What do you believe in that hasnt been proven to exist?

[Excited Penguin]

The external world.  For all I know, I'm a disembodied consciousness and all the things I think I see and feel are simply a side effect of that particular state of being.  No one can prove that this isn't the case.

*shrug*  I don't find it necessary to have proof of a thing to believe that it exists.  I do, however, insist on what is called 'the reasonableness of belief', i.e. that belief is justified if such belief is more reasonable than the absence of the belief.  Thus, I believe in the external world but not Bigfoot, just as I believe in extraterrestrial life but not gods.

Boru

Even if it were "only" in your head, it would still be real. So what do your doubts consist in, exactly?