Evasion is a central theme of the first twenty-five chapters of the novel. Huck opens the book narrating his experiences with the widow, which include occasional escapes back into nature.
Huck soon escapes from his father, faking his own death, then evades discovery along with Jim. Jim is also on the run, evading the authorities.
As they go along down the river, Huck often has to take recourse in lies and deception. This is another form of evasion.
More themes developed in this section of the novel include: freedom (specifically, freedom from abuse); identity (specifically, identity as generated by society).