No, they can't

Your friend is likely to be a bit of a numpty

It’s fun to think up thought experiments that explain away the reasons we can’t prove they exist.

Time isn’t linear, we’re just limited to experiencing it that way while we’re alive.

After we die, we experience time differently; in an impossible-to-describe way, but is akin to a book with limitless pages. Your existence is a bookmark in this book, and dying makes you lose your place.

It is possible to re-find your place, but with unfathomable access to unfathomable histories and futures, there is a near-infinite choice of other events and timelines for a ghost to visit and observe and experience.

Coupled with that, there are laws— some sort of physical laws, not arbitrary— to visiting the pages of this book, in that they can only be done in areas that do not cause pages before or after to change dramatically. A ghost is a spec of ink on the page; it cannot write letters, words, or sentences. If anything like this were ever done, we would never know as our minds would simply accept the memory as fact without knowing, or delete the memory of a ghost the way we space out driving on a highway or having to look at our watch a second time.

Lastly, our senses are all on varying spectrums; some of us able to see, hear, smell, experience things others cannot. One of our senses is a sense of time. Some people’s sense of time operates on a scope of a wider caliber than others, experiencing things others cannot, which is why some of us may have experienced ghosts while others haven’t.

Religion tends to justify itself in the face of absolutely no evidence with "proof denies faith." It's a garbage argument, but it's accepted.

Ghosts don't have any similar excuse to fall back on when we fail to see any credible evidence whatsoever.

Is the soul a thing? Does consciousness exist as more than the sum of the electrical network of the brain? Who am "I"? These are all interesting and probably unanswerable philosophical questions. "Do ghosts exist" though, is a pretty straightforward no.

Ghosts are fun to think about and make good stories, but there's never been one bit of reliable evidence. So no it's not reasonable to believe in something that isn't real.

Nope. All "evidence" is fake. For example pretty much all UFO vids disappeared once 4k cameras got invented

Man, the downvote ratio really goes to show how many people vote without reading a post. I imagine a lot of them would agree with you, but they just saw the meme and thought, "That's stupid." Which is ironically a vote in your favor.

Can a person with reasonable beliefs have an irrational one? Certainly.

Can someone reasonably believe ghosts exist? No, it is a unreasonable belief.

For decades James Randi offered a million dollars for any evidence of supernatural shit that can be tested. Many people tried, but none were able to produce evidence to earn the money.

If ghosts were a very rare occurrence and only 0.00001% of all dead people produced ghosts we would still be completely overrun by ghosts everywhere, they would be mundane in how common they are. And that's not counting ghost animals, ghost dinosaurs, etc.

The impulse to believe in ghosts can be explained as well. For most of human evolutionary history we had predators (cats, bears, wolves, hyenas, etc). If you heard a noise in the bush and didn't assume it came from an agent you were more likely to be ambushed than if you assumed it was an agent even when it was just the wind. The survival trait biased us towards assuming agency even when it's not. When you hear a noise in your home at night your first though isn't settling foundations, it's intruder.

I'm not going to rule out the possibility of something existing that we don't know of yet.

However, if we're supposed to look for anything in any way, we first need to know what we're looking for. So, what's a ghost? Is a a soul, and if so, what's a soul?

I think that's an interesting question with or without ghost.

People who believe in souls, should attempt to explain what a soul is and how they experience their existence. Is it an emergent feature of the electrons or brainwaves that can travel in other dimensions that our normal physics can't detect or something completely unknown?

People who have experiences with ghosts and souls should be investigated. How do they detect their observations? Are they somehow able to sense things that happen in other dimensions? That'd be really cool, and I still won't rule it out. The human mind can do weird stuff. For instance echo localization like bats do, seeing more colours than normal or even just perfect pitch. Stuff like that is provable and shows that our senses can be expanded by training. Perhaps we even have dormant senses like seeing magnetic fields like birds do.

So let's say some people can see ghosts but we just can't measure it currently, because we don't know how it works. We can still make an experiment where we compare the observations from these special skills and see if they align. If it turns out that the people who can see ghosts agree, then we should definitely investigate it further and find out what happens in their heads when they see ghosts. Where does the brain impulses come from? That'll teach us about the special sense, which could then prove the existence of ghosts.

I doubt their observations match up in a controlled environment. It's a shame because it would be really easy to prove the existence of ghosts.

Real? Who cares? It's fun!

I haven't seen compelling enough evidence to believe in the supernatural.

That said, we do seem to be well on our way to engineering ghost-like phenomenon. People will set up LLMs and generative AI systems that imitate dead people, if they haven't already...

No ghosts IRL? No problem! We'll make ghosts!

Thanks Humanity. 🙄️