In 1852 Peter Mark Roget eclipsed a rich tradition of topically based dictionaries with the publication of his Thesaurus of English Words and Phrases, Classified and Arranged so as to Facilitate the Expression of Ideas. Based on intuition as much as on specific linguistic principles Roget's book has been a bestseller ever since and is one of the most widely-used reference works ever published. In this book Werner Hüllen gives the first history of its genesis and publication, and investigates the principles of its structural design. The author opens with an account of Roget's life and his background in natural science. He then charts the parallel histories of dictionaries of synonyms and concepts within the general context of lexicography. Synonymy, he argues, is a necessary feature of languages without which communication would be impossible. He traces its theory and practice from Plato to the emergence of French and English synonym dictionaries in the seventeenth century. Roget's was the first such book to be arranged by topic and the first to encompass the semantic network of the entire language. The author examines the manner and method of its compilation, the practical outcomes of the traditions on which it was based, and the ways in which the Thesaurus reflects and reveals Roget's beliefs and background. A History of Roget's Thesaurus will interest students and scholars of linguistics, semantics, and lexicography, as well as anyone wishing to know more about a great literary achievement and an astonishing publishing phenomenon.