“It is not hardness of heart or evil passions that drive certain individuals to atheism, but rather a scrupulous intellectual honesty.”

The Notebooks of Leonardo Da Vinci (1938), I Philosophy

Source: Carmilla

Never Give All The Heart http://poetry.poetryx.com/poems/1545/
In The Seven Woods (1904)
Context: Never give all the heart, for love
Will hardly seem worth thinking of
To passionate women if it seem
Certain, and they never dream
That it fades out from kiss to kiss;
For everything that's lovely is
but a brief, dreamy, kind of delight.
O never give the heart outright,
For they, for all smooth lips can say,
Have given their hearts up to the play.
And who could play it well enough
If deaf and dumb and blind with love?
He that made this knows all the cost,
For he gave all his heart and lost.

Letter to John Middleton Murry (5 August 1944), published in The Collected Essays, Journalism, & Letters, George Orwell: As I Please, 1943-1945 (2000), edited by Sonia Orwell and Ian Angus
Context: Of course, fanatical Communists and Russophiles generally can be respected, even if they are mistaken. But for people like ourselves, who suspect that something has gone very wrong with the Soviet Union, I consider that willingness to criticize Russia and Stalin is the test of intellectual honesty. It is the only thing that from a literary intellectual's point of view is really dangerous.

Roger Enrcio, Chief Executive, quoted in [Runkle, Beck Sheetz-, Sun Tzu for Women: The Art of War for Winning in Business, http://books.google.com/books?id=Q9V9mNj0Wd0C&pg=PA112, 18 December 2010, Adams Media, 978-1-4405-1178-3, 112–]

Quoted in Paul Newman: A Life in Pictures, ed. Yann-Brice Dherbier and Pierre-Henri Verlhac (2006), p. 93

Speech delivered in Finney Chapel at Oberlin College (7 February 1957), as reported in "When MLK came to Oberlin" by Cindy Leise, in The Chronicle-Telegram (21 January 2008) http://chronicle.northcoastnow.com/2008/01/21/when-mlk-came-to-oberlin/
1950s
Context: The non-violent Negro is seeking to create the beloved community. He directs his attack on the forces of evil rather than on individuals. The tensions are not between the races, but between the forces of justice and injustice; between the forces of light and darkness.

‘’It Shall Not Be Forgiven’’
Unspoken Sermons, First Series (1867)
Source: Unspoken Sermons: Series I, II, III