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  Joseph Priestley (1733–1804), by or after Ellen Sharples [original, c.1797] Joseph Priestley (1733–1804), by or after Ellen Sharples [original, c.1797]
Priestley, Joseph (1733–1804), theologian and natural philosopher, was born on 13 March 1733 at Birstall Fieldhead, West Riding of Yorkshire, about 6 miles south-west of Leeds. He was the first of six children of Jonas Priestley (1700–1779), cloth dresser, and his first wife, Mary (d. 1739), daughter of Joseph Swift, farmer and maltster of Shafton near Wakefield. Priestley was a major figure of the British Enlightenment and a notable polymath, and his publications number, in first editions, more than 150 books, pamphlets, and papers in journals. An early nineteenth-century edition of his collected works, minus the science, filled twenty-six octavo volumes and the science would have added at least five more. Remembered today primarily for his isolation and identification of seven gases, including oxygen, in his own day he was known also as a vigorous advocate of unitarianism and of liberal reform of government, education, and theology.

Early life and education, 1733–1755

Priestley's independence of thought and authority was a partial consequence of virtual estrangement from his family. His ‘mother having children so fast’, as he says in his memoirs, Joseph was taken from home to live with his maternal grandfather and there he was to stay, ‘with little interruption till my mother's death’. Even then he was not to live long at the family home, for his father remarried in 1741 and Joseph was sent to the father's older sister and her husband, Sarah and John Keighley, at Old Hall, Heckmondwike, about 3 miles from Fieldhead. The Keighleys were childless, and possessors of considerable property. When John Keighley died in 1745 young Joseph became Sarah's presumptive heir. Though Old Hall and the Independent chapel of Heckmondwike provided a centre for Priestley family social life, Joseph was already on a path diverging from that of his cloth-working family.

Sarah Keighley, impressed with the intelligence of her ward, determined that he should be educated to become a dissenting minister. He learned to read and write probably at a local dame-school, but was then sent to Batley grammar school, where he learned Latin and some Greek, and began his facility in shorthand—Peter Annet's, for whom he wrote some commendatory verses published in an edition of Annet's Expeditious Penmanship (c.1750). From 1746 to 1749 he went to a small school kept by John Kirkby, minister at Heckmondwike Upper Chapel, where he began his study of Hebrew and (probably from a polyglot Bible) the rudiments of Chaldee, Syriac, and Arabic. When, at sixteen, it was thought he might have to go to Lisbon for his health, he taught himself French and High Dutch (German) for service in a counting house. Health recovered, he resumed his plan to become a minister and continued his studies independently with the occasional aid of George Haggerstone, a former student of Colin Maclaurin and Calvinist minister of nearby Hopton.

Some thirty-five years later, when he commenced writing his memoirs, Priestley cited only three books, Isaac Watts's Logic, John Locke's Essay Concerning Human Understanding, and W. James 'sGravesande's Mathematical Elements of Natural Philosophy, as those he read during this period of self-education. His career suggests that they were primarily influential for their treatment of language, of the nature of history, and of Sir Isaac Newton's ‘mechanical philosophy’. Together with his earlier studies, his learning from these works was sufficient to excuse him from the first and most of the second year of the curriculum of his dissenting academy.

As an Independent it was not possible for Joseph to go to Oxford or Cambridge, while the alternatives of Scotland or the continent were excluded by expense. As the eighteenth-century English universities were in the doldrums, certain of the academies established by English dissenters for the education of their ministers and sons could be eminently worthy competitors. That initially selected for Priestley, Zephaniah Marryat's in Stepney, was not one of these, but Joseph, with the support of John Kirkby, refused to go there. And, in any event, he could not have done so. The extended Priestley family in Birstall parish, father, stepmother, aunts, uncles, sisters, brothers, cousins, were all fervent dissenting Calvinists. Joseph's memoirs report the importance of religion in family activities. His mother, ‘the little time I was at home’, taught him the shorter Westminster catechism; he could repeat all its 107 questions and answers ‘without missing a word’ by the time he was four. There were family prayers, morning and evening, at Fieldhead and Heckmondwike. Priestley led those at Old Hall when he became seventeen. He attended weekly prayer meetings, attended chapel twice each Sunday, committing the sermons to memory and writing them down at home. But his serious illness, at sixteen, had brought on a religious crisis. Thinking he might die, he lived months in a state of terror, for he could not persuade himself that he had experienced the ‘new birth’, that religious experience produced by the immediate agency of the spirit of God he had been taught was necessary for his salvation. Fortunately Sarah Keighley entertained the candidates to succeed the superannuated Kirkby as guests at Old Hall and some of these were Baxterians, or even Arminians, and did not believe in the necessity of a new birth. They eased Priestley's mind and even persuaded him that the sin of Adam had not condemned all mankind forever to the wrath of God. A consequence of this liberation, however, was his rejection by the elders when he applied for membership of Heckmondwike Upper Chapel. And without the recommendation of his church he could not attend Marryat's academy, even had he wanted to. His family was forced to choose another.

Priestley's stepmother had been housekeeper for Philip Doddridge, and she and Kirkby recommended his academy at Northampton. Doddridge died in 1751, but his academy was moved to Daventry under the auspices of Caleb Ashworth, a Priestley family connection, and Joseph was sent there, in September 1752, one of the earliest to enrol in the new academy. Daventry Academy continued the liberal practices that had earned Northampton its reputation as one of the finest of the dissenting academies. Priestley was happy there in its spirit of intellectual freedom and though he was later (somewhat unfairly) critical of its curriculum, he was solidly grounded in the classical languages, ancient history, and biblical studies. There he was also schooled in the classics of English literature and in rhetoric and sermon making, though he never quite lost his Yorkshire accent nor his tendency to stammer. He also studied mathematics, anatomy, medical chemistry in the work of Herman Boerhaave, and Newtonian natural philosophy, including the dynamic particle matter theory of John Rowning and the physico-theologians.

