“I am not accustomed to saying anything with certainty after only one or two observations.”

Journal for Saturday, 27th November 1813; Quoted in Letters and Journals of Lord Byron by Thomas Moore (1830), Vol III, Chap. XVII, p. 208 http://books.google.com/books?id=nloLAAAAIAAJ&pg=PA208

Variant: It's only after we've lost everything that we're free to do anything.
Source: Fight Club

Upon finding yet another obscured and deadly abyss
Sydpolen (The South Pole) (1912)

Encountering Directors interview (1969)

Teaching as a Subversive Activity (1969)
Context: In order to understand what kind of behaviors classrooms promote, one must become accustomed to observing what, in fact, students actually do in them. What students do in a classroom is what they learn (as Dewey would say), and what they learn to do is the classroom's message (as McLuhan would say). Now, what is it that students do in the classroom? Well, mostly they sit and listen to the teacher. Mostly, they are required to believe in authorities, or at least pretend to such belief when they take tests. Mostly they are required to remember. They are almost never required to make observations, formulate definitions, or perform any intellectual operations that go beyond repeating what someone else says is true. They are rarely encouraged to ask substantive questions, although they are permitted to ask about administrative and technical details. (How long should the paper be? Does spelling count? When is the assignment due?) It is practically unheard of for students to play any role in determining what problems are worth studying or what procedures of inquiry ought to be used. Examine the types of questions teachers ask in classrooms, and you will find that most of them are what might technically be called "convergent questions," but what might more simply be called "Guess what I am thinking " questions.

When asked about his speculations on life beyond death, as quoted in The Homiletic Review‎ (April 1896), p. 442
Context: Speculations? I have none. I am resting on certainties. I know whom I have believed and am persuaded that he is able to keep that which I have committed unto him against that day.

U.S. Grant's "perfect speech" which he used on several occasions beginning in 1865, as quoted in Grant: A Biography (1982) by William S. McFeely, p. 234.
1860s
Context: I rise only to say that I do not intend to say anything. I thank you for your hearty welcomes and good cheers.

State of Fear (2004)