Edward Abbey said this quote

The novel should tell the truth, as I see the truth, or as the novelist persuades me to see it. And one more demand: I expect the novelist to aspire to improve the world. ... As a novelist, I want to be more than one more dog barking at the other dogs barking at me. Not out of any foolish hope that one novelist, or all virtuous novelists in chorus, can make much of a difference for good, except in the long run, but out of the need to prevent the human world from relaxing into something worse. To maintain the tension between truth and falsity, beauty and ugliness, good and evil. ... I believe the highest duty of the serious novelist is, whatever the means or technique, to be a critic of his society, to hold society to its own ideals, or if these ideals are unworthy, to suggest better ideals.