Please excuse the provocative title, and do not misunderstand. Obviously, neither the Pope nor anyone else can change Church doctrine normatively. That is, Church doctrine remains true and unchangeable whatever people--without or within the Church--believe or say. In the same way the teachings of Christ or the Commandments themselves remain true and unchanging. What the Pope can do, however, is to say that Church doctrine has changed or, more to the point, imply by his words or actions that it has. Or he can say or imply that Church doctrine wasn't what most people--including most people in the Church itself...