Roget described his thesaurus in the foreword to the first edition:

It is now nearly fifty years since I first projected a system of verbal classification similar to that on which the present work is founded. Conceiving that such a compilation might help to supply my own deficiencies, I had, in the year 1805, completed a classed catalogue of words on a small scale, but on the same principle, and nearly in the same form, as the Thesaurus now published.Roget's Thesaurus is a widely used English-language thesaurus, created in 1805 by Peter Mark Roget (1779–1869), British physician, natural theologian and lexicographer. It was released to the public on 29 April 1852.[1] The original edition had 15,000 words, and each new edition has been larger.[2] Roget was inspired by the Utilitarian teachings of Jeremy Bentham and wished to help "those who are painfully groping their way and struggling with the difficulties of composition [...] this work processes to hold out a helping hand".[3] The Karpeles Library Museum houses the original manuscript in its collection.