There are perhaps a number of reasons. It is clear that changes in approaches to teaching have no single cause. They come about partly in response to changing perceptions of good language use, partly in response to developments in linguistics, and partly in response to changing political and demographic circumstances. Success in language learning, moreover; is not an absolute category. It varies with the values of the age and with many other factors besides, for example, what the language is to be used for, by whom, and in what circumstances. Answers to applied linguistics problems, in other words, if this one is any thing to go by, are not likely to be stable, final, or value-free.