Well, how can one not assume that things are how we think they are? Because even once we change how we think about things, we are still stuck with how we think about things. We can't think about things we can't think about. It's impossible to believe something you don't believe.

Even the thought, "things might match up our beliefs" is still a belief. So, once you think that thought, it is a belief, so things not matching up with your beliefs is actually things matching up with your beliefs, because your belief is that things don't match up with your beliefs.