“At this moment the most stable Government in the world is our own, and it is solely because, in its real essence, it is the most free, in the only sense in which Freedom really exists; where men can act at their own free discretion, restrained only by the necessities of Justice. If the spirit of the Constitution is to be observed, that great instrument is always self-preserving. It needs only to be followed to be safeguarded.”

Source: Life, the Truth, and Being Free (2010), p. 26

I Am Running for President in Turkey. From My Prison Cell. (2018)

Book II, Chapter 5, p. 280
The Origin of Consciousness in the Breakdown of the Bicameral Mind (1976)

The Passionate State Of Mind, and Other Aphorisms (1955)

Listen, Little Man! (1948)
Context: Every physician, shoemaker, mechanic or educator must know his shortcomings if he is to do his work and make his living. For some decades, you have begun to play a governing role on this earth. It is on your thinking and your actions that the future of humanity depends. But your teachers and masters do not tell you how you really think and are; nobody dares to voice the one criticism of you which could make you capable of governing your own fate. You are "free" only in one sense: free from education in governing your life yourself, free from self-criticism.

Speech in Hillsdale, Michigan, February 7, 2004. http://renewamerica.us/archives/speeches/04_02_07hillsdale.htm.
2009

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.

As quoted in The Best Liberal Quotes Ever : Why the Left is Right (2004) by William P. Martin. Though widely attributed to Henry, this statement has not been sourced to any document before the 1990s and appears to be at odds with his beliefs as a strong opponent of the adoption of the US Constitution.
Misattributed

1900s, Inaugural Address (1905)
Context: The conditions which have told for our marvelous material well-being, which have developed to a very high degree our energy, self-reliance, and individual initiative, have also brought the care and anxiety inseparable from the accumulation of great wealth in industrial centers. Upon the success of our experiment much depends, not only as regards our own welfare, but as regards the welfare of mankind. If we fail, the cause of free self-government throughout the world will rock to its foundations, and therefore our responsibility is heavy, to ourselves, to the world as it is to-day, and to the generations yet unborn.