Longfield, Mountifort (1802–84), economist and lawyer, was second son of the Rev. Mountifort Longfield (d. 1850), JP and vicar of Desert Serges, Co. Cork, of the Anglo-Irish Longfield family of Longueville, near Mallow, Co. Cork, and his first wife, Grace, daughter of William Lysaght of Fort William and Mount North, Co. Cork. At TCD he was a member of the College Historical Society and received a BA as moderator with a gold medal in science (1823). He became a fellow of the college as a ‘jurist’ (1825), and graduated MA (1827) and LLD (1831) there. He was called to the bar at Gray's Inns, London (1828) and to the Irish bar at King's Inns, Dublin (1829). Longfield became deputy professor of feudal and English law at TCD (1832–3) and subsequently its first professor of political economy (1832–6). The chair was established through the efforts of Richard Whately (qv), Oxford economist and newly appointed Church of Ireland archbishop of Dublin. Whately personally selected Longfield for the similarity of their economic and religious views, and the two remained closely linked for the next three decades. In a short space of time, Longfield published his lectures on political economy (1834), on the poor laws (1834), and on commerce and absenteeism (1835). While these and subsequent writings on banking show him to have been largely an advocate of laissez faire economics, he was already suggesting the possibility of state pensions for the aged, a proposition anathema to many classical economists. On currency and banking reform he supported the creation by the state of a monopoly bank of issue to stabilise the money supply and guard against the reckless policies of private joint-stock banks. On the poor laws he accepted that the state had an ethical responsibility to the poor but was anxious that relief would be limited to a level that would not demoralise them by diminishing their incentive to work. He was a critic of absenteeism, arguing that the expenditure abroad of rental income earned in Ireland was a significant factor in holding back the Irish economy.
Longfield resigned the chair when offered the professorship of feudal and English law (1836–84); his successor was Isaac Butt (qv). The remainder of his life was spent in law, especially the law of real property. He was subsequently QC (1842), one of three commissioners under the encumbered estates act (1849), and judge of the landed estates court (1858–67). He was later a bencher of King's Inns (1859) and appointed to the Irish privy council (1867). He took a particular interest in the Irish land question and announced in November 1864 that while fixity of tenure was impracticable he believed that some provision should be made to compensate tenants for improvements to rented property. Like J. S. Mill and J. E. Cairnes (qv), he supported state intervention in landlord-tenant land contracts in Ireland and in a series of essays published in 1870 for the Cobden Club in London put forward a proposal which became known as the ‘Longfield scheme’; this advocated that the tenant be permitted to buy the tenant-right and continuous occupancy of his farm by giving the landlord ten years’ purchase of the rent. This was not incorporated into the 1870 bill, and many commentators regarded this as a lost opportunity of improving the bill. Nevertheless, Longfield played an important role in Irish land reform and assisted in drafting the Irish measures of the first two Gladstone administrations.
Perhaps as a result of the famine and contemporary landlord–tenant tensions, Longfield increasingly supported state intervention in the economy and a more flexible approach to property rights, believing the profit motive was perverting the public good. He stressed that the right to private property in land was not an inviolable right but was justified only as long as it contributed to public welfare. This shift in opinion away from classic laissez faire doctrines was increasingly evident in his later writings. ‘The limits of state interference with the distribution of wealth’ (Stat. Soc. Ire. Jn., xlii (1872)) suggested a number of government initiatives: worker cooperatives and state-supported clubhouses; pensions for the blind, deaf, and aged; free state education, medical care, and homes for the incurably ill; housing regulation and state parks. According to his biographer, ‘Longfield's great contribution to economics was the consistency with which he used economic analysis to evaluate proposed legislative reforms' (Moss, 181).
Longfield was also active in the Social Science Congress and a founding member of the Statistical Society (1847–8), later the Statistical and Social Inquiry Society of Ireland. He served as vice-president to Whately, and on Whately's death, held the presidency (1863–7). Longfield was also a commissioner of education (1853) and assessor of the general synod of the Church of Ireland. In later years, he wrote a pamphlet on pensions for the clergy (1870) and a book on the mathematics of finance (1872), before entering semi-retirement in 1874. Longfield married (1845) Elizabeth Penelope, daughter of Andrew Armstrong. She predeceased him (1882) and he died 21 November 1884 at 47 Fitzwilliam Square, Dublin. His nine brothers and half-brothers included an MP (Robert), two Church of Ireland ministers (Richard and George, FTCD), a JP (William), and a lieutenant-colonel in the army (Foster). Of his five sisters, his youngest half-sister, Frances Patience, married their cousin, Gen. John Longfield, CB, of Kilcoleman, Bandon, Co. Cork.