“I suppose, in the end, we journalists try - or should try - to be the first impartial witnesses of history. If we have any reason for our existence, the least must be our ability to report history as it happens so that no one can say: 'we didn't know - no one told us.”

On the absence of people of color in her school curriculums in “‘My Writing is My Activism’: An Interview with Isabel Quintero” https://lareviewofbooks.org/article/my-writing-is-my-activism-an-interview-with-isabel-quintero/ in Los Angeles Review of Books (2017 Feb 1)

2010s, Hard Truths: Law Enforcement (2015)

Department of Defense news briefing (12 February 2002)
Variant:
Now what is the message there? The message is that there are no "knowns." There are things we know that we know. There are known unknowns. That is to say there are things that we now know we don't know. But there are also unknown unknowns. There are things we do not know we don't know. So when we do the best we can and we pull all this information together, and we then say well that's basically what we see as the situation, that is really only the known knowns and the known unknowns. And each year, we discover a few more of those unknown unknowns.
:It sounds like a riddle. It isn't a riddle. It is a very serious, important matter.
:There's another way to phrase that and that is that the absence of evidence is not evidence of absence. It is basically saying the same thing in a different way. Simply because you do not have evidence that something exists does not mean that you have evidence that it doesn't exist. And yet almost always, when we make our threat assessments, when we look at the world, we end up basing it on the first two pieces of that puzzle, rather than all three.
:* Extending on his earlier comments in a press conference at NATO Headquarters, Brussels, Belgium (6 June 2002) http://www.nato.int/docu/speech/2002/s020606g.htm
2000s

Reported in Didi Kirsten Tatlow, "A System Afraid of Its Own History", The New York Times (September 16, 2010).

2015, Remarks to the Kenyan People (July 2015)

Injunctions of Marx
Specters of Marx (1993)

Speech to the United States House of Representatives (July 2015)

As quoted in The Journal of Imaging Science and Technology, Vol. 37, No. 3 (1992), p. 537
Context: There's a tremendous popular fallacy which holds that significant research can be carried out by trying things. Actually it is easy to show that in general no significant problem can be solved empirically, except for accidents so rare as to be statistically unimportant. One of my jests is to say that we work empirically — we use bull's eye empiricism. We try everything, but we try the right thing first!

Todo lo que nos sucede, todo lo que hablamos o nos es relatado, cuanto vemos con nuestros propios ojos o sale de nuestra lengua o entra por nuestros oídos, todo aquello a lo que asistimos (y de lo cual, por tanto, somos algo responsables), ha de tener un destinatario fuera de nosotros mismos, y a ese destinatario lo vamos seleccionando en función de lo que acontece o nos dicen o bien decimos nosotros.
Source: Todas las Almas [All Souls] (1989), p. 140