" In the absence of either a widely accepted theory of language learning or a solid empirical base for classroom practice, teachers and learners have always been, and will always be, vulnerable to drastic pendulum swings of fashion, the coming and going of various unconventional and unlamented "Wonder Methods" being an obvious recent example. The sad truth is that after at least 2,000 years, most language teaching takes place on a wing and a prayer - sometimes successfully, but often a relative failure. "

― , Problems in Second Language Acquisition