Quoted from Gates of Excellence: On Reading and Writing Books for Children by Katherine Paterson (56-7):
"Is it true?" the child asks. "Is your story true?"
Ha! you say. We adults don't ask that question because we know you write fiction -- and fiction "is the act of feigning or imagining that which does not exist or is not actual." Ergo -- fiction by definition is not true.
I'm being unfair. Some of you are wiser than that. And although you may never voice the question to the writer, you will come to one of my novels or to anyone's novel with that same question. Is it true?
And my answer for you is the same answer that I give the child who asks. "I hope so. I meant for it to be true. I tried hard to make it so."
...civilization as well as education takes a downward spiral when it ceases to ask, "What is truth?" and concerns itself primarily with what is measurable."