Joseph Priestley was born, a cloth-dresser’s son, at Fieldhead in Birstall parish, Leeds, 13th March 1733. After four years at a Dissenting academy at Daventry, in 1755 he became Presbyterian minister at Needham Market, and wrote “The Scripture Doctrine of Remission,” denying that Christ’s death was a sacrifice, and rejecting the Trinity and Atonement. In 1758 he removed to Nantwich, and in 1761 became a tutor at Warrington Academy. In yearly visits to London he met Franklin, who supplied him with books for his “History of Electricity” (1767). In 1764 he was made LL.D. of Edinburgh, and in 1766 F.R.S. In 1767 he became minister of a chapel at Mill Hill, Leeds, where he took up the study of chemistry. In 1774, as literary companion, he accompanied Lord Shelburne on a continental tour, and published “Letters to a Philosophical Unbeliever.” But at home he was branded as an atheist in spite of his “Disquisition relating to Matter and Spirit” (1777), affirming from revelation our hope of resurrection. He was elected to the French Academy of Sciences in 1772 and to the St. Petersburg Academy in 1780. He became in that year minister of a chapel at Birmingham. His “History of Early Opinions concerning Jesus Christ” (1786) occasioned renewed controversy. His reply to Burke’s “Reflections on the French Revolution” led a Birmingham mob to break into his house and destroy its contents (1791). He now settled at Hackney, and in 1794 removed to America, where he was heartily received; at Northumberland, Pa., he died 6th February 1804, believing himself to hold the doctrines of the primitive Christians, and looking for the second coming of Christ. Priestley is justly called the father of pneumatic chemistry; good authorities (see “Nature,” xlii. 1890) defend the priority of his discovery of oxygen (1774) and of the composition of water (1781), and deny Lavoisier’s claim to be considered an independent discoverer. See Rutt’s edition of Priestley’s “Works” (1831–32), including Autobiographical Memoir; and Martineau’s “Essay.”

Personal

  This morning an express arrived at the Secretary of State’s office from Birmingham, with an account that a great number of persons, to the amount of some hundreds, who were in opposition to the Revolutionists, had assembled on Thursday last before the house where the Society dined, and broke all the windows. They then pulled part of the house down, and proceeded to the different meeting-houses, which they laid level with the ground. After which, they broke into the house of Dr. Priestley, took everything out, burnt his books, drank the wine, and other liquor found in his cellars, and, when the express came away, were demolishing the house to the foundation. The whole town was in an uproar…. A messenger was dispatched to His Majesty at Windsor with the above particulars.

  Seeing, as I passed, a house in ruins, on inquiry I found it was Dr. Priestley’s. I alighted from my horse, and walked over the ruins of that laboratory which I had left home with the expectation of reaping instruction in; of that laboratory, the labours of which have not only illuminated mankind, but enlarged the sphere of science itself; which has carried its master’s fame to the remotest corners of the civilized world; and will now, with equal celerity, convey the infamy of its destruction to the disgrace of the age, and the scandal of the British name.

  When I wrote my last, little did I forsee what soon after happened; but the will of God be done. The company were hardly gone from the inn, before a drunken mob rushed into the house, and broke all the windows. They then set fire to our meeting-house, and it is burned to the ground. After that they gutted, and, some say, burned the old meeting. In the meantime, some friends came to tell me that I and my house were threatened, and another brought a chaise to convey me and my wife away. I had not presence of mind to take even my MSS.; and after we were gone, the mob came and demolished everything, household goods, library, and apparatus. Indeed, they say the house itself is almost demolished, but happily no fire could be got, so that many things, but I know not what, will be saved. We thought that when it was day, the mob would disperse, and therefore we kept in the neighbourhood; but finding they rather increased, and grew more outrageous with liquor, we were advised to go off, and are now on our way to Heath. My wife behaves with wonderful courage. The recollection of my lost MSS. pains me the most, especially my Notes on the New Testament, which I wanted only five days of getting all transcribed. But, I doubt not, all will be for good in the end. I can hardly ever live at Birmingham again.

