A Simple Logic of Cohesive Group Agency
Nicolas Troquard
TL;DR
The paper develops cohesion networks as formal representations of a group's social fabric, linking subgroups through pro-social behaviors to explain cohesive group agency. It extends the logic of agency with a new successful-assistance modality and a tau-transformation that reduces group-level modalities to network-based, edge-wise components, obtaining a decidable, class-parametrized logic for cohesive action. By defining $E_G\phi$ and $A_G\phi$ through network satisfaction and individual attempts, and by illustrating with the Piano and Peanuts examples, the work provides a principled framework for attributing group responsibility and reasoning about cooperative outcomes in multi-agent settings. The approach has potential implications for AI governance and social-science modeling by enabling rigorous analysis of when and how groups cohesively bring about desired states.
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 prescribed `pro-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 of `successful 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.