Why do you believe things when there is no evidence that they are true?

Updates
5 mo
I'm not just talking about mundane things like the mailman's came or he didn't, or things of that sort. I'm talking about really controversial, questionable things that people seem to believe in, believe in and have no doubt that they are true even when they are demonstrably untrue. A denial of what is literally in front of your eyes on a videotape. That is what I am talking about.
Why do you believe things when there is no evidence that they are true?
Post Opinion