This unique book provides an introductory overview of modern theoretical linguistics which manages to be both accessible and humorous without sacrificing either scholarship of insight. In a series of magisterial vignettes Smith emphasizes the perennial necessity of appealing to linguistic theory if we are to gain any real understanding of the phenomena of language. However profound or however trivial the questions we raise and try answer - What exactly does one have to know to count as a speaker of a language? What would it mean for a language to have no vowels? Why do little children call lorries 'lollies'? Precisely what with this sentence is wrong? - we need to recourse to a theory even to make them coherent. In particular, the author argues that we can find solutions to our puzzles, and explanations for these phenomena, if we exploit on the one hand Chomsky's theory of Generative Grammar, and on the other Sperber and Wilson's theory of Relevance.