A hypothesis, or claim, is a statement concerning the main idea or point the author is trying to prove in his writing. Each author in this book presents evidence in support of one of two hypotheses: either that vampires are real or that vampires are a fiction. An author uses a hypothesis as a way to explain the series of facts or evidence he will use to prove his hypothesis about vampires is the correct one. The facts and evidence supporting the author's claims can then be tested for accuracy by further investigation or research.

How does the hypothesis work in practice? Based on experience or research, an author may hypothesize that vampires are real. The author's questions or ideas about vampires will guide his or her further research. The author will look for information that will...