Q: What is the difference between a main idea and a theme? A main idea typically relates to nonfiction works such as essays. In a good essay, the main idea of each paragraph is directly stated. For example, in an essay about the need for more public transportation options in the United States, the main idea of one of the supporting paragraphs might be "Private automobiles have been one of the biggest contributors to global warming." A theme, on the other hand, typically refers to a work of fiction and is almost never directly stated. Rather, writers use symbols to represent the theme throughout a work. It is up to the reader to detect the theme by connecting the clues that the author inserts. Main ideas often support a subject; themes require making inferences. In this context, main ideas are more direct while themes are more abstract.