What are the essential features that permit a sentence to convey a complex idea? What must language users do in order to produce and understand meaningful sentences? And what enables humans, and perhaps apes and robots, to learn this remarkable skill? Janice Moulton and George Robinson offer a fresh and readable approach to these questions. They present an important new theory that clarifies the relationship of language to thought. This theory, which will attract considerable critical attention, combines a general analysis of language with an original cognitive model of syntax and language acquisition; it is a refreshing alternative to recent theories that attempt to formalize all aspects of the relationship of language to thought. The authors provide a helpful review of current theories- including transformational grammar and case theory- and show how they are related to their own 'orrery' and 'syntax crystal' formulations. This book includes a series of simple simulations and 'games' to help readers master the model and test for themselves how well the theory explains the complexities of human language. An appendix describes a computer model that closely follows the authors' description of language processing. This clear account will be of interest to people concerned with language from a variety of perspectives: linguists, cognitive and developmental psychologists, philosophers, computer scientists, and their students will all find it a work of major significance, one that both advances theory and provides a stimulating introduction to the field.