Innocent until proven guilty? Unreal until proven there? Something along the lines of that.
Okay, let's say, for the sake of my example, ghosts don't exist. You've never heard of them, neither have scientists. Scientists, on their own, have never discovered anything that would lead them to believe that anything supernatural exists. Therefore we continue never hearing the word "ghost". One day, some random person decides to make-up some story, about ghosts. After being passed around, scientists get word of it. They think it's absurd, because if anything is there, surely they would have found it first. Basically, people begin with the idea that nothing is there because nothing but a story says it's there in the first place. I would compare this to proving the existence of Santa Claus. Pretend for a moment you are a child. A young one, who does not yet know Santa isn't real. You can never make contact with him in any way, yet because your parents and others deceive you, you conclude that Santa is real. Is he? I'll leave you to answer that on your own, in case any little ones are reading. If Santa was created the same way ghosts were, as a story, shouldn't a sensible person come to the same conclusion in both cases?