This is a collection of essays on the native and non-native acquisition of syntax within the Principles and Parameters framework. In line with current methodology in the study of adult grammars, language acquisition is studied here from a comparative perspective. The unifying theme is the issue of the 'initial state' of grammatical knowledge: For native language, the important controversy is that between the Continuity approach, which holds that Universal Grammar is essentially constant throughout development, and the Maturation approach, which maintains that portions of UG are subject to...