“I amuse myself, not by making people believe what I wish, but by letting them believe what they wish. These fools of Parisians declare that I am five hundred, and I confirm them in the idea since it pleases them.”

Source: Finite and Infinite Games: A Vision of Life as Play and Possibility

As quoted in The Tyrants: 2500 Years of Absolute Power and Corruption (2006) by Clive Foss ISBN 1905204965
Undated

James Beattie, letter of May 25, 1780, published in William Forbes An Account of the Life and Writings of James Beattie, LL.D. (1806) p. 331.
In reply to Lord Kinnoull, who had complimented him on his Messiah, "the noble entertainment which he had lately given the town". Beattie had this on the authority of Kinnoull himself.

recollection http://darwin-online.org.uk/content/frameset?itemID=F2113&viewtype=text&pageseq=7 by E. Ray Lankester, from his essay "Charles Robert Darwin" in C.D. Warner, editor, Library of the World's Best Literature: Ancient and Modern (R.S. Peale & J.A. Hill, New York, 1896) volume 2, pages 4835-4393, at page 4391
Other letters, notebooks, journal articles, recollected statements

Rawstory.com Interview (9 September 2005) http://rawstory.com/news/2005/Zinn_interview_part_two_Same_arguments_made_in_Vietnam_made_0909.html, which compares U.S. wars in Iraq and Vietnam
Context: I would encourage people to look around them in their community and find an organization that is doing something that they believe in, even if that organization has only five people, or ten people, or twenty people, or a hundred people. And to look at history and understand that when change takes place it takes place as a result of large, large numbers of people doing little things unbeknownst to one another. And that history is very important for people to not get discouraged. Because if you look at history you see the way the labor movement was able to achieve things when it stuck to its guns, when it organized, when it resisted. Black people were able to change their condition when they fought back and when they organized. Same thing with the movement against the war in Vietnam, and the women's movement. History is instructive. And what it suggests to people is that even if they do little things, if they walk on the picket line, if they join a vigil, if they write a letter to their local newspaper. Anything they do, however small, becomes part of a much, much larger sort of flow of energy. And when enough people do enough things, however small they are, then change takes place.

Source: Final Analysis (1990), p. 183

Source: Autobiography of Mark Twain, Vol. 3 (2015), p. 288