Priestley was introduced to metaphysics in a set of lectures by Doddridge, later published as A Course of Lectures on the Principal Subjects in Pneumatology, Ethics, and Divinity (1763). Doddridge's Lectures contained references to many of the early eighteenth-century religious and philosophical controversalists, including the Cambridge Platonists and Samuel Clarke, Anthony Collins, and John Toland. Most important, it referred Priestley to the Observations on Man (1740) by David Hartley, which was to be of enormous influence throughout Joseph's life. Doddridge's teaching practices, begun at Northampton and continued at Daventry and other major dissenting academies, involved the study and comparison of opposing views before reaching a final conclusion. This introduced Priestley to the dialectic process of obtaining truth which made him one of the most contentious theologians of eighteenth-century England, for he came to believe that truth was always ultimately to emerge from the conflict of contending ideas.

Theological debate at Daventry also persuaded Joseph to become an Arian. This partial denial of the doctrine of the Trinity completed the break with his family, for while Joseph was adopting the liberal radical adjustment of eighteenth-century dissent, his family had adopted the conservative evangelical. During the process of finding a new minister for Heckmondwike Chapel they had become evangelical Calvinist Methodists. , Joseph's brother, became a minister in the Countess of Huntingdon's Connexion and it was he who engineered Priestley's disownment, revealing to Sarah Keighley the liberal direction of Joseph's theology. She eventually transferred her financial support to the building of a new chapel at Heckmondwike. From this time, though there were occasional references to family (including, oddly enough, Timothy), Priestley essentially lived without association with the Fieldhead Priestleys or their Leeds and London relations.

Needham Market and Nantwich, 1755–1761

Upon graduation from Daventry Academy in 1755 Priestley accepted the call to assist the ageing minister of the dissenting chapel of Needham Market, Suffolk. Although he had preached at Needham and been interviewed by the congregation, his appointment there was a mistake. The senior minister, the Revd John Meadows, resented his coming, neither his stammer nor his Yorkshire accent was welcome, and no one seemed aware, initially, that he was an Arian. The congregation was poor and Priestley could not qualify for assistance from the Independent fund established to promote the denomination's cause, while the allowance his aunt had promised him should he become a minister was not now forthcoming. Without the aid of Andrew Kippis and George Benson, London ministers with access to various charitable funds, he might have suffered severely and, as it was, the stress increased his stammer, his congregation dwindled, and no one enrolled in the school that he proposed to open.

Rejected by the local dissenting community and in desperate material circumstances, Joseph maintained his spirits by referring to David Hartley's determinism—a wise providence disposed all things for the best—and by concentrating on theological studies. Besides writing a sermon a week, he produced a treatise, The Scriptural Doctrine of Remission, which challenged the orthodox view of atonement by an analysis of relevant texts in the Old and New testaments, to be understood in the cultural and historical context in which they were written. This treatise, published in 1761 with the encouragement of Samuel Clark, his former tutor at Daventry and by Caleb Fleming and Nathaniel Lardner, London leaders of liberal dissenting thought, was Priestley's first use of a method of biblical analysis which was to be taken up in the nineteenth century as ‘the higher criticism’.

It was clear to Priestley's friends that his position at Needham Market was untenable. Benson, Kippis, and Samuel Clark recommended Priestley for a position as tutor of languages and belles-lettres at the newly opening (1757–8) dissenting academy at Warrington, Lancashire, but the trustees were apprehensive about his youth and the report of a ‘hesitation’ in his manner of speaking. They chose, instead, John Aikin, former pupil and assistant of Doddridge and tutor at Kibworth Academy. Thomas Haynes, a distant relation of Priestley's mother, then arranged an appointment for him as minister to the dissenting chapel at Nantwich, Cheshire, where he moved in September 1758.

Priestley's congregation at Nantwich was no larger than that at Needham, but was less obsessed with Priestley's heterodoxies; members were from the same midlands dialect region as his West Riding accent, and sufficiently sympathetic to his stammer as to allow him to learn its control. They also encouraged him to open a school in a building opposite the chapel yard. The school was very successful and lasted, with various vicissitudes, through at least four succeeding ministers and until 1846. Priestley taught both boys and girls (in a separate room) for three years. He taught Latin and some Greek, English grammar, geography, natural and civil history, some mathematics, and natural philosophy, for which he purchased apparatus—an air-pump and electrical machine, among others—that his older pupils operated.

Warrington, 1761–1767

The success of his school at Nantwich prompted the trustees of Warrington Academy to offer Priestley the tutorship in languages and belles-lettres vacated when Aikin was transferred to that in divinity. He accepted the offer, moved to Warrington in September 1761, and immediately fitted happily into the academic community. He made friends with other academy faculty, soon became deputy to John Seddon, resident agent of the academy's committee of managers, was a member of the governors of Warrington's subscription library, and, in May 1762, moved into a new house provided by the trustees. Later in May he was ordained minister at the Warrington Provincial Meeting of the ministers of the county of Lancaster and on 23 June he married Mary Wilkinson (1743–1796), daughter of ironmaster , sister of and of , who had been one of Priestley's students at Nantwich and who followed him to Warrington. Their first child, a daughter, Sarah, was born in April 1763.

