Kohlberg states that people go through three different steps of morality in ascending order as we mature into adults. We start off at Step 1, Preconventional Morality. We think about whether we will get punished or rewarded for something. Step 2 is Conventional Morality. We think about how our community will view us. Step 3, is Postconventional Morality. What you feel is right and wrong.
If Mark Twain were alive in Kohlberg's day, he would see things a little different. In "The Adventures of Hucklberry Finn", Huck frees a slave from his master. Most of the adults he met, had they all known, would have felt he had sinned. Huck Finn was stealing another mans property (a slave). Huck believed he would go to hell for freeing a slave. He was willing to sacrifice his soul, make the community very angry with him, and get punished for what he felt was doing the right thing.
Huck displayed the ability to move beyond the first two conventions and make decisions on the highest. A pattern in Mark Twain's books dealt with children in his stories doing the right thing, and the older people being too corrupt to do so. Mark Twain would agree with the order of Kohlberg's morality and the different types, but would believe we would go from step 1 to step 3, and as adults conform to societal norms falling to step 2, a lower moral thought process.