Joseph Priestley

• 1. Introduction

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  Joseph Priestley was born on the 24th of March 1733 in Birstall, near Batley, in the West Riding of Yorkshire, into a family of English Dissenters who refused to conform to the Church of England. By the time he died on the 6th of February 1804, he had published more than 150 works, isolated oxygen, invented carbonated water, helped found British Unitarianism, and influenced the political philosophy of Jeremy Bentham, John Stuart Mill, and Thomas Jefferson. He was burned in effigy, chased from his home by a mob, and eventually forced to flee to America. Yet for all of that, he never stopped believing that the natural world and Christian faith pointed in the same direction. How did a finisher of cloth's son from Yorkshire become one of the most consequential and controversial figures of the Enlightenment? The answers involve gunpowder, mice, a brewery next door, a French chemist who disagreed with everything Priestley thought he had proved, and a mob that burned his house to the ground on a summer night in 1791.

• 2. A Mind Formed by Dissent

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  At the age of four, Priestley could flawlessly recite all 107 questions and answers of the Westminster Shorter Catechism. His aunt Sarah Keighley, who raised him at the Old Hall in Heckmondwike after his mother died and his father remarried, intended him for the ministry and sought the best education available for him.

  Around 1749, Priestley fell gravely ill and believed he was dying. Raised as a devout Calvinist, he feared he lacked the conversion experience required for salvation. That spiritual crisis loosened his grip on orthodox Calvinist doctrine. He came to reject election and embrace universal salvation, a shift so alarming to his home congregation at the Independent Upper Chapel of Heckmondwike that they refused him full membership. The illness also left him with a permanent stutter that made a career in ministry feel impossible at the time.

  In preparation for working in trade in Lisbon, Priestley studied French, Italian, German, Aramaic, and Arabic. He was tutored by the Reverend George Haggerstone, who introduced him to higher mathematics, natural philosophy, logic, and metaphysics through the works of Isaac Watts, Willem 's Gravesande, and John Locke. That foundation pulled him back toward theology rather than commerce, and in 1752 he enrolled at Daventry Academy in Northamptonshire, a Dissenting institution where his prior reading was so extensive that he was permitted to skip the first two years of coursework.

  The book that shaped him most at Daventry, he later wrote, was David Hartley's Observations on Man (1749), save the Bible itself. Hartley's treatise argued that both religious and moral facts could be scientifically proven, a goal that would occupy Priestley for the rest of his life. By his third year at Daventry, he had committed himself to the ministry, calling it "the noblest of all professions".

• 3. Educator, Grammarian, Historian

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  Robert Schofield, Priestley's major modern biographer, describes his first ministry in 1755 at a Dissenting parish in Needham Market, Suffolk, as a "mistake" for both Priestley and the congregation. The rural flock wanted tradition; Priestley wanted theological debate. Attendance and donations dropped as his heterodox views became clear, and when local families refused to send their children to the school he proposed, he turned to scientific lectures instead. In 1758 he moved to Nantwich, Cheshire, where the congregation was more tolerant and the school he established actually succeeded.

  Appalled by the quality of available English grammar books, Priestley wrote his own: The Rudiments of English Grammar, published in 1761. His effort to separate English grammar from Latin grammar led 20th-century scholars to call him "one of the great grammarians of his time".

  In 1761, Warrington Academy hired him as a tutor of modern languages and rhetoric, though he would have preferred mathematics and natural philosophy. At Warrington he befriended the doctor and writer John Aikin, Aikin's sister Anna Laetitia Aikin, and the potter and businessman Josiah Wedgwood, who would later create a medallion of Priestley in cream-on-blue jasperware. On the 23rd of June 1762, Priestley married Mary Wilkinson of Wrexham, of whom he wrote that she was "a woman of an excellent understanding, much improved by reading, of great fortitude and strength of mind."

  At Warrington, Priestley argued that education should anticipate students' future practical needs. He recommended modern languages over classical ones, and modern history over ancient. He also promoted the education of middle-class women, which was unusual for the time. Some scholars of education have placed him as the most important English writer on education between the 17th-century John Locke and the 19th-century Herbert Spencer.

  His Lectures on History and General Policy was used by institutions including New College at Hackney, Brown, Princeton, Yale, and Cambridge. The two visual timelines he designed to accompany the lectures have been described as the most influential timelines published in the 18th century. The trustees of Warrington were sufficiently impressed that they arranged for the University of Edinburgh to grant him a Doctor of Law degree in 1764.

