Any book is a compromise between the original develop, as does its social and cultural context. aspirations of the author(s) and the realities of New research findings enhance understanding or publication. For this reason reviewers, are often open new avenues of endeavour, which, with in- able to take issue not so much with the substantive ductive reasoning, extend the frontiers of the field. content of a book, but with pragmatic decisions New paradigms emerge, and private and public imposed on authors by this need to compromise. attitudes and values change. In short, a book is an The first edition of this book was no exception, ephemeral entity, providing at best a synoptic for the breadth of its canvas made compromise picture: a particular view of the world which is inevitable if its focus on functioning environmental sooner or later out of date and superseded. The systems was not to be lost. Although, hopefully, it first edition of this book, however, was fortunate has proved to be a successful compromise, several in being a little ahead of its time in anticipating such decisions have been questioned, partly by some of the changes which have occurred since its reviewers, partly by feedback from students and publication. The preface to the first edition stated teachers using the book.