At the end of the classic independent film Reservoir Dogs, the characters end up in a Mexican standoff. The criminal gang’s ringleader, Joe, insists that Mr. Orange is working with the police, even though he is dying on the floor, having been shot during a failed jewelry store heist. Mr. White – the crooks use aliases – insists that Joe is wrong. Guns get drawn. Mr. White demands some proof for Joe’s claim about Mr. Orange. Joe angrily responds, “You don’t need proof when you have instinct!” You can watch the (admittedly brutal) scene here.
This illustrates something we all experience: People disagree about many things for many reasons. Sometimes they have different sources of information. Often, they have different intuitions about shared information. Sometimes, their views are clouded by self-interest. And, frequently, people disagree because a pattern of facts matches their experience, even though they do not have rigorous proof.