“The single merit I can claim at this junction is that I am not seeking to obtain agreement. I am seeking only to outline the reality that exists, not to win support, start a movement, or contrive concurrence. The reason is clear. It can’t be done. Additionally I do not know everything. Therefore, I can be wrong. What evil I could impose if I obtain agreement on a point that happened to be in error! I do not intend to be wrong, but the mind and the memory are both fallible. So I propose to set down what is so, to the degree I am capable of recognizing it.”

Statement published in A Year of Beautiful Thoughts‎ (1902) by Jeanie Ashley Bates Greenough, p. 172, Third statement for June 11. This has often been misattributed to Helen Keller in some published works since at least 1980, perhaps because she somewhere quoted it.
Variant:
I am only one,
But still I am one.
I cannot do everything,
But still I can do something;
And because I cannot do everything,
I will not refuse to do the something that I can do.
The Book of Good Cheer : A Little Bundle of Cheery Thoughts‎ (1909) by Edwin Osgood Grover, p. 28; also in Masterpieces of Religious Verse (1948) by James Dalton Morrison, p. 416, where it is titled "Lend a Hand"
Variant: I am only one, but still I am one. I cannot do everything, but still I can do something; and because I cannot do everything, I will not refuse to do something that I can do.

Statement published in A Year of Beautiful Thoughts‎ (1902) by Jeanie Ashley Bates Greenough, p. 172, Third statement for June 11. This has often been misattributed to Helen Keller in some published works since at least 1980, perhaps because she somewhere quoted it.
Variant:
I am only one,
But still I am one.
I cannot do everything,
But still I can do something;
And because I cannot do everything,
I will not refuse to do the something that I can do.
The Book of Good Cheer : A Little Bundle of Cheery Thoughts‎ (1909) by Edwin Osgood Grover, p. 28; also in Masterpieces of Religious Verse (1948) by James Dalton Morrison, p. 416, where it is titled "Lend a Hand"

Attributed by Thomas Babington Macaulay, Life of Frederick the Great (1882), pg 48.
Repeated by Thomas Babington Macaulay in a review of "Frederick the Great and his Times. Edited, with an Introduction, by Thomas Campbell, Esq". Edinburgh Review, ISSN 1751-8482, 04/1842, Volume 75, Issue 151, p. 241-242, though it does not appear in the original work.
Knowles, Oxford Dictionary Of Quotations (5th Edition) (Oxford University Press, 1999)
Attributed

The Tragic Sense of Life (1913), II : The Starting-Point

UN Address (1999)
Context: For many years, I did my best to report on the issues of the day in as objective a manner as possible. When I had my own strong opinions, as I often did, I tried not to communicate them to my audience.
Now, however, my circumstances are different. I am in a position to speak my mind. And that is what I propose to do.
Those of us who are living today can influence the future of civilization. We can influence whether our planet will drift into chaos and violence, or whether through a monumental educational and political effort we will achieve a world of peace under a system of law where individual violators of that law are brought to justice.

The Diary of Samuel Marchbanks (1947)
Context: I don't really care how time is reckoned so long as there is some agreement about it, but I object to being told that I am saving daylight when my reason tells me that I am doing nothing of the kind. I even object to the implication that I am wasting something valuable if I stay in bed after the sun has risen. As an admirer of moonlight I resent the bossy insistence of those who want to reduce my time for enjoying it. At the back of the Daylight Saving scheme I detect the bony, blue-fingered hand of Puritanism, eager to push people into bed earlier, and get them up earlier, to make them healthy, wealthy and wise in spite of themselves.

§5, p. 84
Knots (1970)

Source: "Viktor Yanukovych accepts blame for Ukraine bloodshed, defends zoo" in The Sydney Morning Herald https://www.smh.com.au/world/viktor-yanukovych-accepts-blame-for-ukraine-bloodshed-defends-zoo-at-his-residence-20150623-ghvvj9.html (24 June 2015)