Simply, a belief defines an idea or principle which we judge to be true. When we stop to think about it, functionally this is no small thing: lives are routinely sacrificed and saved based simply on what people believe. Yet I routinely encounter people who believe things that remain not just unproven, but which have been definitively shown to be false. In fact, I so commonly hear people profess complete certainty in the truth of ideas with insufficient evidence to support them that the alarm it used to trigger in me no longer goes off. I'll challenge a false belief when, in my judgment, it poses a risk to a patient's life or limb, but I let far more unjustified beliefs pass me by than I stop to confront. If I didn't, I wouldn't have time to talk about anything else.