Priestley, Joseph, 1733–1804, English theologian and scientist. He prepared for the Presbyterian ministry and served several churches in England as pastor but gradually rejected orthodox Calvinism and adopted Unitarian views. He settled in London in 1765 and moved to Birmingham some years later. In both cities he became associated with some of the outstanding figures of his day, such as Benjamin Franklin, James Boswell, James Watt, Josiah Wedgwood, and Erasmus Darwin. Priestley's Essay on Government (1768) suggested the idea of "the greatest happiness of the greatest number" to Jeremy Bentham. In 1769 he founded the Theological Repository for critical discussion. In his History of Electricity (1767), he explained the rings (known as Priestley's rings) formed by a discharge upon a metallic surface. His improvements in the manipulation of gases enabled him to investigate the properties of gases and to discover new ones, including sulfur dioxide, ammonia, and what Priestley called "dephlogisticated air," the gas that Lavoisier named oxygen and made the basis of experiments that were the foundation of modern chemistry. Priestley himself, however, failed to realize the importance of his discovery of oxygen.
Priestley's Examination of Scottish Philosophy appeared in 1774; his History of the Corruptions of Christianity, published in 1782, was officially burned in 1785; and his History of Early Opinions concerning Jesus Christ appeared in 1786. In 1790 he wrote two volumes of a General History of the Christian Church to the Fall of the Western Empire, and four volumes of the later history of the church appeared between 1802 and 1803. In the meantime he pursued his scientific and philosophical studies; opposed orthodox doctrines, the government's colonial policy, and slave trade; advocated the repeal of the Test Act and Corporation Act; and carried on a seven-year controversy (1783–90) with the Rev. Samuel Horsley.
Priestley's sympathy with the aims of the French Revolution aroused popular prejudice against him, which led in 1791 to the wrecking of his house and the destruction of his library and scientific apparatus. Priestley emigrated to the United States in 1794 and lived at Northumberland, Pa., for the remainder of his life. He became friendly with many of the nation's founders, forming a particularly close tie with Thomas Jefferson, and continued his chemical experimentation, engaging in a controversy on the phlogiston theory with leading American chemists. Priestley, who was fluent in seven languages, wrote a total of nearly 500 books and pamphlets.
See his letters, ed. by R. E. Schofield (1966); his memoirs (2 vol., 1806, repr. 1970); L. Kieft and B. R. Willeford, Jr., Joseph Priestley: Scientist, Theologian, and Metaphysician (1979); J. J. Huecher, Joseph Priestley and the Idea of Progress (1987); S. Johnson, The Invention of Air (2008); bibliography by R. E. Crook (1966).
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