Xu, Chao and Wang, Yanjing and Studer, Thomas
Synthese, Volume 198, Pages 1259–1285
Publication year: 2021

Abstract. When we say “I know why he was late”, we know not only the fact that he was late, but also an explanation of this fact. We propose a logical framework of “knowing why” inspired by the existing formal studies on why-questions, scientific explanation, and justification logic. We introduce the $Ky_i$ operator into the language of epistemic logic to express “agent i knows why phi” and propose a Kripke-style semantics of such expressions in terms of knowing an explanation of phi. We obtain two sound and complete axiomatizations w.r.t. two different model classes depending on different assumptions about introspection.