The natural point at which to begin a discussion of eighteenth-century theories of language is John Locke's 1690 Essay concerning Human Understanding. Virtually every theorist of language and literature over the next century owed something to Book 3 in Locke's Essay, ‘Of Words’. Locke's influence was not, however, to popularize any single doctrine. There were, in fact, two major interpretations of Locke's theory of language, each leading to a quite different conception of its nature and history. The first interpretation looked no deeper than Locke's explicit statements that words were merely arbitrary ‘signs’ of ideas. The second interpretation took inspiration from Locke's unclear but challenging suggestions that words were much more than outward signs, but had a fundamental role in the formation of ideas and their organization in rational thought. These provocative insights into the mental function of language led to the theories of Vico, Condillac, Rousseau, Herder and other philosophers of the mid- and late eighteenth century. These authors would argue that the history of literature had been closely connected with the joint evolution of language and reason.

The ‘arbitrary sign’ and its literary implications

Locke's name is now closely associated with the doctrine that words ‘signify only Men's peculiar Ideas, and that by a perfectly arbitrary Imposition’. Impelled by their natural sociability, argued Locke, the first humans invented ‘external sensible Signs’ to communicate their ‘invisible Ideas’ to others. Locke's insistence that words refer only to ideas in the mind of the speaker, and not to ‘things’ in the world, corrected the habit of many seventeenth-century grammarians and philosophers of using the terms ‘idea’ and ‘thing’ almost interchangeably: Locke's admirers were more careful to specify that words referred only to thoughts in the mind of the speaker, and not to physical objects.