First ever critical study of Tolkien's little-known essay, which reveals how language invention shaped the creation of Middle-earth and beyond. J.R.R. Tolkien's linguistic invention was a fundamental part of his artistic output, to the extent that later on in life he attributed the existence of his mythology to the desire to give his languages a home and peoples to speak them. An annotated edition of Tolkien's seminal 1930s essay 'A Secret Vice'.