In this major new book John A. Hawkins presents a new theory of linear ordering in syntax. He argues that processing can provide a simple, functional explanation for syntactic rules of ordering, as well as for the selection among ordering variants in languages and structures in which variation is possible. Insights from generative syntax, typological studies of language universals, and psycholinguistic studies of language processing are combined to show that there is a profound correspondence between performance and grammar. The major ordering principle proposed, Early Immediate Constituents, is tested on performance data from ten distinct languages. The result is a unified theory of free and fixed word orders, in which ordering is driven by efficient structure recognition. This major work will be welcomed by a wide cross-section of readers in syntax, language typology, psycholinguistics, and cognitive science.