Caliban is a character who represents the complex nature of good and evil. Because he is described as a "monster" and his ugly appearance is referred to frequently, he is characterized as being of negative moral character. But his behavior often displays qualities that go against this assessment: for example, he displays a noble intelligence, and a pronounced sense of loyalty and honor at times. Compared to Ariel, who is often capricious and behaves in ways that may be seen as morally ambiguous, Caliban could be seen as morally superior. But his appearance works against this characterization, and that is one of the play's major themes. This concept of good and evil being based on appearances is also related to Prospero's attempts to shelter Miranda from the world of men, who he believes may corrupt his daughter.