Ok, here's what i think:
When a person is born (maybe not everybody), restrictions are placed upon that person. They are told they can't do this, they can't do that. Children are told there's no such things as ghosts, and we all know that children are very impressionable. This is the reason children are the ones who report knowing things from past lives, being able to see things adults can't. It's those restrictions that are placed on them that results in the loss of those things.
Now, to be able ot believe in astral projection, summoning spirits from other realms, spirit guides etc. a person usually needs to break down some of those walls (restrictions) that have been built in their way. I mean, people don't just get up one morning and say "I feel like getting into the occult. I think i'll draw a magic circle and summon up Satan after breakfast." They first have to break through that wall that was put there by people saying it's not possible.
So why stop at summoning spirits, or astral work, or anything like that? Why build more walls by saying things aren't possible? Nobody knows just how much we can do with our mind in... wherever we are, so why assume to know?
Nobody knows something is impossible until they've done it [
I'm not saying people are going to be able to do these things in this life-time or maybe ever, all i'm saying is that i believe it's possible because i don't want to have those walls in my way.
Sorry if that was un-necessarily long.