The only thing I really have to say about the significance of dreams is that you can't believe in it without having to take on some piggybacking beliefs that might not seem so plausible.
For instance, if a deceased loved one, or any kind of spirit, is able to visit you in a dream, that means that the dream environment actually has to be a place. For you to meet someone there, there has to be a "there" in the first place, where you are at, and where they can go. So the assumption is that, every night, during REM sleep, we have some kind of out-of-body experience, and we travel to another environment, and then wake up to remember that as a dream.
If you are someone who remembers a moderate amount of your dreams, this may be hard to swallow. Let me give you an example from my own experience.
I was in my bedroom, but it actually looked like no room that I recognized during waking. There was something trying to get in through the doors, and the windows. At the same time, though, I was in a town in the game Black and White 2, and the spots where my door and window were in my bedroom were the gates to my town, and there were boulders rolling down hills, trying to break through the gates. These two points of view, seemingly interchangeable, switched back and forth throughout the course of the dream, me being in my room one minute, and being a giant presence in the middle of my town the next.
And, for me to believe that another consciousness could visit me in the middle of all that mess, I have to believe that it was really happening. And this dream is a mild example. Some dreams are so abstract, and make so little sense to the waking mind, that it is very hard to believe that somewhere, these images were actually formed out of some kind of material.
And we can't stop there. If dreams are real things, happening in real places, then what of hypnagogic imagery? The limitlessly bizarre things that we see in our eyelids as we drift off at night? I've made a game of describing these to my significant other. "Looks like... the inside of a throat, with a thousand dice spinning around it, and a tunnel in the middle..."
And if it seems obvious to anyone that hypnagogic imagery is just a product of the mind, it seems obvious to me that dreams are, as well as lucid dreams, and dissociative experiences. I also don't think it's farfetched that we could dream about meeting someone that we miss very much. I've had plenty of dreams about people who are still alive, not all of them flattering.
It might just be a matter of what's comfortable compared to what's true, and I don't have the authority to tell you which is more important. I'm not a truth purist, it's just an interest of mine. It's not my place to take away anyone's significant experience.
But if you are interested in the truth, then you have to accept that dreams being contained within the skull is definitely a likely possibility. As I see it, that's an explanation that isn't broke, and I have no interest in fixing it.
Thanks for reading.