Some quotes that show Huck's moral growth on the raft relate to his ongoing conflict over whether helping Jim escape is wrong (as society dictates) or right (as his conscience keeps telling him). Earlier in the novel, while Huck and Jim are on the island, Huck continually takes advantage of Jim, tricking him, playing to his superstitions, and really not thinking about Jim as a human being. While they are on the raft together, Huck slowly comes to realize that he and Jim are both human beings and, in fact, Jim is probably a nobler human being than Huck.
From chapter 15, right after Huck returns to the raft. Jim thought Huck had gotten lost, and when Huck returns, he fools Jim into thinking that he (Huck) never left. Huck feels guilty about fooling Jim because Jim is so upset over thinking Huck was dead:
It was fifteen minutes before I could work myself up to go and humble myself to a nigger; but I done it, and I warn't ever sorry for it afterwards, neither. I didn't do him no more mean tricks, and I wouldn't done that one if I'd a knowed it would make him feel that way.
From chapter 16, right after Huck tells some men that there are no runaway "niggers" on the raft, but only his Pap. Huck leads the men to believe that his Pap has smallpox. Huck feels guilting about this but then rationalizes:
Then I thought a minute, and says to myself, hold on; s'pose you'd a done right and give Jim up, would you felt better than what you do now? No, says I, I'd feel bad -- I'd feel just the same way I do now. Well, then, says I, what's the use you learning to do right when it's troublesome to do right and ain't no trouble to do wrong, and the wages is just the same?
From chapter 31, when Huck feels guilty about hiding Jim, he writes Miss Wilson a letter, but becomes so disturbed over the letter, he says:
I took it up, and held it in my hand. I was a-trembling, because I'd got to decide, forever, betwixt two things, and I knowed it. I studied a minute, sort of holding my breath, and then says to myself: "All right, then, I'll go to hell" -- and tore it up.
As you look for some quotes that show how Huck regresses on land, look for chapters in which he actually IS on land - at the beginning of the novel in Miss Wilson's home, while with Pap, on land with the duke and the king, on land in the midst of the feud, etc.
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