Peter Mark Roget created a classed catalogue of words on a small scale in 1805 for his own use as a writer and lecturer. However, it was only after retiring from the duties of Secretary of the Royal Society that he was able to amplify the volume and create the now famous 1852 edition. Since then, Roget's Thesaurus has been updated many times, but Roget's original classification system for the book has stood the test of time and is still used today. George Davidson is a highly experienced editor and lexicographer, and a former senior editor at Chambers Harrap. He edited the 150th anniversary edition of Roget and is currently writing a Pocket Roget Thesaurus. He lives in Edinburgh.