“People often think that a fiction is something untrue, but this is wrong. The word derives from the Latin fingere, to make. As something made, fiction is different from something discovered, as in physics, or from something that happened, as in the news. But this does not mean it is false. Fiction is about possible selves in possible worlds.”

The Twilight Zone, "The Fugitive" (1962).
The Twilight Zone

Source: The Collected Stories of Arthur C. Clarke

Six Walks in the Fictional Woods (1994) Chapter Four: "Possible Woods"

2000s, To Live Beyond Our Fear (2007)
Context: We have this window of opportunity; we have a chance to make something real happen. Something possible happen, to live beyond our fear — think about that, and help us. Help lift us up, help us fight this fight to change — transform — this country in a fundamental way.
This chance won’t come around again.

Conversation with George MacBeth on Third Programme (BBC) (1 February 1967), published in The New S.F. (1969), edited by Langdon Jones
Context: I think the new science fiction, which other people apart from myself are now beginning to write, is introverted, possibly pessimistic rather than optimistic, much less certain of its own territory. There's a tremendous confidence that radiates through all modern American science fiction of the period 1930 to 1960; the certainty that science and technology can solve all problems. This is not the dominant form of science fiction now. I think science fiction is becoming something much more speculative, much less convinced about the magic of science and the moral authority of science. There's far more caution on the part of the new writers than there was.

"A Message About Messages" in CBC Magazine https://web.archive.org/web/20051128074549/http://www.cbcbooks.org/cbcmagazine/meet/leguin_ursula_k.html