“Could the search for ultimate truth really have revealed so hideous and visceral looking an object?”

Last Exit to Brooklyn (1964)

Source: The Meaning of God in Human Experience (1912), Ch. XIV : The Need of an Absolute, p. 192.
Context: As in reply to the skeptic or agnostic, who asserts in despair that there is no absolute truth. The dialectician retorts: Then at least your own assertion must be absolutely true. There must be some absolute truth, for you cannot assert that there is none without self-contradiction. As in Descartes' case, the doubter is reminded of himself. There, in his own assertion, is a certainty from which he cannot escape.
This turn of thought which reminds the enquirer of himself, we shall call the reflexive turn. It reappears in all discoveries of the Absolute. It is clinching--but is likely to disappoint, even as Descartes' result disappoints. For the skeptic finds that he also was in search of objective truth: and that the absolute truth of his statement is irrelevant to his quest. Whence his skepticism toward objective truth remains unanswered.

Source: Materialism and Empirio-Criticism (1908), p. 130

Source: The Moral Judgment of the Child (1932), Ch. 2 : Adult Constraint and Moral Realism <!-- p. 93 -->
Context: Generally speaking, one can say that motor intelligence contains the germs of completed reason. But it gives promise of more than reason pure and simple. From the moral as from the intellectual point of view, the child is born neither good nor bad, but master of his destiny. Now, if there is intelligence in the schemas of motor adaptation, there is also the element of play. The intentionality peculiar to motor activity is not a search for truth but the pursuit of a result, whether objective or subjective; and to succeed is not to discover a truth.

"Facts Concerning the Late Arthur Jermyn and His Family" - written 1920; first published in The Wolverine, No. 9 (March 1921)
Fiction

In a 1978 interview with John S. Friedman, published in The Paris Review 26 (Spring 1984); and in Elie Wiesel : Conversations (2002) edited by Robert Franciosi, p. 87
Context: Miracles in mysticism don't occupy such an important place. It's metaphor, for the peasants, for the crowds, to impress people. What does mysticism really mean? It means the way to attain knowledge. It's close to philosophy, except in philosophy you go horizontally while in mysticism you go vertically. You plunge into it. Philosophy is a slow process of logic and logical discourse: A bringing B bringing C and so forth. In mysticism you can jump from A to Z. But the ultimate objective is the same. It's knowledge. It's truth.

Tiger and the Rose, 1971

In Search of a Better World (1984)
Context: There are uncertain truths — even true statements that we may take to be false — but there are no uncertain certainties.
Since we can never know anything for sure, it is simply not worth searching for certainty; but it is well worth searching for truth; and we do this chiefly by searching for mistakes, so that we have to correct them.