Vagueness, presupposition and truth-value judgements
Jérémy Zehr · HAL (Le Centre pour la Communication Scientifique Directe) · 2014
The aim of my thesis is to give a uniform account of non-bivalent truth-value judgments induced by presuppositional expressions and by vague expression (namely judgments other than "True" or "False"). For example, a presuppositional sentence like 1 below is typically judged neither true nor false in a context where Oscar is not French, and a vague sentence like 2 is also reported as neither true or nor false in a context where Oscar is of an average height. The same holds of a hybrid sentence like 3, combining a vague adjective and a presuppositional expression, in a context where the interlocutor is of an average height:1. Oscar has realized that you are French.2. Oscar is old.3. Oscar has realized that you are old. Abstract: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 propose a system with five totally ordered values, thereby defining three intermediate levels between true and false.After collecting experimental data conflicting with the predictions of this system, I propose a system with four values which is compatible with the experimental results and where the four values are partially ordered along a dimension specific to vagueness and along a dimension specific to presupposition.To get further insights about truth-value judgments specific to vagueness, I conducted another set of experiments (in collaboration with Paul Égré), showing that speakers systematically reject contradictory descriptions of the form "old and young" but that they 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 adjectival antonyms.