“It is not truth that is validated by a proof, but one’s understanding of it.”

As quoted in The Works of the Emperor Julian (1923) by Wilmer Cave France Wright, p. 311; also in The Paganism Reader (2004) edited by Chas S. Clifton, Graham Harvey, p. 26
General sources

Source: Infinite Jest

"Rousseau & the origins of liberalism," https://www.newcriterion.com/articles.cfm/rousseau-the-origins-of-liberalism-2988 The New Criterion (October 1998).

Curriculum Vitae - an autobiographical statement written when Eisenstein was 20, often referred to as his "Autobiography" (1843)

p, 125
New Fragments (1892)

Account of his famous dream of the benzene structure, as quoted in A Life of Magic Chemistry : Autobiographical Reflections of a Nobel Prize Winner (2001) by George A. Olah, p. 54<!-- also partially quoted in Serendipity, Accidental Discoveries in Science (1989) by Royston M. Roberts , pp. 75-81 -->
Context: I was sitting writing on my textbook, but the work did not progress; my thoughts were elsewhere. I turned my chair to the fire and dozed. Again the atoms were gamboling before my eyes. This time the smaller groups kept modestly in the background. My mental eye, rendered more acute by the repeated visions of the kind, could now distinguish larger structures of manifold conformation; long rows sometimes more closely fitted together all twining and twisting in snake-like motion. But look! What was that? One of the snakes had seized hold of its own tail, and the form whirled mockingly before my eyes. As if by a flash of lightning I awoke; and this time also I spent the rest of the night in working out the consequences of the hypothesis. Let us learn to dream, gentlemen, and then perhaps we shall learn the truth... but let us beware of publishing our dreams before they have been put to the proof by the waking understanding.

[Alan, Dershowitz, http://online.wsj.com/article/SB10001424052702303544604576429783247016492.html?mod=WSJ_Opinion_LEADTop, Casey Anthony: The System Worked, The Wall Street Journal, July 7, 2011, July 7, 2011] published 2011-07-07

I
Variant translation: I am a ridiculous man. They call me a madman now. That would be a distinct rise in my social position were it not that they still regard me as being as ridiculous as ever. But that does not make me angry any more. They are all dear to me now even while they laugh at me — yes, even then they are for some reason particularly dear to me. I shouldn't have minded laughing with them — not at myself, of course, but because I love them — had I not felt so sad as I looked at them. I feel sad because they do not know the truth, whereas I know it. Oh, how hard it is to be the only man to know the truth! But they won't understand that. No, they will not understand.
As translated by David Magarshack
The Dream of a Ridiculous Man (1877)
Context: I am a ridiculous person. Now they call me a madman. That would be a promotion if it were not that I remain as ridiculous in their eyes as before. But now I do not resent it, they are all dear to me now, even when they laugh at me — and, indeed, it is just then that they are particularly dear to me. I could join in their laughter — not exactly at myself, but through affection for them, if I did not feel so sad as I look at them. Sad because they do not know the truth and I do know it. Oh, how hard it is to be the only one who knows the truth! But they won't understand that. No, they won't understand it.

A Short History of Greek Mathematics (1884)