This dissertation addresses the broad question about how phonology and phonetics are interrelated, specifically how phonetic language changes, which gradually alter the phonetics of speech sounds, affect the phonological system of the language, and vice versa. Some questions I address are:(i) What aspects of speakers' knowledge of their language are changing during a phonetic change?(ii) What is the relative timing of a phonetic change and phonological reanalysis?(iii) Can a modular feed-forward model of phonology and phonetics account of the observed patterns of phonetic change?(iv) What are the consequences of my results for theories of phonology, phonetics, and language acquisition?(v) What unique insight into the answers to these questions can the study of language change in progress give us over other methodologies?