This is not the first attempt to present a new approach to the teaching of second and foreign languages based on a new theory of language. Earlier attempts, most notably audiolingual approaches, have not met with great success. We think that this has happened for several reasons. A major problem was that the theories were not actually theories of language acquisition, but theories of something else; for example, the structure of language. Also, the application of the theory, the methodology, was not always adequately field-tested. What looked reasonable to the university professor on paper did not always work out in the classroom.
The Natural Approach, we hope, does not have these weaknesses. It is based on an empirically grounded theory of second language acquisition, which has been supported by a large number of scientific studies in a wide variety of lanÂ guage acquisition and learning contexts. In addition, it has been used by many classroom teachers in different circumstances teaching various languages and this experience has helped to shape the Approach over the last seven years.
The central hypothesis of the theory is that language acquisition occurs in only one way: by understanding messages. We acquire language when we obtain comprehensible input, when_ we understand what we hear or read in another language. This means that acquisition is based primarily on what we hear and understand, not what we say. The goal, then, of elementary language classes, according to this view, is to supply comprehensible input, the crucial ingredient in language acquisition, and to bring the student to the point where he or she can understand language outside the classroom. When this happens, the acquirer can utilize the real world, as well as the classroom, for progress.
(Parte del prefacio del libro)