There's a well known story that seems to have seeped deep into the modern British consciousness, about a group of men trying to understand what an elephant is like by touch alone (they are either blindfolded or blind, depending on the variant of the story). So one man has the trunk, and he declares that the elephant is like a snake. Another has the tail, and he declares the elephant is like a rope. Another has a leg, and he says the elephant is like a tree. Yet another the side, and he says the elephant is like a wall. And so on...
And that is very much like people trying to find out what God is like. We can tell something about him/her through the world she/he has made, but we also observe that other people can come to very different conclusions about God, because they look from different perspectives. But we are also fallible and some of our conclusions are wrong, just we can't tell which ones. In more mathematical language, we see that our position is essentially symmetrical to someone else's, except that we disagree on what God is like, which means that we should not be too certain about what we believe. So we look on people who are certain as being highly suspect.
But Christmas changes all of that, or it should do. Because the message we proclaim at Christmas is that the symmetry is broken. It isn't just different people coming up with different ideas about what God is like because they are coming from different places and looking at different bits of the evidence. It isn't just different groups of people each claiming that God has given them a different book. At Christmas, God himself came into the world in the person of Jesus, and showed us what he was like. So in a world of so much uncertainty, we can really know him. That's something worth getting excited about!