Peter Mark Roget LRCP FRS FRCP FGS FRAS (UK: /ˈrɒʒeɪ/ US: /roʊˈʒeɪ/;^[1][2] 18 January 1779 – 12 September 1869) was a British physician, natural theologian, lexicographer, and founding secretary of The Portico Library.^[3] He is best known for publishing, in 1852, the Thesaurus of English Words and Phrases, a classified collection of related words (thesaurus). He also read a paper to the Royal Society about a peculiar optical illusion in 1824, which is often regarded as the origin of the persistence of vision theory that was later commonly used to explain apparent motion in film and animation.^[4]

Peter Mark Roget was born in Broad Street, Soho, London, the son of Jean (John) Roget (1751–1783), a Genevan cleric, and Catherine Romilly, the sister of British politician, abolitionist, and legal reformer Sir Samuel Romilly.^[5][6] Following his father's death, the family moved to Edinburgh in 1783 where Roget later studied medicine at the University of Edinburgh, graduating in 1798.^[5] Samuel Romilly, who took on the role of surrogate father to Roget and supported his nephew's education, also introduced him into Whig social circles.^[7]

Roget then attended lectures at London medical schools.^[5] Living in Clifton, Bristol, from 1798 to 1799, he knew Thomas Beddoes and Humphry Davy and frequented the Pneumatic Institute.^[8]

Not making a quick start to a medical career, in 1802 Roget took a position as a tutor to the sons of John Leigh Philips, with whom he began a Grand Tour during the Peace of Amiens, travelling with a friend, Lovell Edgeworth, son of Richard Lovell Edgeworth. When the Peace abruptly ended he was detained as a prisoner in Geneva. He was able to bring his pupils back to England in late 1803, but Edgeworth was held in captivity until Napoleon fell on 6 April 1814.^[5]

With the help of Samuel Romilly, Roget became a private physician to William Petty, 1st Marquess of Lansdowne, who died in 1805. He then succeeded Thomas Percival at Manchester Infirmary and began to lecture on physiology. He moved to London in 1808 and in 1809 became a licentiate of the Royal College of Physicians. After an extended period of dispensary work and lecturing, in particular, at the Russell Institution and Royal Institution, he was taken onto the staff of the Queen Charlotte Hospital in 1817.^[5][7] He also lectured at the London Institution and the Windmill Street School.^[9]

In 1823 Roget and Peter Mere Latham were brought in to investigate disease at Millbank Penitentiary.^[9] In 1828 Roget, with William Thomas Brande and Thomas Telford, submitted a report on London's water supply. In 1834 he became the first Fullerian Professor of Physiology at the Royal Institution. One of those who helped found the University of London in 1837, he was an examiner in physiology there. He gave up medical practice in 1840.^[5]

Roget retired from professional life in 1840, and by 1846 was working on the book that perpetuates his memory today.^[5] It has been claimed that Roget struggled with depression for most of his life, and that the thesaurus arose partly from an effort to battle it.^[10] A biographer stated that his obsession with list-making as a coping mechanism was well established by the time Roget was eight years old.^[11] In 1805, he began to maintain a notebook classification scheme for words, organized by meaning.^[5] During this period he also moved to Manchester, where he became the first secretary of the Portico Library.^[12]

The catalogue of words was first printed in 1852, titled Thesaurus of English Words and Phrases Classified and Arranged so as to Facilitate the Expression of Ideas and Assist in Literary Composition. During Roget's lifetime, the work had twenty-eight printings. After his death, it was revised and expanded by his son, John Lewis Roget (1828–1908), and later by John's son, the engineer Samuel Romilly Roget (1875–1953).^[5][13] Roget's private library was put up for auction in 1870 at Sotheby's and its catalogue has been analyzed.^[14]

Roget was elected a Fellow of the Royal Society in 1815, in recognition of a paper on a slide rule with a loglog scale. He was a secretary of the Society from 1827 to 1848.^[5] On 9 December 1824, Roget presented a paper on a peculiar optical illusion to the Philosophical Transactions, which was published in 1825, as Explanation of an optical deception in the appearance of the spokes of a wheel when seen through vertical apertures.^[15][16] The paper was noted by Michael Faraday and by Joseph Plateau, who both mentioned it in their articles that presented new illusions with apparent motion.^[17][18] It has often been heralded as the basis for the persistence of vision theory, which has for a long time been falsely regarded as the principle causing the perception of motion in animation and film.^[19] In 1834, Roget claimed to have invented "the Phantasmascope or Phenakisticope" in the spring of 1831, a few years before Plateau introduced that first stroboscopic animation device.^[20]

One of the promoters of the Medical and Chirurgical Society of London, which later became the Royal Society of Medicine, Roget was also a founder of the Society for the Diffusion of Useful Knowledge, writing a series of popular manuals for it.^[7] He wrote numerous papers on physiology and health, among them the fifth Bridgewater Treatise, Animal and Vegetable Physiology considered with reference to Natural Theology (1834), and articles for the Encyclopædia Britannica. He was hostile to phrenology, writing against it in a Britannica supplement in 1818, and devoting a two-volume work to it (1838).^[21]

A chess player, in an article in the London and Edinburgh Philosophical Magazine Roget solved the general open knight's tour problem. He composed chess problems, and designed an inexpensive pocket chessboard.^[5][22]

In 1818 Roget was called by the family to the home of Samuel Romilly following the death of his wife, Lady Romilly. Roget's uncle and surrogate father committed suicide by cutting his throat, dying in Roget's presence.^[5]

Canadian writer Keath Fraser published a story, Roget's Thesaurus, in 1982, which is narrated in Roget's voice. He has Roget speak on his wife's death, from cancer.^[27]

Roget also appears in Shelagh Stephenson's An Experiment with an Air Pump, set in 1799, as the only historical character. The play is set in the fictional household of Joseph Fenwick, and Roget is one of Fenwick's assistants.^[28]

A picture-book biography of Roget entitled The Right Word: Roget and His Thesaurus was published by Eerdmans Books in 2014. It was named a Caldecott Honor book for excellence in illustration and won the Sibert Medal for excellence in children's nonfiction.^[29][30]