“The trite and the extravagant are the Scylla and Charybdis of writers who deal in fiction,” Coleridge wrote in 1794, in a review of Ann Radcliffe's The Mysteries of Udolpho. Thomas Hardy once made a similar point --
“The whole secret of fiction and the drama --in the constructional part -- lies in the adjustment of things unusual to the things eternal and universal. The writer who knows exactly how exceptional and how non-exceptional his events should be made, possesses the key to the art.”
Here's how Samuel R. Delany puts it in About Writing --
“Writers are always grappling with two problems: they must make the story interesting (to themselves, if no one else), yet keep it believable (because, somehow, when it ceases to be believable on some level, it ceases to be interesting).”
Delany goes on,”Keeping things interesting seems to be primarily the province of the conscious mind (which, from the literature available, we know far less about than the unconscious), while believability is something that is supplied, in the images it throws up into the mind's theater, primarily by the unconscious.”
I have often wondered why fiction is more believable than non-fiction, and I think Delany gives us the answer here -- more of fiction is supplied by the unconscious mind, which is where emotional certainty comes from, cf. my earlier posts about Robert Burton's On Being Certain, here and here. “Believability” in this context isn't about statistical probability, because your unconscious mind believes in a lot of things your conscious mind hopefully doesn't. Magic, for example -- otherwise fantasy novels wouldn't sell.
I heard Douglas Adams say on the radio once that you don't decide what you think about something, and then put it into a novel – rather you write a novel because that's the only way to find out what you think about something. Another comment that's stuck with me: interviewed about his story “Pity” in Best American Short Stories 1995, Avner Mandelman said that the way to write a story was to take something you think you believe and prove it wrong in a story.
Then writing fiction is a way to find out what you unconsciously believe...