Originally Posted by
DarkDwarf 
Everything is not a belief, but everything is untrue. A chair is a chair, but the idea that the chair is there could be untrue.
Or the fact that it is even a chair (a society who has never seen a chair might view it differently). True or 'not true' are human constructs driven entirely by context. The idea you are trying to describe is one of perception. Everything comes down to perception and, perhaps more importantly, when.