• 4. Electricity, Oxygen, and Carbonated Water

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  Benjamin Franklin, visiting Britain, encouraged Priestley to conduct the experiments he wanted to describe in a history of electricity. In 1767, the resulting 700-page History and Present State of Electricity was published to positive reviews. Its first half chronicled the study of electricity to 1766; its more influential second half described contemporary theory and proposed directions for future research. Priestley also used the book to argue that scientists should present all reasoning in their discovery path, including false leads and mistakes, a stance that contrasted sharply with Newton's proof-like style.

  In that history Priestley reported several of his own findings. He showed that charcoal and other substances could conduct electricity, overturning what he called "one of the earliest and universally received maxims of electricity," that only water and metals were conductors. Based on experiments with charged spheres, he was among the first to propose that electrical force followed an inverse-square law similar to Newton's law of universal gravitation. He did not develop the idea further, and the general law was formally stated by the French physicist Charles-Augustin de Coulomb in the 1780s. His observation of "a current of real air" between two electrified points later drew the attention of both Michael Faraday and James Clerk Maxwell. Alessandro Volta, William Herschel, and Henry Cavendish all relied on Priestley's history; it remained the standard text on the subject for over a century.

  In August 1774, working in Calne, he isolated an "air" that seemed completely new, but left on a European tour with Lord Shelburne before he could investigate. While in Paris, he replicated the experiment for others, including the French chemist Antoine Lavoisier. Back in Britain, he continued the experiments at Bowood House, calling the new substance "dephlogisticated air." He first tested it on mice, who survived far longer than expected in a sealed vessel, then breathed it himself, writing that it was "five or six times better than common air for the purpose of respiration, inflammation." He had isolated oxygen.

  Also in 1767, after devising a method to infuse water with carbon dioxide from a neighbouring brewery in Leeds, he invented carbonated water. He provided the crew of James Cook's second voyage to the South Seas with a method for making it, incorrectly speculating it might cure scurvy. He did not pursue the commercial potential. Others, including J. J. Schweppe, made fortunes from it. Schweppes has since called Priestley "the father of our industry." In 1773, the Royal Society recognised his contributions to natural philosophy by awarding him the Copley Medal.

• 5. Phlogiston and the Limits of Revolution

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  Priestley discovered oxygen but never accepted what it meant. That paradox sits at the centre of his scientific life. Antoine Lavoisier took Priestley's own experimental data and built a new chemistry from them, one grounded in the conservation of mass and organised around elements and compounds. Priestley refused to follow.

  In Birmingham, where he had joined the Lunar Society alongside the manufacturer Matthew Boulton, the engineer James Watt, and the botanist and geologist William Withering, Priestley published papers attempting to refute Lavoisier's challenges. He and other Lunar Society members argued that the new French system was too expensive, too difficult to test, and unnecessarily complex. Where Lavoisier counted mass, Priestley preferred to observe qualitative changes in heat, colour, and volume. He tested "airs" for their solubility in water, their effect on flame, their behaviour with acid and nitric oxide.

  By 1789, when Lavoisier published his Traité Élémentaire de Chimie, the new chemistry had taken hold. Priestley continued to resist. Schofield's explanation is blunt: "Priestley was never a chemist; in a modern, and even a Lavoisierian, sense, he was never a scientist. He was a natural philosopher, concerned with the economy of nature." Historian of science John McEvoy offers a complementary reading: Priestley's view of nature as coextensive with God, and his emphasis on facts over hypotheses, led him to reject a system built on abstractions. McEvoy argues that "Priestley's isolated and lonely opposition to the oxygen theory was a measure of his passionate concern for the principles of intellectual freedom, epistemic equality and critical inquiry."

  The 19th-century French naturalist George Cuvier captured the irony in his eulogy of Priestley, calling him "the father of modern chemistry who never acknowledged his daughter." Priestley himself, in the last volume of Experiments and Observations, declared that his most valuable works were his theological ones, superior in "dignity and importance" to all the chemistry.

• 6. Political Philosopher and Religious Radical

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  His Essay on the First Principles of Government, published in 1768, is now considered an early work of modern liberal political theory. It distinguished political rights from civil rights with unusual precision, argued for expansive civil liberties, and maintained that education and religion were matters of private conscience that the state had no right to administer. Jeremy Bentham, John Stuart Mill, and Herbert Spencer later drew on Priestley's metaphysical works as primary sources for utilitarianism.

