"Shouting fire in a crowded theater" is a phrase often used to illustrate the limits of free speech, especially in legal contexts. It originates from a famous Supreme Court case, Schenck v. United States (1919), where Justice Oliver Wendell Holmes Jr. articulated that free speech could be restricted if it poses a clear and present danger to public safety. In this context, the phrase suggests that while individuals have the right to express their opinions, that right is not absolute.