The theory of practical rationality does not belong to one academic discipline alone. There are quite divergent philosophical, economical, sociological, psychological and politological contributions. Sometimes the disciplinary boundaries impede theoretical progress. On the other hand it is an indication for the high complexity of the subject that so many divergent paradigms compete with one another, or - what is worse - live separately in a kind of splendid isolation. Decision theory in the broader sense, embracing the theory of games and collective choice theory, can help to understand practical reason in philosophical analysis. But there are interesting aspects which cannot be dealt with adequately within a