  Sir, and most illustrious associate, the Academy of Sciences have charged me to express the grief with which they are penetrated at the recital of the persecution of which you have been lately the victim. They all feel how much loss the sciences have experienced by the destruction of those labours which you had prepared for their aggrandizement. It is not you, Sir, who have reason to complain. Your virtue and your genius still remain undiminished, and it is not in the power of human ingratitude to forget what you have done for the happiness of mankind.

  His love to man was great, his usefulness greater. I have been informed by the faculty that his experimental discoveries on air, applied to medical purposes, have preserved the lives of thousands; and, in return, he can scarcely preserve his own. A clergyman attended this outrage, and was charged with examining and even pocketing the manuscripts. I think he paid the Doctor a compliment, by showing a regard for his works. I will farther do him the justice to believe he never meant to keep them, to invade the Doctor’s profession by turning philosopher, or to sell them, though valuable; but only to exchange them with the minister for preferment.

  I have seen Priestley. I love to see his name repeated in your writings. I love and honor him, almost profanely.

  I have lived much among the friends of Priestley, and learned from them many peculiar opinions of that man, who speaks all he thinks. No man has studied Christianity more, or believes it more sincerely.

  Yours is one of the few lives precious to mankind, and for the continuance of which every thinking man is solicitous. Bigots may be an exception.

  On Monday morning, the 6th of February, after having lain perfectly still till four o’clock in the morning, he called to me, but in a fainter tone than usual, to give him some wine and tincture of bark. I asked him how he felt. He answered, he had no pain, but appeared fainting away gradually. About an hour after, he asked me for some chicken-broth, of which he took a tea-cup full. His pulse was quick, weak, and fluttering, his breathing, though easy, short. About eight o’clock he asked me to give him some egg and wine. After this, he lay quite still till ten o’clock when he desired me and Mr. Cooper to bring him the pamphlets we had looked out the evening before. He then dictated as clearly and distinctly as he had ever done in his life, the additions and alterations he wished to have made in each. Mr. Cooper took down the substance of what he said, which, when he had done, I read to him. He said Mr. Cooper had put it in his own language; he wished it to be put in his. I then took a pen and ink to his bed-side. He then repeated over again, nearly word for word, what he had before said; and when I had done, I read it over to him. He said, “That is right; I have now done.” About half an hour after he desired, in a faint voice, that we would move him from the bed on which he lay to a cot, that he might be with his lower limbs horizontal, and his head upright. He died in about ten minutes after we had moved him, but breathed his last so easy, that neither myself nor my wife, who were both sitting close to him, perceived it at the time. He had put his hand to his face, which prevented our observing it.

  Dr. Priestley, after he had abjured the Holy Ghost, and satisfied himself that Jesus Christ was nothing more than a man; that the scriptural writers were no more inspired than himself; and that the soul of man had no existence, retained the same devout passion for preaching, praying, and catechising, which he acquired while he believed in the Trinity and the immateriality of the sentient principle of his nature…. We have already said, that we believe him to have been sincere in the singular profession of faith which he promulgated; and therefore, we are constrained to respect his endeavours to confirm and recommend it. But it is impossible not to regret the presumption and infatuation by which he seems to have been guided; and we are afraid that the theological speculations of a man of great learning, sagacity, industry, and devotion, are at this day an offence to the serious, and a jest to the profane.

  Priestley was a good man, though his life was too busy to leave him leisure for that refinement and ardour of moral sentiment, which have been felt by men of less blameless life. Frankness and disinterestedness in the avowal of his opinion, were his point of honour. In other respects his morality was more useful than brilliant. But the virtue of the sentimental moralist is so over precarious and ostentatious, that he can seldom be entitled to look down with contempt on the steady, though homely, morals of the household.

  Every person of sober mind, whilst commiserating Dr. Priestley as an unfortunate man, and esteeming him as a very ingenious one, could view him in no other light than as the victim of his own folly and misguided passions.

  In nothing did Dr. Priestley’s mental and moral freedom more nobly manifest itself than in his well-proportioned love of truth. With all his diversity of pursuit, he did not think all truth of equal importance, or deem the diffusion of useful knowledge an excuse for withholding the more useful. With all his ardour of mind, he did not look at an object till he saw nothing else, and it became his universe. He made his estimate deliberately; and he was not to be dazzled, or flattered, or laughed out of it. In his laboratory, he thought no better of chemistry than in his pulpit; and in the drawing-rooms of the French Academicians, no worse of Christianity than by the firesides of his own flock. He was never anxious to appear in either less or more than his real character.