At the academy Priestley gave his immediate attention to the languages and belles-lettres for which he had been employed. He taught the classical languages and antiquities, French, and English grammar and composition for which he used the text he had prepared for his Nantwich students. Printed and published in Warrington in 1761, The Rudiments of English Grammar and a companion work, A Course of Lectures on the Theory of Language and Universal Grammar, printed in 1762, had a long and influential history. The Rudiments went through nine English editions and the lectures, though not published, were distributed for use in other dissenting academies. Together these books have earned Priestley the reputation as a major grammarian of his time. His insistence that usage was the only viable standard for correct English and his detailed descriptions of the structure and vocabulary of his day are noted in most modern histories of the English language. His Course of Lectures on Oratory and Criticism (1777) has also won attention from modern students of rhetorical theory. Not himself a gifted speaker, he avoided the subject of elocution, concentrating instead on the other offices of rhetorical theory. There his use of Hartleyan associationism led him to a psychological rationale for topical analysis and for aesthetic taste. Oratory and Criticism was less generally influential than the Rudiments, as the delay in its publication let George Campbell's Philosophy of Rhetoric take precedence in basing rhetoric on human nature, but it is still regarded as one of the classics of modern rhetoric.

Priestley's greatest contribution in making Warrington the most notable of dissenting academies was, however, in his restructuring of its curriculum. In his Essay on a Course of Liberal Education (1765) he argued that the standard course of studies had been designed for pupils entering the learned professions. Most of the students at Warrington and other dissenting academies were intended, instead, for civil, active, and commercial life. A different plan should be adopted and that plan, outlined in the Essay and later developed in his Miscellaneous Observations Relating to Education (1778), showed Priestley as an innovative educational philosopher. Probably the most important of his innovations was the minimizing of language study, except for English, and an emphasis on that of natural history, natural philosophy, and modern history. He had a broad conception of history as involving the social, cultural, and economic aspects of a society as well as its government and laws. A syllabus of his lectures on history was printed in 1765, but the Lectures on History and General Policy were not to be published until 1788.

To supplement his history teaching Priestley prepared and had published two aids to study: a Chart of Biography (1765) and a New Chart of History (1769) with accompanying Descriptions. These graphic time line representations of the span of life of major historical figures or of empires were popular for the rest of the century in England and the United States, and the Descriptions, at least, went through several editions. The time line form of biography was adopted, with acknowledgement to Priestley as late as 1853, by J. C. Pogendorff and that of history by Francis Baily in 1813. More important to Priestley the forthcoming publication of the Chart of Biography was instrumental in his being awarded the LLD degree of Edinburgh University on 4 December 1764 and the Chart is the only publication explicitly cited in his certificate for fellowship in the Royal Society of London.

Although Priestley's interests in science had been growing since his days at Daventry, he had little opportunity of exploring them before going to Warrington and there, because John Holt was tutor in mathematics and natural philosophy, he was, at first, confined to lecturing in anatomy and aiding in the organization of some lectures in chemistry by Matthew Turner. Examples drawn from the sciences in his Oratory and Criticism and in the Description of the Chart of Biography show that he had not lost interest and when, in 1765, he could finally find some time, he commenced writing a didactic history of electricity. Associationist theory maintained that history and geometry were the best approaches to teaching and he could prevail on Seddon to introduce him to John Canton and, through Canton, to Benjamin Franklin, then the foremost authority on electricity in Britain. After going to London he obtained the assistance of Canton, Franklin, William Watson, and Richard Price for his enterprise. They also became his friends and supported his bid to become a fellow of the Royal Society, even before his history was published. After 12 June 1766 Priestley could, and usually would, style himself J. Priestley LLD FRS.

When published, in 1767, The History and Present State of Electricity, with Original Experiments was to be one of Priestley's most successful non-theological publications. The historical part was based, whenever possible, on primary sources and the ‘present state’ on papers in scientific journals and on interviews with his new London friends. The friends also insisted that he perform the experiments that he wrote about. What he had intended as a Baconian histoire became also a manual of competently described experiments and an example of independent work and analysis on his subject. The work went through five English editions and was translated into French and German. A primary source for eighteenth-century understanding of electricity it is credited for the first statement of the inverse square law of electrical force based on reasonable deduction from experiment.

Leeds, 1767–1773

Hardly had the History of Electricity been published when Priestley received an invitation to be minister to the dissenting congregation of Mill Hill Chapel in Leeds. He accepted the call and moved in September 1767. His memoirs cite Mary Priestley's bad health to explain the move and one can add that the financing of Warrington was always uncertain and there was little prospect for an increase in salary to match a possibly increasing family. Additionally, Priestley was always to regard the role of dissenting minister as the most important of any in the world and he was here invited to return to it for a major congregation and one within the cognizance of his family. He was, that is, returning a success to the ‘home’ that had rejected him.

The Mill Hill congregation was a liberal one and supported Priestley's move from Arianism to complete anti-Trinitarianism. This probably occurred in 1769 after he re-read Nathaniel Lardner's Letter … [on] the Logos (1759). The Priestleys were happy in Leeds, though there is no record of visits to or from Fieldhead. Joseph junior was born there in July 1768 and William in May 1771. Priestley took a minor part in community activities. He helped organize the Leeds proprietary circulating library and preached annual charity sermons for the charity school and general infirmary. And it was there that he began his long career in religious and polemical publication.

