Prescriptivism is a school of thought that believes that a definite set of rules should be created to control a given language, usually opposed by (and to) Descriptivism. This creates a definite 'right' and 'wrong' in language usage. The language effectively becomes frozen (some would say dead), as the rules define the way the language MUST be used in order to communicate correctly. The upside to this is that the language no longer diverges: odd sentance structures and sytactic styles are stunted in development, allowing all the speakers of the language to clearly communicate. The downside is that the language no longer allows for future development outside of the lexicon, and often creates educational issues and/or classes based on those who know the rules and those who do not.