This book represents in the ?rst place the desire of the authors of the various contributions to enter a discussion about the research landscape of prese- day fundamental theoretical physics. It documents their attempt, out of their highly specialized scienti?c positions, to ?nd a way of communicating about methods, achievements, and promises of the di?erent approacheswhich shape the development of this ?eld. It is therefore also an attempt to bring out the connections between these approaches, and present them not as disjoint ventures but rather as facets of a common quest for understanding. Whether in competition to each other or in collaboration, the ‘many-fold ways’ of contemporary physics are characterized by a number of exciting ?ndings (and questions) which appear more and more interrelated. Moreover, in the historical development of science, the steadily arriving new empi- cal information partly supports, partly contradicts the existing theories, and partly brings forth unexpected results forcing a total reorientationupon us. If we are lucky, the beginning of this century may prove to be as grand as that of the last one. Itisnotaneasytaskinasituationsomuchinmovementandinwhich variousapproachesstriveforcompletion,topromoteaconstructiveinteraction between these and to achieve a level of mutual understanding on which such an interaction can be fruitful. Nearly all of the authors contributing to this book have been participating in a working group dedicated exactly to this task; this group met in many sessions over several years. This book is to a large extent the result of these discussions.
