We like to think of ourselves as rational beings who arrive at beliefs by weighing evidence. That is a comforting story. And like most comforting stories, it is largely false. In practice, human beings are far more tribal than rational. We do not simply ask, What is true? We ask, usually without admitting it, Who is saying this? Whose side is this on? Will agreeing with this strengthen or weaken my standing? Belief is often less a matter of reason than of belonging.