I always liked the line from "Contact" where the scientist says she's an atheist because she won't believe in anything that can't be proved. The priest asks "Did you love your father?"

"Of course I did!" (We already know that her love of her late father is vital to her.)

"Prove it."

I've long compared the religious experience to falling in love. People who haven't been in love may be dismissive and point out, perfectly rationally, that you can't prove there's anything more to it than lust turned personal. When you've been there you know there is something more to it, but you still can't prove it.

I believe in ghosts because I met one, and it near scared me crazy. I believe in gods because I met one, and She loves me. But since I can't prove that any of that happened anywhere but inside my head, I don't expect or wish to convince anyone else that it's real.