Theme is easily defined as the main idea of a story. The author had written a certain literary work for a purpose. However it is surprisingly amazing that each reader ends up with a theme that is slightly different from the author's intention. This, of course, is unavoiable because people aren't the same. Thus despite a group of people read an identical book, the main idea that they feel is the most important or the lesson the've learned is diferent from each other. Needless to say that the theme must be based on the given text. In other words, a reader can finish a book with a theme that is totally opposite to the writer's.