LIRa session: Niccolò Rossi

Speaker: Niccolò Rossi (ILLC, University of Amsterdam)

Date and Time: Thursday, May 25th 2023, 16:30-18:00

Venue: ILLC seminar room F3.20 in Science Park 107 and online.

Title: Disjunctions, topics and grounds

Abstract. If Andrea knows that Biden won the last presidential election, they also know that either Biden won the last presidential election, or Biden is a reptilian. This is the response that epistemic logics based on standard Kripke relational semantics provide, which is consistent with the fact that minimally rational agents can perform disjunction introduction. This is not the case in topic-sensitive semantics though. Andrea might not grasp the concept of ‘reptilian’, and therefore not be able to know any proposition dealing with reptilians. I argue that this requirement is too strong. I keep the idea that topic-grasping is crucial for knowledge, but I weaken the requirement: only grasping some ‘minimal topics’ of a proposition is needed. I use a theory of logical grounding (Correia, 2014) in order to define which are the minimal grounds of a proposition and define a minimal topic as the topic of a minimal ground. Once this is done, I propose a semantic clause for knowledge that maintains the good features of topic-sensitive semantics while improving its treatment of disjunction. Doing so, I exploit the concept of logical grounding in order to define the minimal parts of a proposition which are relevant truth-wise and topic-wise for the knowledge of such a proposition.