  Priestley also picked direct fights. When the legal theorist William Blackstone's Commentaries on the Laws of England declared that dissent from the Church of England was a crime, Priestley published Remarks on Dr. Blackstone's Commentaries (1769), correcting Blackstone's interpretation of the law, his grammar, and his history. Blackstone, chastened, rephrased the offending passages in later editions and removed the sections claiming Dissenters could not be loyal subjects, though he kept his description of Dissent as a crime.

  In 1785, Priestley published The Importance and Extent of Free Enquiry, in which he compared his theological opponents to a building that gunpowder laid "grain by grain" would one day blow apart. Friends urged him to drop the language. He refused, forever earning the nickname "Gunpowder Joe." That phrase would be used against him in Parliament by both William Pitt and Edmund Burke, who linked Priestley's scientific work to the French Revolution. Burke, in his Reflections on the Revolution in France, wrote that radicals who supported science in Britain "consider men in their experiments no more than they do mice in an air pump."

  Thomas Jefferson, by contrast, wrote of Priestley's An History of the Corruptions of Christianity and An History of Early Opinions concerning Jesus Christ that he had read them "over and over again" and that they were "the basis of my own faith." Jefferson and Priestley exchanged letters on the structure of a university, advice Jefferson used when founding the University of Virginia. Priestley dedicated his General History of the Christian Church to President Jefferson.

• 7. The Priestley Riots and Exile

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  On Bastille Day 1791, Priestley and several Dissenters had arranged a celebratory dinner in Birmingham. Frightened by warnings of violence, Priestley stayed away. The dinner proceeded without him. Rioters gathered outside the hotel, attacked the attendees as they left, then moved to the New Meeting and Old Meeting churches and burned both to the ground.

  Priestley and his wife fled their home. His son William and others stayed behind to protect the property, but the mob overcame them and set fire to Priestley's house, called Fairhill, at Sparkbrook, destroying his laboratory and all the family's belongings. Over three days, the rioters burned twenty-six other Dissenters' homes and three more churches. The careful execution of the attacks and the farcical trials of only a handful of participants convinced contemporaries and later historians alike that the Birmingham magistrates had planned and condoned the violence. When George III sent troops to restore order, he remarked that he could not help but feel satisfied that Priestley was the one suffering for the doctrines he had spread.

  From hiding, Priestley travelled to London and eventually to Lower Clapton in Hackney, where he lectured at New College. In the French National Convention election of the 5th of September 1792, he was elected a representative by at least two departments, Orne and Rhone-et-Loire. He declined, citing his lack of French. A decree of the 26th of August 1792 had already granted him French citizenship as one who had "served the cause of liberty" by his writings. He accepted that honour.

  His sons Harry and Joseph left for America in August 1793. Priestley and Mary boarded the Sansom at Gravesend on the 7th of April 1794. Five weeks after they left, Pitt's administration began arresting radicals for seditious libel in the famous 1794 Treason Trials.

• 8. Final Years and Lasting Reach

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  The Priestleys arrived in New York City on the 4th of June 1794. Factions competed for Priestley's endorsement; he declined all of them. In Philadelphia, before settling in Northumberland County, Pennsylvania, he preached a series of sermons that led to the founding of the First Unitarian Church of Philadelphia. He turned down an offer to teach chemistry at the University of Pennsylvania.

  His son Henry died on the 11th of December 1795, possibly of malaria contracted after landing in New York. Mary Priestley died on the 17th of September 1796. By 1801, Priestley was too ill to write or experiment. He died on the morning of the 6th of February 1804, aged seventy, and was buried at Riverview Cemetery in Northumberland, Pennsylvania. His epitaph, which he chose himself, reads: "Return unto thy rest, O my soul, for the Lord hath dealt bountifully with thee."

  His reach extended well beyond his own life. Immanuel Kant praised him in the Critique of Pure Reason (1781), writing that Priestley "knew how to combine his paradoxical teaching with the interests of religion." Erasmus Darwin, Samuel Taylor Coleridge, William Wordsworth, John Stuart Mill, Alexander Bain, and Herbert Spencer all became associationists in part through Priestley's redaction of David Hartley's Observations on Man.

  The American Chemical Society placed a National Historic Chemical Landmark at the Priestley House in Northumberland on the 1st of August 1994, recognising his discovery of oxygen. The same society marked Bowood House in Wiltshire on the 7th of August 2000. The ACS Priestley Medal, its highest honour, bears his name. Since 1952, Dickinson College in Pennsylvania has presented the Priestley Award to distinguished scientists whose work has contributed to human welfare. An asteroid discovered in 1986 by Duncan Waldron carries the designation 5577 Priestley.