Morality is at the heart of this novel as Huck attempts to navigate two contrasting and conflicting moral views.
Raised to believe that the law is sanctified, Huck feels that he is beholden to society's moral code. However, he is also drawn to break this code repeatedly. Yet, every time he feels that he has transgressed against society's morality he feels guilty and conscience-stricken.
The primary example of this can be found in Huck's temptation to turn Jim over to the authorities as the two head down river. Huck feels that he is helping to steal someone else's property by helping Jim run away. Society's moral code suggests that Huck is doing some thing low and evil.
Huck's personal moral code presents a different picture entirely.
Huck understands that Jim loves his wife and wants to be with his family. He is a person with feelings, affections, and desires. Helping Jim is the natural thing to do. In helping Jim, Huck is not really hurting anyone.
Thus, Huck has a moral dilemma on his hands. As he articulates clearly, conscience will dog him no matter what he chooses.
"...it don't make no difference whether you do right or wrong, a person's conscience ain't got no sense, and just goes for him anyway."