One night I saw a ghost.

I toss and turn a lot when I'm sleeping. A few months ago, I turned onto my left side and I briefly opened my eyes. The room was dark except for a dim light from the closet. It was probably somewhere around 4AM. I saw movement out of the corner of my eye, both eyes widened, and I saw the silhouette of my wife walking towards our master bathroom. As she passed in front of me, I saw her skin and her hair. She stopped in the doorway and stood still, lingering just long enough to activate my uncanny valley response. There was no reason for her to stop and linger like that.

Then, she began walking again. Normally, this would be where she walks in, closes the door behind her, and I see the crack at the bottom of the door glow yellow as she flips on the light switch. That didn't happen. Instead, after three of four steps into the bathroom, she evaporated into thin air. Then, I quickly turned over and saw her still laying in bed next to me.

It was a jarring experience. I've never really hallucinated before; certainly not a fully formed human being with the same features and gait as my wife. Maybe a spider on the wall here or there as I'm falling asleep, sure, but never a fully formed apparition.

I'm quite skeptical, so I don't think it was an actual ghost. It was likely just the remnants of my REM cycle spinning down more slowly than it should have. But even though it wasn't a supernatural event, it was incredibly strange and I can now definitely understand how some people can convince themselves, and others, that they've seen something supernatural.

After all, people with schizophrenia experience things like this all of the time. The building blocks are sitting there in our brains, dormant for most.

Was it just a double exposed memory?

My main takeaway from the encounter was that my brain can apparently project perfect illusions into four dimensional space that I cannot discern from reality, and then it can take them away. Of course, I knew the human brain had this power prior to experiencing it first hand, but it did actually make a big difference to be tricked by it in real time.

What's to stop the rest of reality from evaporating, too? If I suddenly lost all of my senses, would I experience the same hallucination in the same way, and at the same time?

She walked around our bed — her lower half wasn't visible at all until she rounded the corner — and then into a doorway, and then into the bathroom. The hallucination was interacting with the objects in my field of view. The hallucination obeyed the laws of physics. Her hair was swaying with her movement — the hallucinated hair had mass and was affected by gravity.

Was I hallucinating the scene as well, or just the figure?

What if I suddenly lost all of my senses while this scene was playing out? What would happen to the hallucination? Would my ghost wife's entire body appear because my bed — in my real bedroom — was blocking my view of her? Would she even still be walking? Would she stop and stand in place if I could no longer see a doorway that she could walk into?

If the hallucination was simply the projection of a memory into four dimensional space, then even if I lost my senses, nothing would change. The memory was a snapshot that was already taken. Even if the entire layout of our master bedroom changed right after I lost all of my senses, then I suspect that I would experience the exact same hallucination. If... it was fully a memory.

I was laying on my side. So, if it was a memory, my view of reality was 90 degrees different than it would be if I were standing. The memory must have been a snapshot from that exact spot that I was laying in. But if that's true, when the ghost evaporated into thin air, why was the bathroom door in the exact same position? In fact, nothing in the room was different when the hallcuination faded and I fully stirred awake. It was a perfect transition from the hallucination back into my waking reality.

If my hallucination was a memory, then the setting — my master bedroom — must have been the real time scene's backdrop that my eyes were processing. Then the figure — my wife — must have been a projection of a memory, but with background keyed out and replaced with my waking reality. A kind of double exposure.

But what about the variables?

I sleep with a fan on. I can't sleep without the white noise and I feel uncomfortable if the air in the bedroom is too still. In my memory of this hallucination, her hair wasn't really moving that much other than with the sway of her hips as she walked. It was being tugged down by gravity, but I can't remember if the fan was hitting her hair.

If her individual strands of hair were interacting with the air current, then her projected form couldn't have been a memory. The movement of the air, and how it interacts with invididual strands of hair, would be too variable to be written into a perfect memory.

I just can't remember if the ends of her hair were dancing in the wind or not. If they were, then that would open up an entirely new can of worms... which sounds fun, so let's say that the ends of her hair were twisting in the wind of my fan.

Is it all just static?

If her hair was moving, then it wasn't just a double exposed memory of my wife creeping across reality: it was a projection. But from what? It couldn't have been my own brain creating the projection, could it? To create that figure and place it into reality, my brain would have to process all of the physics itself. Billions — trillions? — of moving atoms. It would have to calculate and recalculate, redraw, each frame as the variables in the room shifted. It would have to create the sound of my fan. It would have to obey time.

When I hallucinate, is my brain recreating time, too? The ghost. My fan. When the ghost walked, she didn't look any slower or faster than she should have. Her steps looks exactly as they should have. The whir of the fan sounded exactly how it always has. Was I hearing the fan as it spun in reality, or was I hearing my brain's perfect recreation of my fan?

There was a light coming from our closet and dimly lighting the room. Was my brain creating that light and the speed it was traveling at? The ghost was lit exactly how she should have been.

It doesn't make sense and it seems inefficient. Can a hallucination be an ad-hoc creation of my brain? It can't know all of the physics, can it? How light interacts with the environment, the vibrations of sound, and how that interacts with time. Wouldn't it have to be a projection of moving images?

Do I have an inherent sense of reality? Are the rules of physics hard-coded into my brain somewhere so that it can create hallucinations that interact with the real environment if it needs to? What would be the point of that?

All the world is a stage.

It seems more plausible that my brain is just interpreting the signals of projections from an external source. All of the work is being done externally and instead of my brain filling my field of view with projections itself, my field of view is actually a cacophony of signals being interpreted by my brain and organized into reality.

That reality is the stage, the lighting, the cameras — and my brain is the television. It can only interpret the radio waves over the air, and but it can't change them.

Perhaps my hallucination was like a CCTV feed that only I could see, and it was briefly overpowering the signal from outer reality — the one we all share. Perhaps it was a previous broadcast stored in my memory, being rerun as I was sleeping? Was one part of my brain replaying the broadcast while another part was waking me up — were they out of sync? Maybe what I saw was supposed to be a dream.

And when that rebroadcast ended shortly after I woke up, my brain picked up the signal from our shared reality again, dropping me right back into this plain and boring world. Like a wave lapping onto shore, and back out again; the sand went frothy briefly, but then as the water absorbed back into it, everything looked as it had before — everything in its right place.

So where's the broadcast coming from?

Seeing a ghost made me question reality directly. I had thought about the possibility that we live in a simulation before, but after seeing the ghost and thinking through all that actually entails, I am more convinced than I have ever been that I am living in a computer program.

Does that matter? Not really. This is still my reality. My views about religion haven't changed. My outlook on life hasn't changed. I was the same person after she evaporated into thin air that I was before.

It doesn't make me question who I am, but it does make me question who you are more than I ever have. It's plausible that you don't exist, reader. I still don't believe in ghosts, but now I do believe that I can be fooled whenever my brain is properly motivated to do so. That's a little scary, but I guess it's no scarier than anything else that can crumble in front of me at a moments' notice.

I'm just glad the ghost didn't talk to me. As it stands, all I saw was a little movie play out. I'm glad I didn't tell the ghost that I loved her as she walked by. Imagine if she looked at me and said, "I love you, too."

The fourth wall remaining in tact is safer for my overall sanity. In fact, that fourth wall is probably the difference between sanity and insanity, and I got a little too close for comfort. I also feel much more sympathy for people forced to see or hear hallucinations all day. It's not fun to question what is and isn't real, if even for a moment.