or a hallucination. It's worth noting that experiencing a hallucination is fairly common, and does not mean that a person is crazy. It can happen for all sorts of reasons. The brain is powerful enough to make us see or hear anything that isn't there, and vice versa: it can prevent us from seeing or hearing what is there. For most part, our brains show us what is really there, and only what is really there, because that's what they've evolved to do. It's their job, and they are pretty good at it, most of the time. They won't falter in their job for no reason. But the brain's ability to show us an accurate reality can become surprisingly tenuous more often than you might think.
Incidentally, it's worth noting that our brains our often much less reliable than we think. Our perceptions and memories are faulty, and most of what we experience is a reconstruction based on what we expect reality to be. For instance, visual information that we take in passes through our memories, and our memories actually change what we see based on our expectations. If we see a tiger, for example, the image will pass through our memories and essentially be cross-referenced with what we know about tigers. Our brain will then decide what a tiger is supposed to look like based on our memories, and the image we see will actually be reconstructed and altered by our brains to fit. For more on this, check out Steven Novella's Your Deceptive Mind.
The unreliable nature of our minds readily explains why so many people think they experience confirmation of the so-called "supernatural". People often see what they want to see, or what they expect to see. If one believes in ghosts, and they see some wisp of fog, their brain may actually alter the image to show them a ghost based on what they think a ghost looks like. The same type of thing goes for hearing as well. This is not the same thing as a hallucination, either. This is trickery of our brains as they piece together what they perceive in an attempt to show us what is real, a process which doesn't always work perfectly. Rampant confirmation bias, wishful thinking, and sensory deception keep humanity stuck in a loop of gullibility and superstition. Consider this: if you think you saw or experienced the presence of a ghost, which is more likely--that you had a close encounter with something for which there is absolutely no solid evidence, or that you were mistaken?
People don't like to hear this, but humans are basically masters of self-delusion and self-deception, and our perceptions, memories, and what we think we know and experience is extremely fickle and easy to fool in many ways, which is why people's personal experiences are wildly unreliable. Arguments like "I know what I saw," or "I know what I heard," are often fairly useless. Nobody wants to believe that they can be mistaken about what feel like vivid experience, but we can be. That's why we need the scientific method. We need repeated experimentation, reliably duplicated results, and hard evidence. One of the first rules of good science is not to trust your eyes, your feelings, or your intuitions, but trust the tools, the measurements, and the calculations. I believe that if ghosts or things of that nature were real, we would have much better evidence at this point that occupies a respectable place in our scientific discourse. Instead, all we have are essentially people's personal testimonials, of which I remain extremely skeptical.
My biggest question regarding something like ghosts is this: if they did exist, then why would they intentionally keep themselves exiled to that spooky, mythical, pseudo-science corner of our world? What would they have to gain by doing this? Why would their only means of interacting with us be creepy haunting tactics? If ghosts did exist, it seems more likely to me that they would be like Obi-Wan in Return of the Jedi. Answers such as "they don't have enough energy or strength to fully appear in broad daylight" seem a complete cop-out. The real answer is much simpler and more reasonable: people like ghost stories. They're fun. Spooky stuff is fun. Halloween is fun. Unexplained phenomena are interesting. People want to live in a world full of mystery, and feel it gives life more meaning. My answer to this is exactly the same as those I've provided in the many criticisms of religion that I've written: we need not believe anything on insufficient evidence to lead fulfilling lives full of romance, mystery, awe, wonder, profundity, and even spirituality. The greatest, most wonderful, and most terrifying mysteries of all time are all around us, and have nothing to do with pseudo-science or grainy, low-rez, shaky cam videos of spooky eyes and disembodied figures lurking in the catacombs of the ancient world.
But I believe that the more important, and more interesting question is what we actually mean by "supernatural". The word literally just means "beyond natural", as indicated by the prefix "super" which means of the highest degree. I submit that the so-called "supernatural" cannot exist because the very concept is impossible, flawed, and oxymoronic. No matter what exists, it would be a part of nature, because nature encompasses everything that is, and therefore nothing would be beyond it. People tend to have this idea in their heads in that the natural world denotes plants, animals, and rocks, and anything else is either unnatural or supernatural. However, nature simple refers to anything that exists outside of human activities or intervention. It's the opposite of artificial. This encompasses everything in the cosmos that we didn't create. Therefore, anything that exists independently of us would do so naturally, and would simply be a part of nature.
