Something that a theorist of language may hope to understand — or to understand better as the result of his theorizing — is the notion of meaning, at least as it applies to sentences, words, and other linguistic expressions. As we try to attain such an improved understanding, Strawson's warning is salutary. As he says, we cannot hope to understand the notion of an expression's meaning unless we enjoy at least a basic understanding of the nature of human speech (and writing). For our sentences and words have meaning only in so far as they could be used in speech or writing. He is also right to say that we cannot hope to understand speech unless we take account of the aim of communication. Some speech, of course, has no communicative purpose.