The Mississippi River is used as a symbol of Huck’s conscience and moral development. As Huck moves along the river, he grows as a person.
In the beginning, Huck is a simple country boy. An orphan who has run away from his abusive father, Huck is left with nothing but the river and a raft. When he finds Jim, he begins his journey. On the river, Huck is at peace. Yet he also learns many important lessons about life.
As Huck travels down the river, he explores his conscience. He is troubled by it. He knows that helping Jim is wrong. At the same time, he is confused. Jim is a good friend. He is a good person. How can helping him be wrong? Huck struggles with his conscience. He feels that he will go to Hell for helping Jim. Yet he decides he might as well go to Hell then.
But that's always the way; 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. (ch 33)
Huck learns lessons about friendship, such as when it is and is not okay to play a trick on someone. When he pretends that Jim dreamed they were separated and Jim gets upset, he feels bad. He realizes that it was not an okay trick to play on anyone. Similarly, he disagrees with the antics of the King and the Duke, and tries to help the family they swindle.
Huck’s greatest test comes when he finds out that Tom knew that Jim was free the whole time they were trying to help him escape. Huck decides he does not need civilization, if that is what it means. He goes off on his own, because his journey down the river alone with Jim is the only part of his life that has ever made sense.