The online science magazine,
Edge, poses a question to all manner of people and publishes their answers. This year, they asked "What do believe is true even though you cannot prove it?"
I was almost ready to say that I believe that some people are lucky, but maybe luck is just a matter of perception.
I believe that it is as important to doubt as it is to believe.
I believe that life does not have to make sense.
I believe there is no heaven (or hell).
I believe that teeth are not meant to be so pearly white.
I recommend reading some of what was written, there are some really profound and interesting commentaries (and not all science-y).