A Simple Logic of Cohesive Group Agency

Abstract: We propose a structure to represent the social fabric of a group. We call it the cohesion network' of the group. It can be seen as a graph whose vertices are strict subgroups and whose edges indicate a prescribedpro-social behaviour' from one subgroup towards another. In social psychology, pro-social behaviours are building blocks of full-blown cooperation, which we assimilate here with group cohesiveness'. We then define a formal framework to study cohesive group agency. To do so, we simply instantiate pro-social behaviour with the more specific relation ofsuccessful assistance' between acting entities in a group. The relations of assistance within a group at the moment of agency constitute the social fabric of the cohesive group agency. We build our logical theory upon the logic of agency "bringing-it-about". We obtain a family of logics of cohesive group agency, one for every class of cohesion networks.