Seminário de Lógica Matemática

One, and Only One

Sala 6.2.33, FCUL, Lisboa

Por Elia Zardini (Universidade de Lisboa).

Abstract: Standard non-classical (i.e. non-substructural) solutions to the semantic paradoxes of truth deny either the law of excluded middle or the law of non-contradiction; in so doing, they either reject both the truth of a paradoxical sentence and its falsity or accept both the truth of a paradoxical sentence and its falsity. In this sense, both kinds of solutions agree that paradoxical sentences are inconsistent—that such sentences cannot coherently be assigned one and only one truth value. This pattern extends from the semantic paradoxes of truth to the semantic paradoxes of reference: when faced with at least certain particularly recalcitrant paradoxes of naive reference, both kinds of solutions are forced to claim that the paradoxical singular terms in question are inconsistent—that they cannot coherently be assigned one and only one referent. I’ll argue that, contrary to what both kinds of solutions require, under plausible assumptions paradoxical singular terms can be constructed that are forced to refer to a unique object. By considering these and other more traditional paradoxes, I’ll then show how my favoured non-contractive solution to the semantic paradoxes, which generally treats paradoxical entities as consistent rather than as inconsistent, can be so deployed as to offer a unified solution to the semantic paradoxes of truth and to those of reference and definability.

16h00
CMAFcIO - Centro de Matemática, Aplicações Fundamentais e Investigação Operacional