To most readers the word 'fiction' is an utter fraud. They are entirely convinced that each character has an exact counterpart in real life and that any small discrepancy with that counterpart is a simple error on the author's part. Consequently, they are totally at a loss if anything essential is altered. Make Abraham Lincoln a dentist, put the Gettysburg Address on his tongue, and nobody will recognize it.
Life, Law, and Letters: Essays and Sketches (ed. Houghton Mifflin, 1979)