Dude. Santa IS SO REAL. Can you prove that he isn't? YOU CAN'T.
Which the crux of it for me: I believe in Santa as much as I believe in other fantastical things, because I believe in believing in fantastical things, because the world is a richer place for fantastical things. So: zombies, unicorns, leprechauns, tooth fairies, Peter Pan, Tom Cruise - I choose to believe that they exist. Although it's probably only zombies I, like Jenny, would shoot in the face. Maybe also a rapid leprechaun, or a stampeding unicorn. No comment on Tom Cruise.