of papers attempt to challenge the rationality hypothesis head on, at least in its more orthodox formulation. The main purpose of this Handbook is to make more widely available some recent developments in the area. Yet we are well aware that the final chapter of a handbook like this can never be written as long as the area of research remains active, as is certainly the case with utility theory. The editors originally selected a list of topics that seemed ripe enough at the time that the book was planned. Then they invited contributions from researchers whose work had come to their attention. So the list of topics and contributors is largely the editors' responsibility, although some potential con­ tributors did decline our invitation. Each chapter has also been refereed, and often significantly revised in the light of the referees' remarks.