So many people say that they will never believe in the spiritual until they see it with their eyes, and they challenge people who believe to show them. But they never will believe it because they will always find some way to disprove it. The only way to believe is to do it yourself. No one is going to "prove" it to you, except you.
Seek out those with spiritual knowledge; learn from them. Persevere, and you will receive undeniable proof.
...but don't buy the pig in the poke, either. Until you do have the experience, neither believe nor disbelieve -- just accept what is.