LIRa session: 石辰威 Chenwei Shi

Speaker: 石辰威 Chenwei Shi (ILLC, Amsterdam)

Date and Time: Thursday, November 9th 2017, 16:00-17:30

Venue: ILLC Seminar Room F1.15, Science Park 107.

Title: DeGroot Meets Kripke — Group belief as a tendency towards consensus.

Abstract. In this talk, I propose a notion of group belief — potential group belief and study its logic.   What is group belief?  For example,  common belief is a notion of group belief, which is studied a lot in epistemic logic. The notion I will talk about is more in line with what is studied in belief merging and judgement aggregation.  But our perspective is a little different. Rather than aggregation mechanisms, we put focus on the role of the social network and its influence in the forming of the group’s collective belief. In this sense, it is more similar to opinion diffusion.  This is why we start from the DeGroot model, where the social network and its influence on group members are explicitly characterized. The difficulty is that the DeGroot model deals with degree of belief rather than binary or qualitative belief. Our endeavour thus starts with overcoming this difficulty.  After introducing potential group belief, I will show how we can study its logical properties by bringing Kripke semantics into play. Some interesting logical properties emerge, for example, failing to be closed under conjunction. If time permits, I will talk about how to avoid this failure by revising the definition of potential group belief.

This is a joint work with Alexandru Baltag, Sonja Smets and Fenrong Liu.