"To promote the improvement of Society it is essential that Mind should be free. Unless individuals are permitted to reflect and communicate their sentiments upon every topic, it is impossible that they should progress in knowledge."
- Tunis Wortman, 1800.⁸⁸

"The question in every case is whether the words used are used in such circumstances and are of such a nature as to create a clear and present danger that they will bring about the substantive evils that Congress has a right to prevent. It is a question of proximity and degree."
- Justice Oliver Wendell Holmes, Jr., in Schenck v. United States, 1919.⁸⁹

"Utterances inciting to the overthrow of organized government by unlawful means . . . by their very nature, involve danger to the public peace and to the security of the State. . . . A single revolutionary spark may kindle a fire that, smouldering for a time, may burst into a sweeping and destructive conflagration."
- Justice Edward Terry Sanford in Gitlow v. New York, 1925.⁹⁰

"A function of free speech under our system of government is to invite dispute. It may indeed best serve its high purpose when it induces a condition of unrest, creates dissatisfaction with conditions as they are, or even stirs people to anger."
- Justice William Douglas, in Terminiello v. City of Chicago, 1949.⁹¹

"It can hardly be argued that either students or teachers shed their constitutional rights to freedom of speech or expression at the schoolhouse gate."
- Justice Abe Fortas, in Tinker v. Des Moines, 1969.⁹²

"If the time has come when pupils of state-supported schools . . .can defy and flout orders of school officials to keep their minds on their own schoolwork, it is the beginning of a new revolutionary era of permissiveness in this country fostered by the judiciary."
- Justice Hugo Black in Tinker v. Des Moines, 1969.⁹³