Introduction
This introductory chapter tries to set the chapters to follow in a general background, and to link them together. The first part begins by clarifying what is meant by Universal Grammar (UG), first distinguishing grammar from logic and then UG from a group of related concepts (biolinguistics, the language faculty, competence, I-language, generative grammar, language universals, and metaphysical universals). This leads to a clearer definition of UG as the general theory of I-languages, taken to be constituted by a subset of the set of possible generative grammars, and as such characterizes the genetically determined aspect of the human capacity for grammatical knowledge. The remaining sections introduce each of the five parts of the volume: the philosophical background to UG, linguistic theory, language acquisition, comparative syntax, and a number of wider issues ranging from creoles to animal language.