“The strange and wonderful Book of Job treats of the same subject as we are discussing; its contents are a fiction, conceived for the purpose of explaining the different opinions which people hold on Divine Providence. …This fiction, however, is in so far different from other fictions that it includes profound ideas and great mysteries, removes great doubts, and reveals the most important truths.”

Interview with Weird Tales (24 May 2007) http://weirdtales.net/wordpress/2007/05/24/george-rr-martin-on-magic-vs-science/
Context: I think that for science fiction, fantasy, and even horror to some extent, the differences are skin-deep. I know there are elements in the field, particularly in science fiction, who feel that the differences are very profound, but I do not agree with that analysis. I think for me it is a matter of the furnishings. An elf or an alien may in some ways fulfill the same function, as a literary trope. It’s almost a matter of flavor. The ice cream can be chocolate or it can be strawberry, but it’s still ice cream. The real difference, to my mind, is between romantic fiction, which all these genres are a part of, and mimetic fiction, or naturalistic fiction.

De Abaitua interview (1998)
Context: A god is the idea of a god. The idea of a god is a god. The idea of Glycon is Glycon, if I can enhance that idea with an anaconda and a speaking tube, fair enough. I am unlikely to start believing that this glove puppet created the universe. It’s a fiction, all gods are fiction. It’s just that I happen to think that fiction’s real. Or that it has its own reality, that is just as valid as ours. I happen to believe that most of the important things in the material world start out as fiction. That everything around us was once fiction – before there was the table there was the idea of a table, and the idea of a table before tables was fiction. This is the most important world, the world of fictional things. That’s the world where all this starts.

Source: The Journal of Joyce Carol Oates: 1973-1982

"Tallulah" in Dreams Underfoot : The Newford Collection (2003), p. 399

Attributed to an interview on Larry King Live; also quoted in Quotable Quotes (1997) edited by Deborah Deford
Attributed variant: The difference between fiction and reality is that fiction has to make sense.
Clancy here expresses an idea evoked in similar statements made by others, all derived from the orignial made by Lord Byron:
Lord Byron: Truth is always strange; stranger than fiction.
Mark Twain: Truth is stranger than fiction, but it is because fiction is obliged to stick to possibilities, truth isn't.
G. K. Chesterton: Truth must necessarily be stranger than fiction, for fiction is the creation of the human mind and therefore congenial to it.
Leo Rosten: Truth is stranger than fiction; fiction has to make sense. (attributed)
1990s

The Paris Review interview (2010)
Context: Science Fiction is the fiction of ideas. Ideas excite me, and as soon as I get excited, the adrenaline gets going and the next thing I know I’m borrowing energy from the ideas themselves. Science fiction is any idea that occurs in the head and doesn’t exist yet, but soon will, and will change everything for everybody, and nothing will ever be the same again. As soon as you have an idea that changes some small part of the world you are writing science fiction. It is always the art of the possible, never the impossible.

Variant: For truth is always strange; stranger than fiction.