The Value of the One Value: Exactly True Logic revisited

In this paper we re-assess the philosophical foundation of Exactly True Logic ( ET L ), a competing variant of First Degree Entailment ( FDE ). In order to do this, we first rebut an argument against it. As the argument appears in an interview with Nuel Belnap himself, one of the fathers of FDE , we believe its provenance to be such that it needs to be taken seriously. We submit, however, that the argument ultimately fails, and that ET L cannot easily be dismissed. We then proceed to give an overview of the research that was inspired by this logic over the last decade, thus providing further motivation for the study of ET L and, more generally, of FDE -related logics that result from semantical analyses alternative to Belnap’s canonical one. We focus, in particular, on philosophical questions that these developments raise.