Anxious to succeed as a minister Priestley exploited his major talent, that of teacher, by organizing religious classes within his congregation. He wrote catechisms for two younger groups and a text, Institutes of Natural and Revealed Religion (1772, 1773, 1774), to teach the principles of rational dissent. He had begun the Institutes while a student at Daventry, and its publication was not completed until after he had left Leeds, but it soon became a standard exposition of Unitarian beliefs. He also attacked the sacramental nature of the Lord's supper, recommended family religious exercises and a renewal of some kind of church discipline, and supported the practice of infant baptism. His pamphlets An Appeal to the Serious and Candid Professors of Christianity (1770) and Familiar Illustration of Certain Passages of Scripture (1772) went through multiple editions—30,000 copies of the Appeal being circulated by 1787. And he established the first English scholarly journal for speculative theology, the Theological Repository, published in three annual volumes (1769–71) and then suspended for lack of support from any contributors but Arians or Unitarians. Priestley himself contributed about one third (fifteen articles) of the early Repository's contents.

Each of his religious publications elicited attacks and, to most of these attacks, Priestley published at least one answer. This was partly because he sincerely believed that controversy was the best avenue towards truth, but also, it is clear from his polemical works, because he enjoyed debate. He developed a style of patient condescension and irony which, from this provincial schoolmaster and dissenting minister, infuriated his opponents, usually university graduates. Although not conducive to convincing his opponents, his polemics were to make of Priestley the most prominent English spokesman for rational theology in the later eighteenth century.

They were also to make Priestley a major spokesman for liberal political reform. In his Liberal Education he had objected, partially on political grounds, to a scheme for national education. His friends encouraged him to develop these ideas further in his Essay on the First Principles of Government (1768), which separated the concepts of civil and political liberty and used a principle of utility which Jeremy Bentham was to claim, in his ‘Short history of utilitarianism’ (1829), was the source of his own normative greater happiness principle. Priestley's Remarks on some Paragraphs in … Blackstone's Commentaries (1769) objected to William Blackstone's description of dissenters as tolerated criminals and succeeded in making Blackstone retract some of his statements and moderate his language in others. In the same year Priestley's anonymous Present State of Liberty in Great Britain and her Colonies reflects his, and his congregation's, concern over the economic and political consequences of government action toward Britain's American colonies. This plea for liberal reform in politics led, in turn, to pamphlets on liberal reform in church establishment.

None of his Leeds activities precluded Priestley's scientific investigations. Indeed, he regarded both the politics and the science as aspects of his theological work. He sent five papers of electrical experiments to the Royal Society between 1768 and 1770 in which he explored aspects of electrical spark discharge, including an early reference to oscillatory discharge of Leyden jars, and a study of comparative conductivities / impedances. He also prepared Familiar Introductions, teaching manuals for electricity (1768) and perspective (1770), and commenced preparations for a series of volumes on the history of experimental philosophy to follow his History of Electricity.

For the first of these volumes Priestley chose the history of optics, on which there was abundant information. He had to publish by subscription and the History and Present State of Discoveries Relating to Vision, Light and Colours (1772) was a disappointment. The subject required mathematics, which he had determined not to use, and the excess of information called for a nicety of judgement that Priestley was unable to supply. Though it was favourably reviewed many of the subscribers defaulted payment and the only advantage Priestley gained was his reintroduction to a dynamic particle theory of matter in the detailed form proposed by the Abbé Roger Joseph Boscovich in his Philosophiae naturalis theoria (1763).

As he had not received an adequate financial return for his labours on the Optics, Priestley declared that he would not continue his histories. He had, however, already become intrigued by ‘taking up some of Dr. [Stephen] Hales's inquiries concerning air’, as he wrote to his friend Theophilus Lindsey in 1770, and doubtless would not have continued writing about other people's discoveries anyway. He had been doing some chemical experiments as early as his work on electricity. When living next to a brewery the ready supply of by-produced carbon dioxide led him to seek applications for what was then termed fixed air. His first explicitly chemical publication Directions for Impregnating Water with Fixed Air (1772) developed out of a contemporary mistaken view that scurvy was a putrefactive disease associated with the loss of carbon dioxide from the body tissues. The publication elicited much favourable attention and ultimately led to the establishment of the carbonated beverage industry.

Priestley's study of airs (gases) took a more significant form in his long paper, ‘Observations on different kinds of air’, published in the Philosophical Transactions of the Royal Society for 1772. Seldom has a first paper been so important: it announced the isolation and identification of nitric oxide and anhydrous hydrochloride acid gases, introduced the notions of eudiometry and of photosynthesis, and described simple apparatus and manipulative techniques that enabled others to extend his work. The paper richly deserved the Copley medal conferred by the Royal Society for 1773.

Calne, 1773–1780

By the time he received the medal Priestley had moved from Leeds and Mill Hill Chapel to Calne, Wiltshire, and the service of William Petty, second earl of Shelburne. The combined failures of the Theological Repository and the History of Light had brought financial problems and Priestley's friends also agreed that Leeds was too small a niche for a man of his abilities. There had been one abortive effort to extract him when Joseph Banks, planning to go on James Cook's second voyage to the south seas as supernumary botanist, invited Priestley to accompany him as an astronomer. The invitation, in December 1771, had to be withdrawn when Banks realized that he had exceeded his authority in offering the appointment and that Priestley lacked the astronomical expertise demanded by the board of longitude and the Royal Society. Franklin failed to locate an academic post for him in the colonies and, finally, Richard Price came to the rescue by recommending him to Lord Shelburne for a post of companion at a salary of £250 and a house. The Priestleys moved to Calne, near Shelburne's estate of Bowood, in June 1773.

