Written by the world-renowned pioneer in the field of modern sociolinguistics, this three-volume set examines the historical, social, cognitive, and cultural factors responsible for linguistic change. Presents the results of several decades of inquiry into the social origins and motivation of linguistic changeDevelops the general principles of linguistic change that form the foundations of historical linguistics, dialectology and sociolinguisticsIncludes the first complete report on the Philadelphia project designed to establish the social location of the leaders of linguistic changeDocuments the rapid changes in progress in the cities of America and EnglandA newly-complete trilogy that has shaped the course of variationist sociolinguistic inquiry