This piece of work began life as a doctoral thesis written at the University of Texas between 1976 and 1978. Now after a year in Dublin it is to become a book. Of the many people in the Department of Linguistics at Texas who shaped my interests and who helped me through the writing of the thesis, I must single out Lee Baker, Lauri Karttunen, Bill Ladusaw, Sue Schmerling and Stanley Peters for special gratitude. All of them have provided specific suggestions which have improved this work, but perhaps more .importantly they provided a uniquely stimulating and harmonious environment in which to work, and a demanding set of professional standards to live up to. To Ken Hale lowe a particular debt of gratitude - for two years of encour agement and suggestions, and particularly for a set of detailed comments on an earlier version of the book which led to many changes for the better. I also thank my friends Per-Kristian Halvorsen and Elisabet Engdahl, both of whom took the trouble to provide me with detailed criticisms and comments. In Dublin I am grateful to the School of Celtic Studies of the Institute for Advanced Studies for giving me the opportunity of teaching a seminar on many of the topics covered in the book and of exposing the material to people whose knowledge of the language is unequalled. Donal 6 Baoill and Liam Breatnach have been particularly helpful.