‘In this outstanding collection, leading researchers explore ways in which the rich, complex, and apparently varied phenomena of the languages of the world can be explained in terms of uniform principles of optimal design and external conditions that must be satisfied if language is to be usable at all. Following several different paths, these highly original, carefully crafted, and challenging essays open important new directions for research into some of the most fascinating issues of the study of language, with far-reaching implications beyond.’ Noam Chomsky, Massachusetts Institute of Technology