What did Oliver Wendell Holmes, Jr. mean by clear and present danger?

In the 1919 Supreme Court case Schenck v. United States, Justice Oliver Wendell Holmes, Jr. articulated the "clear and present danger" test to define the limits of freedom of speech under the First Amendment.

Holmes argued that while the Constitution provides stringent protection for expression, it does not protect speech that functions like force or creates immediate harm, famously noting that it would not protect a person "falsely shouting fire in a theatre and causing a panic."1

He established that speech may be prohibited if it is of such a nature and used in such circumstances that it creates a "clear and present danger" of bringing about "substantive evils" that Congress has a legitimate authority to prevent. Essentially, the test asks whether the words used are likely to result in immediate, dangerous consequences, rather than merely being offensive or urging action at an unspecified future time.21