A Generic Approach to Coalition Formation Krzystof Apt, Andreas Witzel Abstract: We propose an abstract approach to coalition formation by focusing on partial preference relations between partitions of a grand coalition. Coalition formation is modelled by means of simple merge and split rules that transform partitions. We identify conditions under which every iteration of these rules yields a unique partition. The main conceptual tool is the notion of a stable partition. The results naturally apply to coalitional TU-games and to some classes of hedonic games.e