When I was studying creative writing at BYU, I had a professor named Brian Evenson who probably made more impact on me than any others there, at least related to my writing. (Overall, Eugene England probably made the most impact on me, interpersonally and getting me interested in Mormon literature.)
Anyway, following is a quote from Brian that I've always remembered, that I agree with as a purpose for literary fiction, and that I've tried to apply to some degree in my recently completed novel manuscript. This is a somewhat edited version of a quote he gave in an interview that was published in Irreantum, a Mormon literary magazine I used to edit.
"As a writer, I gather a useful tension from the fact that I am a believer, but that belief becomes imperceptible in my prose. I don't think that writing, real writing, has much to do with affirming belief—if anything, it causes rifts and gaps in belief which make belief more complex and more textured, more real. Good writing unsettles, destroys both the author and the reader. I see writing as anarchic, as a challenge not only to the notions of order and restraint that impose themselves onto the real but as a challenge to the real itself. Writing, if it is going to be effective, will challenge standard notions of belief. It will tear open gaps and holes where there are weaknesses in the fabric, will call into question received knowledge. But I also think that such writing is finally an affirmation almost in spite of itself. It tears holes, leaves you gutted, but lets you know what won't be torn. It makes things more complex for writer and reader, allows both to move out of the artificial world of Pollyanna."
Also, another quote I find deeply meaningful comes from my most-favorite author ever, John Updike: "I'm willing to show good taste, if I can, in somebody else's living room, but our reading life is too short for a writer to be in any way polite. Since his words enter into another's brain in silence and intimacy, he should be as honest and explicit as we are with ourselves."