Oh... that wasn't addressed to you... since I didn't reply to your message, but now that you did mention it...
I meant a lot of things that are proven to exist and substantiated by scientific evidence we can't really see and a lot of those evidence are circumstantial or they're just extrapolations. At the same time a lot of the things that we do see, actually our perception of those things do not correspond to reality. That's what I meant by - Seeing is not believing.
If you think that ghosts don't exist, seeing one shouldn't change your mind!