What is it about the human mind that accounts for the fact that we can all speak and understand a language? Why can't other creatures do the same? And what does this tell us about the rest of a human abilities? Recent dramatic discoveries in linguistics and psychology provide intriguing answers to these age-old mysteries. In this fascinating book, Ray Jackendoff emphasizes the grammatical commonalities across languages, both spoken and signed, and discusses the implications for our understanding of language acquisition and loss.