Knowles, James Sheridan (1784–1862), playwright, actor, and teacher, was born 12 May 1784 in Anne Street, Cork, the son of schoolteacher and lexicographer James Knowles (qv), a first cousin of Richard Brinsley Sheridan (qv), and his wife, Jane Daunt (née Peace, d. 1800), a young widow connected to the Dublin Le Fanu family. He moved with his family to London in 1793 where his precocious literary talents soon became apparent when he published his first work, a ballad entitled ‘The Welch harper’, when he was twelve years old. He formed a close friendship with the English critic and essayist William Hazlitt, a family friend, who became something of a second father to the young Knowles, encouraging his literary ambitions and introducing him to Samuel Taylor Coleridge and Charles Lamb.
In 1800 Knowles's mother died; finding relations with his new stepmother (a Miss Maxwell) difficult, Knowles left home. Over the next few years he worked for brief stints in the stamp office and in the army (1804–5), before studying medicine at the University of Aberdeen, where he graduated MD. He soon abandoned the medical profession for the theatre, making his stage debut in Bath, and subsequently playing Hamlet at the Crow Street theatre, Dublin (1808). He next worked with William Smithson's company in Wexford, where he met the Scottish actress Maria Charteris, whom he married in October 1809. They worked together in Andrew Cherry's company at Waterford, where Knowles became friendly with Edmund Kean, then an obscure actor. Knowles wrote his first mature play, ‘Leo, or, The gypsy’, successfully produced at Waterford in 1810, as a vehicle for Kean. In the same year he published A collection of poems on various subjects. He spent the next season working in Swansea, where his son – the first of his ten children – was born.
Knowles moved to Belfast where, at the request of his manager, he wrote and performed in a popular melodrama entitled ‘Brian Boroihme’ (March 1812), followed by the well-received tragedy ‘Caius Gracchus’, first played by Talbot's Company in Belfast, 1815. However, his burgeoning writing career proved insufficient to meet the needs of a growing family, and he supplemented his income by teaching, opening his own school in Belfast where he taught grammar, composition, and recitation. In 1813 he was offered a position at the Belfast Academical Institution but declined in favour of his father and worked there as his assistant. This arrangement proved so acrimonious, however, that he moved to Glasgow in 1816, where he opened another school, which he ran for twelve years.
His next play, ‘Virginius’, established his reputation as a major dramatist, and typified his signature blend of historical settings and Victorian sensibilities – particularly the contemporary taste for domestic themes – which proved immensely popular with critics and audiences alike. Described by Hazlitt as ‘the best acting tragedy that has been produced on the modern stage’ (Hazlitt, 256), ‘Virginius’ was first performed at the Theatre Royal, Glasgow, in April 1820, before its successful London debut at Covent Garden on 17 May 1820 with William Charles Macready in the title role. After a reworked version of ‘Caius Gracchus’ (Covent Garden, 1823), and an adaptation of Massinger's ‘The fatal dowry’, his next original play, ‘William Tell’, opened at Drury Lane on 11 May 1825, with Macready leading the cast in what was to become one of his most acclaimed dramatic roles. Knowles was pronounced by Hazlitt to be ‘the first tragic writer of the age’ (Hazlitt, 257), yet his finances remained precarious and he pursued collateral literary projects to supplement his income. He edited a Glasgow paper (the liberal Free Press) in 1823–4, taught, and gave public lectures on oratory and drama. In the mid-1820s he edited and published The elocutionist, an anthology of texts for declamation that became a well-known textbook (reaching its 28th edition in 1883).
Knowles's next two plays, ‘The beggar's daughter of Bethnal Green’ (Drury Lane, 1828) and ‘Alfred the Great’ (Drury Lane, 1831), met with mixed success, but ‘The hunchback’ (5 April 1832, Covent Garden) was a triumph, and became his most popular play; Knowles returned to the stage to take the part of Master Walton, and from that time he acted regularly until 1843, though his talents were regarded as unremarkable. He continued to write prolifically – ‘The wife’ enjoyed a successful run at Covent Garden in 1832 – and in 1834 returned to Ireland, playing in Cork, Limerick, and Clonmel. A tour of America followed, where his reputation as the leading dramatist of his time was already well-established, ‘Brian Boroihme’ having been successfully produced in New York in the late 1820s. He returned to England and wrote ‘The love chase’ (10 September 1837, Haymarket), a deftly plotted comedy which proved to be his last dramatic work of any significance.
In 1841 Maria Charteris died, and the following year Knowles married a young actress named Emma Elphinstone. His plays were unable to maintain the critical and commercial success of his earlier work, and in 1844 he left the theatre to become an evangelical baptist preacher. He was ordained a minister in 1845, and engaged in religious controversy, publishing several polemical works attacking catholicism, particularly Cardinal Wiseman and the Oxford Movement (Rock of Rome, 1849; The idol demolished by its own priest, 1851). He also published two novels, Fortescue (1846) and George Lovell (1847), as well as the theological commentary The gospel attributed to Matthew (1855). In 1848 he was awarded a civil list pension of £200. His later years were spent in Torquay, where he died 30 November 1862. He was buried in the Glasgow necropolis. His son, Richard Brinsley, a writer and journalist, privately printed his father's Life; and several anthologies of his works and public lectures appeared posthumously.
Collections of Knowles's correspondence are held by the Bodleian Library, Oxford, the Huntington Library, California, the Royal Society, London, and the National Library of Scotland. Four likenesses are in the National Portrait Gallery, London, including a portrait by Wilhelm Trautschold (oils, exh. 1849), and a mezzotint of Knowles as St Pierre in ‘The wife’ (1833) by Theodore Francis. A lithograph by Daniel Maclise (qv) (1873) is in the British Museum, London.