This character is a slave. For most people living in the pre-Civil War south, that's about all there is to know. Who cares about a slave, his motivations, character, background, or feelings? It would be like trying to psychoanalyze your family pet (yes, they contrasted animals and Afro-Americans. Period of total racism). But Twain is smarter than that—and so is Huck. Jim is a bit of a complex character as Huck is, and maybe even more. His character is loyal and superstitious.
Jim Upton in the Essays