We don’t know as much as we think we do, which is a problem when we are dealing with a world that is extremely complicated. We fail to draw an accurate line between what is inside and outside our heads. We affiliate with a community, share the community’s views of the world, and, because the world is too complex, we let our group do our thinking for us. But the group on which we rely probably doesn’t know any more than we do. It’s all built on a house of cards. But the fact that we feel we understand things better than we do helps to explain some of the overconfidence and extremism we see in politics.