“Those are twelve reasonable men in everyday life, Tom’s jury, but you saw something come between them and reason. You saw the same thing that night in front of the jail. When that crew went away, they didn’t go as reasonable men, they went because we were there. There’s something in our world that makes men lose their heads – they couldn’t be fair if they tried.”

– Harper Lee

To Kill a Mockingbird, Chapter 23. Atticus is talking to his son Jem about the mob mentality, explaining how reasonable individuals can lose their reason and humanity when they act together as a group. Examples being the mob that planned to lynch Tom Robinson and the jury that convicted him.