Why is ordinary language vague? We argue that in contexts in which a cooperative speaker is not perfectly informed about the world, the use of vague expressions can offer an optimal tradeoff between truthfulness (Gricean Quality) and informativeness (Gricean Quantity). Focusing on expressions of approximation such as “around”, which are semantically vague, we show that they allow the speaker to convey indirect probabilistic information, in a way that can give the listener a more accurate representation of the information available to the speaker than any more precise expression would (intervals of the form “between”). That is, vague sentences can be more informative than their precise counterparts. We give a probabilistic treatment of the interpretation of “around”, and offer a model for the interpretation and use of “around”-statements within the Rational Speech Act (RSA) framework. In our account the shape of the speaker’s distribution matters in ways not predicted by the Lexical Uncertainty model standardly used in the RSA framework for vague predicates. We use our approach to draw further lessons concerning the semantic flexibility of vague expressions and their irreducibility to more precise meanings.

为什么普通语言含糊不清？我们认为，在合作发言者对世界没有完全了解的情况下，使用模糊表达可以在真实性（格莱斯质量）和信息性（格莱斯数量）之间提供最佳权衡。重点关注语义上模糊的近似表达，例如“around”，我们表明它们允许说话者传达间接概率信息，其方式可以让听者比任何其他方式更准确地表示说话者可用的信息。更精确的表达会（“之间”形式的间隔）。也就是说，模糊的句子比精确的句子能提供更多的信息。我们对“around”的解释进行了概率处理，并提供了在理性言语行为（RSA）框架内解释和使用“around”语句的模型。在我们的解释中，说话者分布的形状并不通过 RSA 框架中标准用于模糊谓词的词汇不确定性模型来预测。我们使用我们的方法来进一步吸取关于模糊表达的语义灵活性及其不可还原为更精确含义的教训。