This way the first paragraph helps the reader understand why the writer is writing. A thesis should be narrow in focus in order to allow the fullest exploration of its issues as possible, and it should reflect the type of paper that follows, whether it be persuasive or informative. Narrowing the focus of the thesis may require posing questions about it to yourself before committing to a final version. A good writer can assert the main idea of a short, coherent essay briefly. Instead of rambling, be as straightforward as possible.
Few writers finish a paper writing about the exact topic they begin with.
While you write a paper, your main point may change. As you're finishing, make sure your thesis statement has changed along with the subject and controlling ideas of your paper.