This book has two main goals: the re-establishment of a rule-based

phonology as a viable alternative to current non-derivational models,

and the rehabilitation of historical evidence as a focus of phonological

theory. Although Lexical Phonology includes several constraints, such

as the Derived Environment Condition and Structure Preservation,

intended to reduce abstractness, previous versions have not typically

exploited these fully. The model of Lexical Phonology presented here

imposes the Derived Environment Condition strictly; introduces a new

constraint on the shape of underlying representations; excludes under-

speci®cation; and suggests an integration of Lexical Phonology with

articulatory phonology. Together, these innovations ensure a substan-

tially more concrete phonology. The constrained model is tested against

a number of well-known processes of English, Scottish and American

accents, including the Vowel Shift Rule, the Scottish Vowel Length

Rule, and [r]-Insertion, and draws interesting distinctions between what

is derivable by rule and what is not. Not only can this Lexical

Phonology model the development of low-level variation to phonolo-

gical rules, and ultimately to dialect differentiation in the underlying

representations; but a knowledge of history also makes apparently

arbitrary synchronic processes quite natural. In short the phonological

past and present explain one another.