Serialism and Opacity in Phonological Theory

Opacity is a natural language phenomenon where a phonological process is rendered non-surface-true by virtue of its interaction with other processes. Phonologists have long been fascinated with opaque generalizations both from a typological standpoint (What kinds of non-surface-true generalizations are found?) and a theoretical one (Which formal tools permit an analysis of opacity?). This review aims to (a) discuss the breadth of non-surface-true generalizations in light of phonologists (often implicit) working definitions of opacity and (b) address opacity as a flashpoint in one of the larger debates in generative phonology, between the rule-based serial approach of Chomsky & Halle's Sound Pattern of English and constraint-based parallel Optimality Theory. A conclusion offered here is that the well-known problems Optimality Theory faces with some kinds of opacity are due not to its lack of serialism but to the fact that such processes are input-motivated rather than output-motivated.