ABSTRACT
This chapter introduces the book, in purpose and structure. It proposes that a book of reprinted articles, in the parts Theory, Empirical Work, and Testing and Assessment can make a distinctive contribution, especially since each section contains relatively early and relatively late reprinted articles. The chapter outlines the context for the writing of the individual reprinted chapters and why they were chosen for inclusion. It also explains what the reflections chapters which appear at the end of each section try to accomplish, by trying to establish what progress has been made in each area of enquiry, and by discussing the area in question with a wider perspective.
