What are the themes of the novel Tess of the d'Ubervilles?
Yeah, since you've changed the question :D
Assuming that you're asking what are "themes" in a novel, I would say a theme is the novelist's generalized or discussed universal facts or else a theme has been defined like this;
"Themes are the "keys" to understanding the novel. All novels and poems have themes that the author wants to get across to the reader. If nothing else, a theme is the impression that a reader gets that the book is about. It is not the action of the story, but rather the reader's interpretation of the purpose of the action. A theme can be a moral but it is not the same thing because not all books have traditional morals. Themes are arguably the most important aspect of a novel because they are the reason for the author's writing the novel. Themes are often vague principles or emotions, such as good versus evil, abuse of power, love, change or growing up."