What is the theme in Northanger Abbey by Jane Austen?

A dominant theme within the novel concerns an examination of social propriety. Young Catherine is too naïve to actually know which of her behaviors are potentially scandalous and which are fully acceptable. Thus, she accepts an invitation to ride with John without realizing her behavior might not be completely proper. Later, Mrs. Allen gently suggests that a repeat performance might not be the best thing. Throughout the period spent in Bath, Catherine is always conscious of her own behavior and worries about how others might perceive it—but she has no foundation upon which to accurately judge herself. Other characters, too, are highly concerned with social appearances.