What is it for a sentence—or a substantial expression, such as a word or phrase—to have a particular "meaning" in a given language? While it is widely agreed that the meaning of a sentence, phrase, or word must have something to do with the way that the expression is used by speakers of the language, it is not at all obvious how to move from that vague idea to a precise answer to our question. One problem is that utterances of a given sentence might be used to convey all manner of messages, many of which would be far removed from what we intuitively regard as the literal linguistic meaning of the sentence. Any account of meaning in terms of use must find a way to avoid having every innovative or idiosyncratic feature of use registered as an aspect of meaning. There are two ideas about...