The theme of Mark Twain's Huckleberry Finn is that the ideas of society can greatly influence the individual, and sometimes the individual must break off from the accepted values of society to determine the ultimate truth for himself. In Huckleberry Finn's world, society has corrupted justice and morality to fit the needs of the people of the nation at that time. Basically, Americans were justifying slavery, through whatever social or religious ways that they deemed necessary during this time.
The conflict between society and Huckleberry Finn results from Huck's non-conformist attitude. This attitude is a result of his separation from society at an early age. With a highly abusive drunkard for a father, Huckleberry Finn is forced from childhood to rely solely on himself. As a result of this, he effectively alienates himself from the rest of society. Society continues to try to "reform" him, but Huckleberry Finn shows his lack of appreciation in that effort from the very beginning of the story when he says, "The Widow Douglas she took me for her son, and allowed she would sivilize me I got into my old rags and my sugar hogshead again, and was free and satisfied." His actions are based on instinct and his own experience, rather than conventional conscience. As a result, he makes up the rules for himself as he goes along, forming a conscience that is keenly aware of society's prejudices but actions based on that which he has experienced.
Ironically, often his own instincts hold him to a higher moral standard than those of society. His decision to help free Jim, a slave, is an example of one such instance. Huckleberry Finn recognizes Jim as a human being, but is fighting the beliefs bestowed upon him by a society that believes slaves should not be free. However, it is important to realize that although Huckleberry Finn's decisions create the conflict between society and himself (and that this conflict forms the theme of the novel), Huck is oblivious to the justice, the righteousness, and even the heroism of his own actions, they are simply in accordance with his own conscience.
The climax comes in chapter thirty-one of the novel, when...