Well, how do I define something that is so instilled in our beings since day 1...
Commonly, the term is used interchangeably with 'faith' - be it in religious or spiritual sense. But the term has quite a lot of versatility to it, given that our conditioning and beliefs are often held so deeply and with such conviction. I think it's fascinating that we were given this as a working concept for the medium of documentary, seeing as the crux of the medium operates upon being able to uncover the truth, or what to believe, per se.
But belief can be any number of things. Courage, committment, certainty, throwing caution to the wind... and what about disbelief? Isn't that too a belief in itself? I guess the real difference is that belief is generally given a positive connotation, and rightfully so. So many people have fought for what they believe in, and for that I admire their steadfastness. Belief, to me, is inherently stubborn, but nonetheless, a necessity - for what kind of world would we live in if it were devoid of any of these things? Would the world even exist for us?
There's an idea worth pondering.