Vague, Présupposition et Jugements de Valeur de Vérité

Abstract

This thesis aims to jointly account for the non-bivalent truth value judgments, namely judgments which neither correspond to “True” nor to “False”, that are triggered by presuppositional sentences (like 1 in a context where Oscar is not French), vague sentences (like 2 in a context where Oscar is of an average age) or even hybrid sentences (like 3 in the same context).1.Oscar has realized that you are French.2.Oscar is old.3.Oscar has realized that you are old.Drawing on systems defining three logical values (true, false and other) and discussed both in the literature on vagueness and in the literature on presupposition, I develop a system with five totally ordered values, which thus defines three intermediate levels between true and false. After collecting experimental data conflicting with the predictions of this system, I propose a system with four partially ordered values, which is compatible with the experimental results and which defines vagueness and presupposition as entering in relation with truth along distinct specific dimensions.In parallel, I conducted an experiment in collaboration with Paul Égré, which shows that speakers systematically reject contradictory descriptions of the form “old and young” but can accept contradictory descriptions of the form “neither old nor young”, “neither old nor not old” and “old and not old”. These results echo the idea that vague sentences like 1 can be judged “Neither true nor false” but also “True and false”, and allow us to discriminate between two competing theories of antonyms.