This series of HANDBOOKS OF LINGUISTICS AND COMMUNICATION SCIENCE is designed to illuminate a field which not only includes general linguistics and the study of linguistics as applied to specific languages, but also covers those more recent areas which have developed from the increasing body of research into the manifold forms of communicative action and interaction. For "classic" linguistics there appears to be a need for a review of the state of the art which will provide a reference base for the rapid advances in research undertaken from a variety of theoretical standpoints, while in the more recent branches of communication science the handbooks will give researchers both an overview and orientation. To attain these objectives, the series aims for a standard comparable to that of the leading handbooks in other disciplines, and to this end strives for comprehensiveness, theoretical explicitness, reliable documentation of data and findings, and up-to-date methodology. The editors, both of the series and of the individual volumes, and the individual contributors, are committed to this aim. The language of publication is English. The main aim of the series is to provide an appropriate account of the state of the art in the various areas of linguistics and communication science covered by each of the various handbooks; however no inflexible pre-set limits will is imposed on the scope of each volume. The series is open-ended, and can thus take account of further developments in the field. This conception, coupled with the necessity of allowing adequate time for each volume to be prepared with the necessary care, means that there is no set time-table for the publication of the whole series. Each volume is a self-contained work, complete in itself. The order in which the handbooks are published does not imply any rank ordering, but is determined by the way in which the series is organized; the editors of the whole series enlist a competent editor for each individual volume. Once the principal editor for a volume has been found, he or she then has a completely free hand in the choice of co-editors and contributors. The editors plan each volume independently of the others, being governed only by general formal principles. The series editors only intervene where questions of delineation between individual volumes are concerned. It is felt that this (modus operandi) is best suited to achieving the objectives of the series, namely to give a competent account of the present state of knowledge and of the perception of the problems in the area covered by each volume. To discuss your handbook idea or submit a proposal, please contact Birgit Sievert.

Classifying objects --- thus collecting them into classes --- is an operation both fundamental and common in everyday life as well as in scientific endeavours. Logic, philosophy, mathematics and computer science analyse this activity by means of such notions as class', set', and type'. Furthermore, according to the so-called logical (or naive) conception of classes," these notions are related to the notion concept' in that classes are considered extensions' of concepts. This relationship, however, is a delicate one --- as we have learned from the paradoxes of class theory. The contributions to this volume shed new light both on concepts and classes and their delicate relationship. New and original approaches to these issues (e.g., map theory, epsilon-sets, intensional type theory, AFA set theory) are presented and discussed in the broader context of their application to problems from informatics and linguistics. The focus is on such matters as unrestrictive comprehension, extensionality, the relationship between the notions of concept, class and extension, and on unfounded (circular and infinitely descending) patterns of elementhood. These and related problems have always played a role in the development of set theory and have always delivered motivation for the development of unorthodox views and theories. This is also demonstrated in this volume by contributions dealing with the history of Zermelo's axiomatization of set theory and Ackermann's class theory with unrestrictive comprehension, respectively. The contributions of this volume are based on the presentation at a Workshop on Alternative Set Theories --- Alternatives to Set Theory" held at the University of Southern Denmark in2006.