About ten minutes ago, my 4-year old son was afraid to go in his room because the light was off. "There are ghosts in there!" he said. "I think ghosts are real!"
I went in and turned on the light, and asked him why he believes ghosts are real. He said that one time, one of his toys fell off a shelf, and no one pushed it. It fell by itself, and that's why ghosts are real.
I explained that sometimes when you put toys on a shelf, they might stay there for a while, but if they're not secure, they might fall off by themselves. This doesn't mean ghosts aren't real, but I didn't think it had to be a ghost just because the toy fell by itself. Sometimes that just happens.
My 6-year old daughter walked in the room and joined us. My son continued, "But Dad, Berlin [the neighbor girl] said she thinks ghosts are real!" My daughter nodded her head, confirming the story.
"Well, you shouldn't believe something just because someone else believes it," I said. "You get to decide for yourself what you believe. I don't believe ghosts are real, but that doesn't mean you have to believe that, either. It's up to you to decide."
"Do you know how I decide what I believe?" I asked. They shook their heads. "I see if I can figure out what's really happening. And if I find an idea that explains everything I can see happening, then I tend to believe it. If I don't see any reason to believe something is really happening, then I don't tend to believe it."
Then my daughter said something that totally took me by surprise. "I don't know yet if I believe in ghosts or not." That was an excellent answer, and I told her so. My son wasn't convinced though. He still believes in ghosts, and that's okay.