Shelburne was a major figure in the Chathamite faction in opposition to the North ministry and Priestley was a vigorous representative of the most vocal part of dissenting interests. Priestley and Shelburne were too unlike to become the kind of companions that Shelburne had wanted, but Priestley could provide political information and intellectual consequence. He performed experiments for Shelburne's guests, supervised the education of his children, and acted as librarian, buying books and cataloguing the library and manuscript collections. The Calne years were good ones for Priestley. During them he became an important political voice among British dissenters, as well as developing a metaphysical position and continuing his theological and pneumatic studies. His third son, named Henry at Shelburne's request, was born there in May 1777.

Priestley's first political chore for Shelburne was to summarize dissenting opinion respecting the attempted repeal, in 1773, of the Test Act. Failure of that attempt led to a pamphlet advising dissenters on conducting the next appeal, including suggestions on reform of the established church. It also led to his Address to Protestant Dissenters on the Approaching Election (1774) attacking the parliamentary majority for its failure to repeal and for its activities relating to the colonies. The Address was the most extreme political tract Priestley had written and attracted the most national attention of any appeal favouring the Americans. Continuation of the North ministry dampened overt political activity though Priestley continued to act as intermediary between Shelburne and dissenters and, as an impartial agent, between the allies of the marquess of Rockingham and the Chathamites. His only visit to the continent was during August to October 1774, in the company of Shelburne.

Not having a congregation in Calne, Priestley's religious activities were confined to occasional preaching and publications such as his homily advocating premarital celibacy. He supported Theophilus Lindsey in establishing Essex Street Chapel, the first avowedly Unitarian place of worship in England and he again directed his attention to formal theology. He attempted a chronological arrangement of passages in the four gospels in a Harmony of the Gospels, in Greek (1777), and in English (1780). Though a somewhat conventional approach to biblical study prior to synoptic analysis, his Harmony inevitably led to a pamphlet argument. He also published the first of a continuing series of letters answering atheistic arguments, this one addressed to Holbach and Hume. His most singular activity of this period was the writing of five metaphysical works, starting with an acerbic attack on several leading Scottish philosophers, An Examination of Dr. Reid's Inquiry … Dr. Beattie's Essay … and Dr. Oswald's Appeal (1774), presenting an alternative to their doctrine of common sense. He followed this with an edition of that part of David Hartley's Observations on Man which provided an associationist alternative to the common-sense philosophers. His Hartley's Theory of the Human Mind (1775) provided an influential source for Hartley's ideas into the next century.

One of the introductory essays to the Hartley announced Priestley's adoption of monism, which he was then obliged to defend in his Disquisitions on Matter and Spirit (1777), followed by his Doctrine of Philosophical Necessity (1777), which supported a type of mechanistic determinism. Together these books started a flood of criticism which Priestley attempted to answer in a Free Discussion of the Doctrines of Materialism and Philosophical Necessity (1778) with his good friend Richard Price. Price was never to understand, nor did the majority of Priestley's contemporaries, that Priestley saw matter as the manifestation of spiritual force and determinism as an active acceptance of causality in the will of God.

During the period of his metaphysical writing Priestley was also continuing his pneumatic investigations. Except for occasional Philosophical Transactions papers, such as that of 1776 which inspired Lavoisier's oxidation theory of respiration, these appeared as books. The papers, and the volumes of experiments and observations—Experiments and Observations on Different Kinds of Air (1774, 1775, 1777) and Experiments and Observations Relating to Various Branches of Natural Philosophy (1779)—were eagerly awaited for their new discoveries and new techniques. In them, he announced his discovery of ammonia gas, nitrous oxide, nitrogen dioxide, sulphur dioxide, and, most important, of oxygen. The latter, for which he is most famous, was first mentioned in Transactions letters (1775) and was described in detail in the book of that year. He also wrote a vigorous defence again a charge of scientific plagiarism and expanded his pneumatic studies beyond chemistry into investigations of heat expansion, indices of refraction, and sound transmission of gases and continued his study of photosynthesis.

Birmingham, 1780–1791

Lack of real companionship between Priestley and Shelburne was amplified by the latter's becoming head of the Chathamite whigs on Lord Chatham's death (1778) and his remarriage in 1779. The Priestleys had become political and social impediments. By mid-1780 the association was broken and Priestley retired to Birmingham, retaining an annual pension of £150. By December he accepted an invitation to be senior minister of New Meeting, one of the largest and most affluent dissenting congregations in England, at a salary of £100 and he was, once again, happy in his real vocation. He retained his scientific avocation, particularly in becoming a member of the , comprising entrepreneurs and scientists such as Matthew Boulton, Erasmus Darwin, James Watt, Josiah Wedgwood, and William Withering. Most of his Birmingham science was in the area of applied science, in service of the interests of that group or of his brother-in-law, the ironmaster John Wilkinson. Priestley advised Wedgwood on the airs entrapped in ceramic clays, Boulton on the cost and elasticity of the new gases, Watt and Wilkinson on steam interaction with iron, and Withering on the inexpensive generation of hydrogen for balloon flight. Priestley continued sending occasional papers to the Royal Society for publication, including a confusing set ultimately revealing the diffusion of gases through unglazed ceramic walls. His volumes of Experiments and Observations Relating to … Natural Philosophy were continued (1781, 1786) and in 1790 he published an ‘abridged and methodized’ version of the six-volume Experiments and Observations. The originality in the earlier volumes had, however, chiefly disappeared and the major theme of his published science during the remainder of his life was his conflict with Antoine Lavoisier, who had used his discovery of oxygen and the work of Watt and Cavendish on the composition of water (started by hints from Priestley) to attack the doctrine of phlogiston. Priestley never accepted Lavoisier's interpretation of oxygen, nor the composite nature of water and his criticisms of Lavoisier's experiments, though frequently correct, could not succeed in face of the systematization and pedagogic usefulness of the Lavoisian taxonomic revolution of chemistry.

