My local book club read Umberto Eco's In the Name of the Rose. While the book itself is a mixed bag through which I struggled (which is not an indictment of the novel, since I struggled through Moby Dick as well), there's a remarkable chapter about the origin of heresy. If you don't want to read the novel, it's worth borrowing it off the library or bookstore shelf and turning to Second Day, Chapter Nones (p. 196). Here are some highlights of the dialogue between William of Baskerville and his novice Adso of Melk.