“In order to understand information, we must define it; bit in order to define it, we must first understand it. Where to start?”

Ask the Awakened: the Negative Way (1963)

Source: War and Peace

Source: Sex and Character (1903), p. 105.

Michael Korda, in Success! (1977), p. 284
Misattributed

1960s, Where Do We Go from Here: Chaos or Community? (1967)
Context: Now, in order to answer the question, "Where do we go from here?" which is our theme, we must first honestly recognize where we are now. When the Constitution was written, a strange formula to determine taxes and representation declared that the Negro was sixty percent of a person. Today another curious formula seems to declare that he is fifty percent of a person. Of the good things in life, the Negro has approximately one half those of whites. of the bad things of life, he has twice those of whites. Thus half of all Negroes live in substandard housing. And Negroes have half the income of whites. When we view the negative experiences of life, the Negro has a double share. There are twice as many unemployed. The rate of infant mortality among Negroes is double that of whites and there are twice as many Negroes dying in Vietnam as whites in proportion to their size in the population.

"Reflections and Anecdotes", nr. 264 (Douglas Parmée translation)

The Idiot (1868–9)
Context: Nor is there any embarrassment in the fact that we're ridiculous, isn't it true? For it's actually so, we are ridiculous, light-minded, with bad habits, we're bored, we don't know how to look, how to understand, we're all like that, all, you, and I, and they! Now, you're not offended when I tell you to your face that you're ridiculous? And if so, aren't you material? You know, in my opinion it's sometimes even good to be ridiculous, if not better: we can the sooner forgive each other, the sooner humble ourselves; we can't understand everything at once, we cant start right out with perfection! To achieve perfection, one must first begin by not understanding many things! And if we understand too quickly, we may not understand well. This I tell you, you, who have already been able to understand... and not understand … so much. I'm not afraid for you now;

Source: Tertium Organum (1912; 1922), Ch. I
Context: The most difficult thing is to know what we do know, and what we do not know.
Therefore, desiring to know anything, we shall before all else determine WHAT we accept as given, and WHAT as demanding definition and proof; that is, determine WHAT we know already, and WHAT we wish to know.
In relation to the knowledge of the world and of ourselves, the conditions would be ideal could we venture to accept nothing as given, and count all as demanding definition and proof. In other words, it would be best to assume that we know nothing, and make this our point of departure.
But unfortunately such conditions are impossible to create. Knowledge must start from some foundation, something must be recognized as known; otherwise we shall be obliged always to define one unknown by means of another.

AJENCIS, THE THIRD ANALYTIC OF MEN
The Darkness That Comes Before (2004)