Most of Priestley's time was devoted to the role of minister, which he happily resumed. During the Birmingham years he was to publish thirty-eight pamphlets or books, some of the latter in several volumes, on religious and educational issues, including sermons, prayers, exhortations to Jews, an edition of hymns, annotations for an edition of the Bible, and the resumed publication of the Theological Repository (1784, 1786, 1788). He preached regularly and, as in Leeds, conducted religious classes for children and young adults in the New Meeting congregation. Priestley's Sunday class had a total membership of nearly 150, of whom 80 were aged between seventeen and thirty. He also joined members of Old and New Meeting in establishing Sunday schools at which nominees of the congregations could learn reading, writing, sums, and basic job skills and that led to the Birmingham Sunday Society—open to any former pupil of a basic Sunday school in town—at which were taught natural and revealed religion and a range of philosophical subjects.

In 1788, Priestley's Lectures on History and General Policy, first delivered at Warrington Academy, were finally published. They did not have the influence they warranted, though there were to be seven English editions and translations into German and French, but they were adopted for use in dissenting academies throughout England, in universities in the United States, and even, it is said, were used by John Symonds at Cambridge and Thomas Arnold at Oxford. More historiographic than narrative, and in the exemplary rather than the nineteenth-century historicism mode, still the Lectures supported a doctrine of progress and recommended a wide variety of sources for research into a broadly defined social, economic, and cultural as well as political and diplomatic history.

Priestley's major historical work of the period was also theological, in that he wrote some five historio-theological works dedicated to the single purpose of establishing an uncompromising monotheism. In Priestley's opinion both Arianism and Trinitarianism were compromises between the monotheism of Judaism and the early Christian church and the polytheism of Hellenistic gnosticism and neo-Platonism. To prove this he wrote An History of the Corruptions of Christianity (1782) in two volumes, and, in response to the arguments that caused, An History of Early Opinions Concerning Jesus Christ (1786), in four. Positions adopted in these works—insistence that the early Christian church had been unitarian, denial of the virgin birth of Christ, and supporting Nazareth as his birthplace—led to increasingly intemperate argument, especially with Samuel, soon to be Bishop, Horsley, who attacked Priestley's scholarship without addressing the substance of his arguments. Soon there were annual volumes in defence of Unitarianism, and, in 1790, a two-volume General History of the Christian Church to the Fall of Empires. Altogether, counting the pamphlet war, Priestley wrote nearly 4800 pages in this cause and many of his arguments have been sustained by modern, liberal scholarship.

Anger of many clergymen at their inability to silence Priestley's theological arguments was increased by his support of attempts to repeal the Corporation and Test Acts, represented, for example, in his Letter to the Rt. Honourable William Pitt (1787) and his sermon of 1789 (for he regarded repeal to be a religious issue), The Conduct to be Observed … to Procure the Repeal of the Corporation and Test Acts. Priestley's enthusiastic welcoming of the French Revolution, evidenced in his Letters to the Rt. Hon. Edmund Burke (1791), convinced many people that he was a revolutionary, bent on destruction of church and crown. Untrue though these suspicions were they encouraged members of the Birmingham establishment to acquiesce, at least, in those acts of mob violence variously known as the Birmingham, church and king, or Priestley riots of 1791. The immediate excuse for the riots was a dinner in celebration of Bastille day, held by the Constitutional Society of Birmingham, a dinner which Priestley did not attend though he had assisted in the organization of the society. The riots raged from the evening of the 14th of July to that of the 16th, and were put down only at the arrival of dragoons sent from Nottingham. Damage was extensive: Old and New Meeting houses and seven residences were destroyed, other houses were wrecked. Priestley's house, his library, laboratory, and papers were ruined and his life was saved only because he had fled. English authorities generally approved of the riots, but they were denounced by many persons and organizations in England, Europe, and the United States and remain a blot on the history of British toleration.

Hackney, 1791–1794

Priestley found temporary refuge with friends and then, in November, settled in Clapton, near Hackney, and accepted the invitation to succeed Richard Price, whose funeral sermon he had preached six months earlier, as morning preacher at Gravel Pit meeting. He was discouraged from returning to Birmingham with a sermon—‘Forgive them Father, they know not what they do’—guaranteed to incite the establishment to blind fury. Only seventeen of the rioters were ever tried and, of these, only notorious criminals were convicted. Compensation paid the victims by assessment on Hemlingford hundred was woefully inadequate, but John Wilkinson made Priestley an annual allowance of £200, and settled on him an (unproductive) £10,000 in French funds. He was elected a citizen of France, which he accepted, and a representative to the National Convention, which he declined.

Priestley's polemical and theological work continued, as in his An Appeal to the Public on … the Riots in Birmingham (1791), which went through four printings in a year. He continued his series pamphlet war on atheists, this time attacking Gibbon's Decline and Fall; Gibbon declined to respond publicly. Priestley lectured on history and on natural philosophy at Hackney New College, publishing his only general statement on the latter in his Heads of Lectures on a Course of Experimental Philosophy (1794). Hackney was not, however, a satisfactory solution to his problems. He missed his friends of the Lunar Society, associates of the Royal Society avoided him, and he ceased attending meetings, publishing his continued attack on Lavoisian chemistry, Experiments on the Generation of Air from Water (1793) as a separate pamphlet. His sons were unable to find employment and attempts of the younger Pitt's administration to silence all criticism were coming closer and closer to him. Finally, in 1794, he resolved to emigrate to the United States.

