The major perspective we adopt in this book regards a language as a cognitive system which is part of any normal human being’s mental or psychological structure. An alternative to which we shall also give some attention emphasises the social nature of language, for instance studying the relationships between social structure and different dialects or varieties of a language. The cognitive view has been greatly influenced over the past five decades by the ideas of the American linguist and political commentator Noam Chomsky. The central proposal which guides Chomsky’s approach to the study of language is that when we assert that Tom is a speaker of English, we are ascribing to Tom a certain mental structure. This structure is somehow represented in Tom’s brain, so we are also implicitly saying that Tom’s brain is in a certain state. If Clare is also a speaker of English, it is reasonable to suppose that Clare’s linguistic cognitive system is similar to Tom’s. By contrast, Jacques, a speaker of French, has a cognitive system which is different in important respects from those of Tom and Clare, and different again to that of Guo, a speaker of Chinese.

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