The aim of this study is to show that a self-contained linguistic theory cannot by itself be psychologically plausible, but depends on a compatible theory of learning which embraces developmental as well as formal issues.
Preface; 1. The problem of language learnability; 2. The components of the linguistic system; 3. The components of the learning system; 4. Approaches to parameter fixation; 5. The scope and limits of the current approaches; 6. The distribution and variety of null subjects; 7. Augmented parameter fixation: pro subjects and learnability.