Lying and Vagueness

Vagueness is a double-edged sword in relation to lying and truthfulness. In situations in which a cooperative speaker is uncertain about the world, vagueness offers a resource for truthfulness: it avoids one’s having to commit oneself to more precise utterances that would be either false or unjustifiably true, and it is arguably an optimal solution to satisfy the Gricean maxims of Quality and Quantity. In situations in which a non-cooperative speaker is well-informed about the world, on the other hand, vagueness can be a deceptive mechanism. We distinguish two cases of that sort: cases in which the speaker is deliberately imprecise in order to hide information from the hearer; and cases in which the speaker exploits the semantic indeterminacy of vague predicates to produce utterances that are true in one sense, but false in another. Should such utterances, which we call half-truths, be considered lies? The answer, we argue, depends on the context: the lack of unequivocal truth is not always sufficient to declare falsity.