“If I am prevented by others from doing what I could otherwise do, I am to that degree unfree; and if this area is contracted by other men beyond a certain minimum, I can be described as being coerced, or, it may be, enslaved.”

Source: The Plague of Fantasies (1997), Chapter One: The Seven Veils of Fantasy, p.9

Atrophied Preface
Naked Lunch (1959)

§5, p. 84
Knots (1970)

Source: The Analects, Chapter I

Attributed in Civilization's Quotations : Life's Ideal (2002) by Richard Alan Krieger, p. 132, and many places on the internet, this was actually stated by Vincent van Gogh in a letter to Anthon van Rappard http://en.wikipedia.org/wiki/Anthon_van_Rappard (18 August 1885) http://vangoghletters.org/vg/letters/let528/letter.html, also rendered "I keep on making what I can’t do yet in order to learn to be able to do it."
Misattributed
Variant: I am always doing that which I cannot do, in order that I may learn how to do it.

The Uttarpara Address (1909)
Context: The second message came and it said, "Something has been shown to you in this year of seclusion, something about which you had your doubts and it is the truth of the Hindu religion. It is this religion that I am raising up before the world, it is this that I have perfected and developed through the Rishis, saints and Avatars, and now it is going forth to do my work among the nations. I am raising up this nation to send forth my word. This is the Sanatan Dharma, this is the eternal religion which you did not really know before, but which I have now revealed to you. The agnostic and the sceptic in you have been answered, for I have given you proofs within and without you, physical and subjective, which have satisfied you. When you go forth, speak to your nation always this word, that it is for the Sanatan Dharma that they arise, it is for the world and not for themselves that they arise. I am giving them freedom for the service of the world. When therefore it is said that India shall rise, it is the Sanatan Dharma that shall be great. When it is said that India shall expand and extend herself, it is the Sanatan Dharma that shall expand and extend itself over the world. It is for the Dharma and by the Dharma that India exists. To magnify the religion means to magnify the country. I have shown you that I am everywhere and in all men and in all things, that I am in this movement and I am not only working in those who are striving for the country but I am working also in those who oppose them and stand in their path. I am working in everybody and whatever men may think or do, they can do nothing but help in my purpose. They also are doing my work, they are not my enemies but my instruments. In all your actions you are moving forward without knowing which way you move. You mean to do one thing and you do another. You aim at a result and your efforts subserve one that is different or contrary. It is Shakti that has gone forth and entered into the people. Since long ago I have been preparing this uprising and now the time has come and it is I who will lead it to its fulfilment."

Source: Diaries of Franz Kafka

But I am a Jew and glad to belong to the Jewish people, though I do not regard it in any way as chosen.

Letter to Central Association of German Citizens of the Jewish Faith, 3 [5] April 1920, as quoted in Alice Calaprice, The Ultimate Quotable Einstein (2010), p. 195; citing Israelitisches Wochenblatt, 42 September 1920, The Collected Papers of Albert Einstein, Vol. 7, Doc. 37, and Vol. 9, Doc 368.
1920s