Stratal Optimality Theory (SOT) is a comprehensive theory of sound structure and its relation to word structure that integrates the complementary theoretical insights of lexical phonology and classical optimality theory. Paradigms and Opacity explores the many facets of SOT. Volume One focuses on constraint interaction and provides a principled solution to the problem of opacity:  how, why, and when do constraints systematically apply where they apparently shouldn’t, or fail to apply where they apparently should? Analyzing evidence from a variety of languages—including English, Finnish, Arabic, Yowlumne Yokuts, Kashaya, Maltese, Dutch, Basque, Tigrinya, Spanish, and Catalan—Paul Kiparsky compares SOT with alternative theories, arguing that it is formally cleaner and makes better sense of a range of empirical phenomena.