This innovative and ground-breaking study explores the complex relationship between linguistic theory and literature during the Romantic period. Several topics in eighteenth-century linguistics are discussed, and the philological interests of figures such as William Godwin, Leigh Hunt, Percy Shelley, Samuel Taylor Coleridge, and Thomas De Quincey are considered. However, it is William Hazlitt's writings about natural language and linguistic theory that provide the central focus, and several crucial issues are considered. In particular, Hazlitt's ambivalent response to the philosophical grammar movement and to the linguistic theorising of John Horne Tooke is revealed in its true complexity, while his views concerning the 'familiar style' are provocatively reinterpreted in the context of the grammar textbook and belletristic rhetoric traditions. In addition, it is shown that Hazlitt's literary criticism was profoundly influenced by his understanding of linguistic theory, an aspect of his work that has been largely ignored in the past.