“Freedom of speech is a principal pillar of a free government; when this support is taken away, the constitution of a free society is dissolved, and tyranny is erected on its ruins. Republics and limited monarchies derive their strength and vigor from a popular examination into the action of the magistrates.”

1770s, A Summary View of the Rights of British America (1774)

Charles Evans Hughes, De Jonge v. Oregon, 299 U.S. 353, 365 (1937).
Judicial opinions
Context: Freedom of speech and of the press are fundamental rights which are safeguarded by the due process clause of the Fourteenth Amendment of the Federal Constitution. [... ] The right of peaceable assembly is a right cognate to those of free speech and free press, and is equally fundamental. As this Court said in United States v. Cruikshank, 92 U. S. 542, 552: The very idea of a government, republican in form, implies a right on the part of its citizens to meet peaceably for consultation in respect to public affairs and to petition for a redress of grievances. The First Amendment of the Federal Constitution expressly guarantees that right against abridgment by Congress. But explicit mention there does not argue exclusion elsewhere. For the right is one that cannot be denied without violating those fundamental principles of liberty and justice which lie at the base of all civil and political institutions — principles which the Fourteenth Amendment embodies in the general terms of its due process clause. [... ] These rights may be abused by using speech or press or assembly in order to incite to violence and crime. The people, through their legislatures may protect themselves against that abuse. But the legislative intervention, can find constitutional justification only by dealing with the abuse. The rights themselves must not be curtailed. The greater the importance of safeguarding the community from incitements to the overthrow of our institutions by force and violence, the more imperative is the need to preserve inviolate the constitutional rights of free speech, free press and free assembly in order to maintain the opportunity for free political discussion, to the end that government may be responsive to the will of the people and that changes, if desired, may be obtained by peaceful means. Therein lies the security of the Republic, the very foundation of constitutional government.

“In these great times,” Harry Zohn, trans., In These Great Times (Montreal: 1976), p. 74

Writing in Reason and Passion: Justice Brennan's Enduring Influence (1997).

New York Times (November 28, 1954).
Judicial opinions

p, 125
The History of Freedom in Antiquity (1877)

The Black Coat (2013)

2014, Queensland University Address (November 2014)
Context: America supports free and fair elections, because citizens must be free to choose their own leaders -- as in Thailand where we are urging a quick return to inclusive, civilian rule. We support freedom of assembly, and freedom of speech, and freedom of the press, a free and open Internet, strong civil societies, because the voices of the people must be heard and leaders must be held accountable -- even though it’s uncomfortable sometimes. [... ] We support strong institutions and independent judiciaries and open government, because the rule of force must give way to the rule of law. And in that same fashion, the United States will continue to stand up for the inherent dignity of every human being. Now, dignity begins with the most basic of needs -- a life free of hunger and disease and want.

1900s, A Free Man's Worship (1903)