“If I don’t speak truth I can’t seek truth.”

Introductio ad prudentiam: Part II (1727), Gnomologia (1732)

Cuando tú y la verdad me hablan, no escucho a la verdad. Te escucho a ti.
Voces (1943)

Looking for an Honest Man (2009)
Context: Diogenes … refuses to be taken in by complacent popular belief that we already know human goodness from our daily experience, or by confident professorial claims that we can capture the mystery of our humanity in ­definitions. But mocking or not, and perhaps speaking better than he knew, Diogenes gave elegantly simple expression to the humanist quest for self-knowledge: I seek the human being — my human being, your human being, our humanity. In fact, the embellished version of Diogenes' question comes to the same thing: To seek an honest man is, at once, to seek a human being worthy of the name, an honest-to-goodness exemplar of the idea of humanity, a truthful and truth-speaking embodiment of the animal having the power of articulate speech.

Life-Line (p. 16)
Short fiction, The Past Through Tomorrow (1967)

Source: Dead of Winter

Introduction.
Race and Democratic Society (1945)

Source: The Repossession Mambo (2009), Chapter 19 (p. 292)

"La Paquet Rouge" in Opéra (1925)

On doit exiger de moi que je cherche la vérité, mais non que je la trouve.
No. 29; Variant translation: I can be expected to look for truth but not to find it.
Pensées Philosophiques (1746)