“I write these words in steel, for anything not set in metal cannot be trusted.”

Variant: If a man has to say trust me, Gogu conveyed, it's a sure sign you cannot. Trust him, that is. Trust is a thing you know without words.
Source: Wildwood Dancing

Source: Dash & Lily's Book of Dares

quoted in Marco Belpoliti, " Umberto Eco: How I Wrote my Books http://en.doppiozero.com/materiali/interviste/umberto-eco-how-I-wrote-my-books" (2015)

2000s, 2001, A Great People Has Been Moved to Defend a Great Nation (September 2001)

National Book Award Acceptance Speech (1957)
Context: When a poet is being a poet — that is, when he is writing or thinking about writing — he cannot be concerned with anything but the making of a poem. If the poem is to turn out well, the poet cannot have thought of whether it will be saleable, or of what its effect on the world should be; he cannot think of whether it will bring him honor, or advance a cause, or comfort someone in sorrow. All such considerations, whether silly or generous, would be merely intrusive; for, psychologically speaking, the end of writing is the poem itself.

"The State of the Theatre" an interview by Henry Brandon in Harpers 221 (November 1960)
Context: I cannot write anything that I understand too well. If I know what something means to me, if I have already come to the end of it as an experience, I can't write it because it seems a twice-told tale. I have to astonish myself, and that of course is a very costly way of going about things, because you can go up a dead end and discover that it's beyond your capacity to discover some organism underneath your feeling, and you're left simply with a formless feeling which is not itself art. It's inexpressible and one must leave it until it is hardened and becomes something that has form and has some possibility of being communicated. It might take a year or two or three or four to emerge.