In fiction, the writer believes that readers will make an effort to follow and interpret an indirectly or abstractly presented progression of theme, whereas the production of nonfiction has more to do with the direct provision of information. Understanding of the potential readers' use for the work and their existing knowledge of a subject are both fundamental for effective nonfiction. Despite the truth of nonfiction, it is often necessary to persuade the reader to agree with the ideas and so a balanced, coherent and informed argument is vital.