Pennsylvania, 1794–1804

After obtaining official notice that he was not fleeing arrest Priestley sailed with his wife, on 8 April 1794, for the United States. They arrived at New York city on the evening of 4 June, to be met by Joseph junior and his wife and, the following day, by official greetings from Governor Clinton, and deputations from merchants and various patriotic societies all expressing delight at their arrival. A fortnight later the Priestleys went to Philadelphia where, again, they were warmly welcomed. In mid-July they began their five-day journey, 130 miles, to Northumberland, Pennsylvania, where they were to stay while a community of emigrating English liberal dissenters and reformers was to be established on the nearby 700,000 acres of land optioned to Priestley's sons and Thomas Cooper. The projected community was never realized as the expected flood of refugees from the younger Pitt's liberal witchhunt failed to materialize after the acquittals in the high treason trials of Thomas Hardy, Horne Tooke, and John Thelwall late in 1794. Nevertheless the Priestleys remained at Northumberland. Experiences of the Birmingham riots had given Mary Priestley a distaste for cities, and the location in central Pennsylvania, at the junction of two branches of the Susquehanna River, was an attractive one. There they were to build their home, though Harry, who died in late 1795, and Mary, who died on 17 September 1796, never saw the completed house. Priestley moved into it, along with the family of Joseph junior, and there he was to stay, with occasional visits to Philadelphia, until his death.

When the Priestleys had left England they were recipients of many public statements of sorrow and support. In New York and Philadelphia, Priestley was welcomed as a friend of liberty and a distinguished philosopher who had been badly treated in England. He visited President Washington several times and was befriended by Thomas Jefferson as ‘one of the few lives precious to mankind’. Not everyone was as welcoming and Priestley was to discover that bias and bigotry were as evident in the United States as in England. William Cobbett, just embarked on his career as reactionary radical journalist, was incensed at the criticism of England implied in the reception given Priestley and, under the name Peter Porcupine, crudely attacked him as a friend of anarchy and godlessness. Many ministers preached against him in their pulpits and he was unable to establish himself as a minister in any church, though he preached occasionally in Philadelphia, where he assisted the formation of a small Unitarian society, and regularly at services held in his home in Northumberland.

It was the summer of 1795 before Priestley could return to his experiments and though he was to build a laboratory and publish more scientific papers (at least forty), in the Transactions of the American Philosophical Society and the New York Medical Repository, as well as two pamphlets affirming his continued belief in phlogiston, his scientific work was essentially an anticlimax. He inspired a number of young chemists in the United States to experiment, had an indirect influence in the identification of carbon monoxide as a new gas, and extended his interests to opposing Erasmus Darwin's belief in spontaneous generation and writing an essay on hearing and another on dreams. In essential isolation he kept up as well as he could with the news in science, experimenting, for example, with the newly discovered voltaic cell. But most of his work was a repetition of experiments he had done before, inadvertently illustrating Priestley's own complaint that he frequently forgot things he had done in the past. His futile opposition to Lavoisian chemistry was a solitary one.

Priestley retained his political interests. In February 1798 he wrote an anonymous article, ‘Maxims of political arithmetic’, published in the Republican newspaper, Aurora, which John Adams, elected president in 1797, regarded as attacks on his policies. Reacting to French interference in American politics, and to suppress criticism, the Adams administration had passed the Aliens and Sedition Acts, which Timothy Pickering, secretary of state, wanted to apply to Priestley. Responding to federalist attacks, Priestley wrote Letters to the Inhabitants of Northumberland (1799) to defend himself. Adams rejected Pickering's suggestion—Priestley's influence was too weak to take that seriously—but Priestley was not to feel completely secure until the election to the presidency of Jefferson, to whom he wrote, in dedicating the second part of his church history (1802), ‘Tho' I am arrived at the usual term of human life, it is now only that I can say I see nothing to fear from the hand of power, the government under which I live being for the first time truly favourable to me.’

Priestley's most effective activities in exile were in education and theology. He had an extensive correspondence with Jefferson on the establishment of the latter's new college for the state of Virginia, including a lengthy ‘Hints concerning public education’, which echoed his Warrington recommendations, but with some specifics such as the number of professors (nine) that would be needed for a fledgeling college and the value of a good library, though students should not be encouraged to read while ‘under tuition’. He delivered two sets of discourses on the evidences of revealed religion, continued his series of attacks on atheistic ideas—this time those of Tom Paine and those of Constantin Volney, and completed his General History of the Christian Church (1802–3). He wrote notes on the scriptures and prepared his Index to the Bible (1804). Of more than twenty theological publications while in America the most noteworthy is perhaps Socrates and Jesus Compared (1803), which was among Jefferson's favourite religious reading. His last works, corrected on his deathbed, were theological, particularly the Doctrines of Heathen Philosophy Compared with those of Revelation.

Priestley died on 6 February 1804 in his Pennsylvania home. He was buried beside his wife and son, Henry, in the Friends' burial-ground in Northumberland. His daughter, Sarah Priestley Finch, predeceased him (1803). His eldest son, Joseph Priestley, returned to England in 1812 and died there (1863). The younger Joseph's first son remained in the United States and continued the Priestley line there, but his eldest daughter married a Birmingham politician, Joseph Parkes. Their daughter Bessie married Louis Belloc, and their children included Hilaire Belloc and Marie Belloc Lowndes. Of Priestley's other children, William Priestley was a disappointment to his father. Though he had married a Miss Peggy Foulke in February 1796, he was unable to settle down. In 1800 he created a scandal by putting tartar emetic in the family flour before departing to become a sugar planter in Louisiana. His daughter Catherine married another sugar planter named Richardson and their son, Henry Hobson Richardson, became a towering figure in the history of American architecture.

