In The Voyage of the Dawn Treader there is an understood ethical code governing the behavior of the protagonists. The narrator draws our attention to this code of behavior by leaving one character (Eustace) outside of it, contrasting his egotism and supposedly progressive views with the established and wholesome values that everyone else lives by. Some of the principles most relevant to the book's plot include courage, loyalty to one's friends, and individual liberty. Although there are no explicit references to Christianity, the symbolism used in the book and our knowledge of the author's background strongly suggest that the principles in the story are meant to be similar or identical to Christian ideals.
Although Reepicheep is the most honorable character in The Voyage of the Dawn Treader, he is also the most reckless.
The code of behavior that Caspian and the Narnians follow is much like the medieval code of chivalry.