“The essential freedom, the ultimate and final freedom that cannot be taken from a man, is to say No. This is the basic premise in Sartre's view of human freedom: freedom is in its very essence negative, though the negativity is also creative.”

Progress, Coexistence and Intellectual Freedom (1968)
Context: Intellectual freedom is essential to human society — freedom to obtain and distribute information, freedom for open-minded and unfearing debate, and freedom from pressure by officialdom and prejudices. Such a trinity of freedom of thought is the only guarantee against an infection of people by mass myths, which, in the hands of treacherous hypocrites and demagogues, can be transformed into bloody dictatorship. Freedom of thought is the only guarantee of the feasibility of a scientific democratic approach to politics, economy, and culture.
But freedom of thought is under a triple threat in modern society—from the deliberate opium of mass culture, from cowardly, egotistic, and philistine ideologies, and from the ossified dogmatism of a bureaucratic oligarchy and its favorite weapon, ideological censorship. Therefore, freedom of thought requires the defense of all thinking and honest people.

Remarks by German Chancellor Angela Merkel before a joint session of Congress on November 04, 2009. http://www.spiegel.de/international/europe/0,1518,659196,00.html
Dokumentation: Angela Merkels Rede im US-Kongress im Wortlaut http://www.welt.de/politik/ausland/article5079678/Angela-Merkels-Rede-im-US-Kongress-im-Wortlaut.html
Context: Freedom is the very essence of our economy and society. Without freedom the human mind is prevented from unleashing its creative force. But what is also clear is that this freedom does not stand alone. It is freedom in responsibility and freedom to exercise responsibility.

1950s, Three Ways of Meeting Oppression (1958)
Context: There is such a thing as the freedom of exhaustion. Some people are so worn down by the yoke of oppression that they give up. A few years ago in the slum areas of Atlanta, a Negro guitarist used to sing almost daily: "Been down so long that down don't bother me." This is the type of negative freedom and resignation that often engulfs the life of the oppressed.

On Kate Bush
The Kate Bush Story (2014)
Context: Creativity comes from the freedom to fail. And freedom to fail comes from experimentation, and that's what gives something its individuality. And, you know, I think her courage, which is the positive way of interpreting it, or bloody-mindedness, which is the negative, is part of what gives her real value as an artist.

Die russische Revolution. Eine kritische Würdigung (1920) p. 109
This contains probably her most famous statement: Freiheit ist immer die Freiheit der Andersdenkenden, translated as "Freedom is always the freedom of dissenters."
Literally: Freedom is always the freedom of those who think differently.

Solway, Diane. “Enforced Disappearance.” W Magazine, November 2011.
2010-, 2011

Source: As quoted in Women Know Everything!: 3,241 Quips, Quotes, & Brilliant Remarks (2007) by Karen Weekes, p. 173

cited in «La destra si riconosca nell'antifascismo» http://www.corriere.it/politica/08_settembre_13/fini_antifascismo_ccb8bcec-8175-11dd-95db-00144f02aabc.shtml, Il Corriere della Sera, 13 September 2008).

Variant translation: The essence of mathematics is in its freedom.
From Kant to Hilbert (1996)