Secular priest, controversialist, and informer; b. Barrow-upon-Humber, Lincolnshire, 1622; d. London, 1707. He entered St. John's College, Cambridge, in 1639 and graduated in 1642. For a short time he was secretary to Thomas Morton, Bishop of Durham, and he then became converted to Catholicism. He entered the English College, Lisbon, in November 1643, was ordained in 1650, and fulfilled various offices in the college. He returned to England in 1652 and became secretary of the English Secular Clergy Chapter. Sergeant hoped for toleration of Catholics on the basis of the acceptance of the Oath of Allegiance and the banishment of the Jesuits from England. He maintained that the Chapter was the organ of ecclesiastical authority for Catholics in England, and that the only alternative to the Chapter was the appointment of a bishop with ordinary jurisdiction. Sergeant's intransigence led to his resignation as secretary of the Chapter in 1667. In 1673 he was in Paris, where he engaged in controversy with Peter talbot, Archbishop of Dublin, who, with the support of John Warner, SJ, had delated some of Sergeant's writings to Rome as being heretical on the subject of the prolegomena fidei.
In common with certain other English and Irish priests who supported the Oath of Allegiance, Sergeant was under "protection" from the English government from about 1671 onward. At the outbreak of the Titus oates plot, October 1678, a special Privy Council order was made restricting him to his house, but in June 1679 he left England for Flanders. There he came in contact with the apostate Rookwood, who introduced him to the English envoy at The Hague, Henry Sidney, as being willing to make a "discovery" concerning the Jesuits and the Plot. In October 1679 Sergeant made his deposition to the Privy Council, which was printed by the Oxford Parliament in March 1681. For this he received a salary from Secret Service funds. In 1681 he wrote to Henry Hyde, Second Earl of Clarendon, offering to act as informer against the Jesuits. In the reign of James II he was secretary to the Duke of Perth, and to the very end of his life he tried to assert his authority over the English Secular Clergy Chapter. His controversial and philosophical writings are voluminous and turgid. Like Kenelm Digby and Thomas white (alias Blacklow), he was one of the few 17th-century English Catholic writers who tried to adapt his epistemology to the new philosophical tendencies of the age. Method to Science (1696) is anti-Cartesian; Solid Philosophy (1697) is an early critique of Locke—Locke's own annotated copy is in St. John's College, Cambridge.
Bibliography: t. cooper, The Dictionary of National Biography from the Earliest Times to 1900, 63 v. (London 1885–1900; reprinted with corrections, 21 v., 1908–09, 1921–22, 1938; supplement 1901–) 17:1189–91. j. gillow, A Literary and Biographical History or Bibliographical Dictionary of the English Catholics from 1534 to the Present time, 5 v. (London–New York 1885–1902 repr. New York 1961) 5:491–498. m. v. hay, The Jesuits and the Popish Plot (London 1934). j. warner, The History of the English Persecution of Catholics and the Presbyterian Plot, tr. j. bligh, ed. t. a. birrel (Publications of the Catholic Record Society 47–48; 1953–55). t. a. birrell, "English Catholics without a Bishop 1655–72," Recusant History 4.4 (1957–58) 142–178.
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