“Freedom, privileges, options, must constantly be exercised, even at the risk of inconvenience. Otherwise they fall into desuetude and become unfashionable, unorthodox—finally irregulationary.”

On Manners and Fashion
Essays on Education (1861)

Source: So Long, and Thanks for All the Fish

Closing remarks in court https://www.youtube.com/watch?v=GGIbb8rY7hQ&feature=youtu.be (1 June 2011)
2010s

Source: 1990s, Against the Grain (1990), p. 172

On polygyny is Islam.
The World's Religions (1991)
Context: There are circumstances in the imperfect condition we know as human existence when polygyny is morally preferable to its alternative. Individually, such a condition might arise if, early in the marriage, the wife were to contract paralysis or another disability that would prevent sexual union. Collectively, a war that decimated the male population could provide an example, forcing (as this would) the option between polygyny and depriving a large population of women of motherhood and a nuclear family of any sort. Idealists may call for the exercise of heroic continence in such circumstances, but heroism is never a mass option.

Source: Up From Slavery: An Autobiography

Nota en Clarin 25/04/2006 http://www.clarin.com/diario/2006/04/25/um/m-01184158.htm
Unsourced, 2006

Address http://www.ted.com/talks/james_cameron_before_avatar_a_curious_boy.html/ to the 2010 TED conference (13 February 2010)
Context: Imagination is a force that can actually manifest a reality. … Don’t put limitations on yourself. Other people will do that for you. Don’t do that to yourself. Don’t bet against yourself. And take risk. NASA has this phrase that they like, "Failure is not an option." But failure has to be an option. In art and exploration, failure has to be an option. Because it is a leap of faith. And no important endeavour that required innovation was done without risk. You have to be willing to take those risks. … In whatever you are doing, failure is an option. But fear is not.

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.