If you set to work to believe everything, you will tire out the believing-muscles of your mind, and then you'll be so weak you won't be able to believe the simplest true things.
(Lewis Carroll [Charles Lutwidge Dodgson] (1832-1898), British author, mathematician, clergyman. Letter, May 23, 1864, to Mary MacDonald, daughter of the poet-novelist George MacDonald. The Letters of Lewis Carroll, vol. I, ed. Morton N. Cohen, Oxford University Press (1979).)
Belief in the truth commences with the doubting of all those "truths" we once believed.
(Friedrich Nietzsche (1844-1900), German philosopher, classical scholar, critic of culture. Friedrich Nietzsche, Sämtliche Werke: Kritische Studienausgabe, vol. 2, p. 387, eds. Giorgio Colli and Mazzino Montinari, Berlin, de Gruyter (1980). Mixed Opinions and Maxims, aphorism 20, "Truth Will Have No Other Gods Alongside It," (1879).)
I don't believe that you have to be a cow to know what milk is.
(Ann Landers (b. 1918), U.S. advice columnist. As quoted in Time (August 21, 1989).
Explaining why, despite her untroubled Midwestern upbringing, she felt qualified to advise people with serious problems.)
We believe ... that the applause of silence is the only kind that counts.
(Alfred Jarry (1873-1907), French playwright, author. repr. in The Selected Works of Alfred Jarry, eds. Roger Shattuck and Simon Watson Taylor (1965). "Twelve Theatrical Topics," topic 12, published in Dossiers Acénonètes due Collège de 'Pataphysique, no. 5 (1960).)