Final answer:
The clear and present danger rule helps courts determine when speech that incites or calls for action against the U.S. government can be limited under the First Amendment. Established in Schenck v. United States, speech is unprotected if it creates an immediate threat and leads to substantial evils that Congress aims to prevent.
Step-by-step explanation:
The clear and present danger rule is a legal doctrine used by courts to decide whether speech is considered seditious and whether it could be limited under the First Amendment of the U.S. Constitution. This rule was established in the landmark decision of Schenck v. United States in 1919.
For instance, under this doctrine, advocating abstractly for the overthrow of the government is usually protected as free speech; however, if someone calls for imminent violence or a direct action against the government that creates a clear and immediate danger, such speech can be subject to limitations.