When most of the reforms he had advocated were achieved in the nineteenth century, and then superseded, Priestley was forgotten, except as a name occasionally cited in dispersed topical histories. Even in theology, to which he had devoted most of his efforts, he became a remote historical figure. German theologians surpassed him in revisionary scholarship and the sentimental ecumenism of W. E. Channing and James Martineau replaced his militancy in unitarianism. Only in science, usually the least historical of areas, has his memory remained bright—as the discoverer of oxygen, who never quite recognized his own discovery, and as the persistent critic of Lavoisian chemistry who, with the advent of physical chemistry, was shown to be not entirely wrong. His house and laboratory at Northumberland became a museum and the American Chemical Society was planned by men meeting on its porch on 1 August 1874. Memorials and brief biographies of Priestley have been published since his death, but only during the last years of the twentieth century was the full range of his accomplishments recognized.

Robert E. Schofield


R. E. Schofield, The enlightenment of Joseph Priestley: a study of his life and works from 1733 to 1773 (1997) · R. E. Schofield, The enlightened Joseph Priestley (2001) · The theological and miscellaneous works of Joseph Priestley, ed. J. T. Rutt, 25 vols. in 26 (1817–32); repr. (1972), esp. vol. 1 · R. E. Crook, A bibliography of Joseph Priestley, 1733–1804 (1966) · C. C. Sellers, ed., ‘The Priestley family collection, Dickinson College’, Genealogy (1965), 13–19 · minute books, Senatus Academicus, U. Edin. · election certificate, RS · Memoirs of Dr Joseph Priestley, ed. J. Priestley, T. Cooper, and W. Christie, 2 vols. (1806) · D. R. N. Lester, History of Batley grammar school, 1612–1962 [1962]


American Philosophical Society, Philadelphia, corresp. and papers · Beds. & Luton ARS, biographical chart of the world · Library of Birmingham, letters and sermons · Library of Birmingham, papers relating to damages claimed after ‘Priestley riots’ · Dickinson College Library, Carlisle, Pennsylvania, corresp. and papers · DWL, corresp. and papers · Harris Man. Oxf., notebooks and sermons · Leeds Central Library, Leeds Leisure Services, MS address and sermon relating to Birmingham riot · RS, Priestleyana · U. Birm. L., letters · University of Pennsylvania, Philadelphia, Van Pelt Library, corresp. and papers |  American Philosophical Society, Philadelphia, corresp. with Benjamin Franklin · American Philosophical Society, Philadelphia, letters to John Vaughan · Library of Birmingham, letters to Matthew Boulton · Library of Birmingham, letters to James Watt · BL, letters to William Russell, Add. MS 44992 · Bodl. Oxf., Bowood papers · Bodl. Oxf., letters to Richard Price · DWL, letters to Theophilus Lindsey · Hist. Soc. Penn., letters to Benjamin Barton, etc. · N. Yorks. CRO, corresp. with Christopher Wyvill · NRA, corresp. with Sir Joseph Banks · NRA, priv. coll., letters to Lord Lansdowne · RS, corresp. with J. Canton · RS, letters to Josiah Wedgwood · Warrington Library, Cheshire, corresp. with John Wilkinson


oils, c.1760, Unitarian Memorial Church, Cambridge · oils, 1763–5, RS · G. Ceracchi, Wedgwood medallion, 1779, Brooklyn Museum, New York · J. Opie, oils, c.1781, Harris Man. Oxf. · H. Fuseli, oils, c.1783, DWL · J. G. Hancock, medal sculpture, 1783, NPG · J. Millar, oils, 1789, RS · J. Gillray, caricature, etching, pubd 1791, BM · T. Holloway, mezzotint, pubd 1792 (after his earlier work), NPG · J. Sayers, etching, pubd 1792 (after his earlier work), NPG · W. Artaud, oils, exh. RA 1794, DWL · Phipson, medallion, c.1795 (after G. Ceracchi), NPG · R. Peale, oils, c.1800, New York Historical Society; copies, American Philosophical Society, Philadelphia · G. Stuart, oils, c.1803, Smithsonian Institution, Washington, DC, National Portrait Gallery · C. Turner, mezzotint, pubd 1836 (after H. Fuseli), NPG · E. B. Stephens, statue, 1860, New Museum, Oxford · J. F. Wilkinson, statue, 1874, Birmingham · G. Bayes, statue, 20th cent., Russell Square, London · T. Halliday, medallion (after Hollins), NPG · M. Haughton junior, wash over pencil and chalk drawing, BM · Hollins, plaster medallion, DWL · J. Opie, oils, Brompton Hospital, London · J. Sayers, etchings, NPG · by or after E. Sharples, drawing (original, c.1797), NPG [see illus.] · J. Sharples, pastel drawing, NPG; related drawings, NPG · bronze medal, NPG · oils (after G. Stuart), Birmingham Museums and Art Gallery · oils, RS · portraits, repro. in J. McLachlan, Joseph Priestley, man of science, 1733–1804: an iconography of a great Yorkshireman (1983) · statue, Leeds · statue, Warrington · statue, Birstall, West Yorkshire

Wealth at death  

house and lot in Northumberland, Pennsylvania; large library; virtually nothing else: Priestly, Cooper, and Christie, eds., Memoirs