Let's suppose that, for argument's sake, every spooky thing that has ever been believed by humans is literally real. Ghosts, gods, demons, heaven, and hell. All of it. There's no evidence of any of it, of course, but just go with me on this. If these things existed, then they would simply exist as a part of all of existence, making them a part of nature. Many people like to say that supernatural or divine things exist "outside of space and time". This cute explanation is devoid of any meaning or substance, and does nothing to counter my argument. Alright--say it is outside of what we perceive as "our space", or even our timeline. So what? Why would that mean that that "otherworldly" place isn't still a part of nature? The natural world wouldn't just encompass our planet or even our universe. It would encompass anything that exists independently of us. This means it would encompass the entire multiverse, if there is such a thing, complete with any dimensions that may exist. There's no reason to say that any of it is "beyond nature".
We usually ascribe the moniker of "supernatural" or "paranormal" to things that we can't explain, but a current lack of an explanation obviously doesn't mean there isn't one. It just means we haven't found it yet. If "paranormal" simply means the unexplained, then I certainly believe in the paranormal. Of course I believe that there are things we can't explain, but that doesn't mean that there isn't an explanation, whether we will ever get it in hand or not. (It might be useful for me to mention that I believe in UFOs in the same way; i.e. I believe that there have been many flying objects that were unidentified, but I just don't think that there's any good reason to believe that any are aliens.) Many things we understand today, such as electromagnetic waves, would have been thought to be supernatural magic not that long ago. Let's take the example of ghosts. There's no good evidence of them, but let's suppose that there was. If ghosts were real, then they would simply exist as a part of nature that we can't yet explain or understand. Perhaps they are made of pure energy, or plasma, or some kind of matter that we don't yet know about that passes through solid matter. Whatever the case, and regardless of whether they exist inside of us, or are the embodiment of a deceased person, once the explanation was found, a ghost would simply be regarded as yet another naturally occurring phenomenon, like electromagnetic waves, black holes, or any number of other incredible phenomena. They would simply be--they would exist as anything else in nature exists. If they could travel between dimensions, then that would simply be another aspect to their existence--something else that we can't yet explain. Whatever the explanation, whether we ever found it or not, there's simply justification for calling it "supernatural". The term "supernatural" often seems to describe things that we think shouldn't, don't, or can't exist, but seem to anyway. This is just lazy thinking. If something exists, then it obviously can and does, which means it's not impossible, which means there's no reason to file it into this category of impossibility. Something being unexplained doesn't render it magical or spooky.
Making a detour into religion, this same logic applies to the concept of divinity or holiness as well. What does it mean for something to be "divine" or "holy"? Insofar as I understand it, these terms mean that something either pertains to a god, or was touched by a god, or something of that fashion. Why would that make something "holy", though? What does "holy" even mean, really? I would argue that if a god or gods did exist, they too would simply exist as anything else in the natural world does. They too would simply be a part of nature--a part of the cosmos that we can't yet explain, and wouldn't warrant the label of "supernatural" or "divine". If there was a god, what reason would there be to think that he/she/it wouldn't simply be a being like any other, just one of greater power and/or intelligence, and one who's existence we cannot yet explain? What reason would there be to assume that that being, and anything it touched, would inherently be holy? The entire concept of holiness seems to me to be an empty and meaningless one.
Likewise, the concept of "supernatural" is also hollow. There's simply no need for it. Anything that exists simply exists, whatever and however that may be. I find it curious that many people seem to want to live in a world where spooky things that are "not of this world" exist. I believe that this way of thinking about the so-called "supernatural" isn't useful. There are so many things that would have been thought of a supernatural at one time, but as we explained them, now they're just natural, and there's nothing spooky about them. I think that as each phenomenon is discovered and explained, they just come to be thought of as part of the natural world, one by one, and the realm of the supernatural continues to shrink. There are only two categories of things in all of existence: those we can and have explained, and those we haven't. The category for things that exist outside of nature serves no purpose.