  His character is a matter of no doubt, and it is of a high order. That he was a most able, most industrious, most successful student of nature, is clear; and that his name will for ever be held in grateful remembrance by all who cultivate physical science, and placed among those of its most eminent masters, is unquestionable. That he was a perfectly conscientious man in all the opinions which he embraced, and sincere in all he published respecting other subjects, appears equally beyond dispute. He was, also, upright and honourable in all his dealings, and justly beloved by his family and friends as a man spotless in all the relations of life. That he was governed in his public conduct by a temper too hot and irritable to be consistent either with his own dignity, or with an amiable deportment, may be freely admitted; and his want of self-command, and want of judgment in the practical affairs of life, was manifest above all in his controversial history; for he can be charged with no want of prudence in the management of his private concerns. His violence and irritability, too, seems equally to have been confined to his public life, for in private all have allowed him the praise of a mild and attractive demeanour; and we have just seen its great power in disarming the prejudices of his adversaries.

  I was intimately acquainted with Dr. Priestley: and a more amiable man never lived; he was all gentleness, kindness, and humility. He was once dining with me, when some one asked him (rather rudely) “How many books he had published?” He replied, “Many more, sir, than I should like to read.”

  A man of admirable simplicity, gentleness, and kindness of heart, united with great acuteness of intellect. I can never forget the impression produced on me by the serene expression of his countenance. He, indeed, seemed present with God by recollection and with man by cheerfulness.

  The sources of information concerning the life of Joseph Priestley are numerous and detailed. His philosophical writings, his theological controversies, his liberal political essays, his notable discoveries in chemistry, and even his misfortunes in the Birmingham riots of 1791, that caused his eventual expatriation, kept him constantly before the public. Being both affectionately admired and cordially hated, persecuted by his own townsmen yet highly esteemed by continental savants, bitterly assailed by the public press and yet the frequent recipient of substantial testimonials of esteem from active and influential friends, contemporary publications portrayed his acts, his opinions, and his remarkable talents. Since his death many men of letters have placed on record their estimate of Priestley’s philosophy, of his theological system, of his political tenets, and of his contributions to science, and, finally, every extended dictionary of biography and every encyclopædia, in three languages, for three-quarters of a century, has contained a sketch of his life and labors.

  His statue, modelled from Fuseli’s portrait, was placed in the Oxford Museum by a committee co-operating with Prince Albert; his name figures on the great frieze surrounding the Palais d’Industrie in the Champs Elysées; and Birmingham erected a statue to him in 1874, the centenary of the discovery of oxygen. When this statue was inaugurated, my mother, who was born in Pennsylvania, was probably the only person living in England who could personally recall Joseph Priestley. She was seven years old when he died. He had taught her to read, and her memory of him remained perfectly clear and vivid. The delicate features of the old man, framed in thin locks of silvery hair, are recorded in the portrait by Artaud before me as I write. This presentment, rather than any of those by Flaxman, is what my mother affirmed to be the real grandfather she remembered.

  He composed in shorthand; his rapid pen never left his meaning doubtful; a turn for epigram is the chief ornament of his style. He had little humour, but enjoyed a remarkable faculty for making the best of things. His home affections were strong. He provided a maintenance for his younger brother Joshua at Birstall. Domestic management he left to his wife, speaking of himself as a lodger in her house. To the faults of his memory he often alludes; it is curious that he never learned the American currency, and would say to a shopkeeper, “You will give me the proper change, for I do not know it.”… In person Priestley was slim but large-boned; his stature about five feet nine, and very erect. His countenance is best seen in profile, and the right and left profiles differ remarkably; the front face is heavy. He wore a wig till he settled in Northumberland, which did not boast of a hairdresser.

Scientific Work

  Gentlemen, it is with great satisfaction I enter upon this part of my office, to confer, in your name, the prize-medal of this year upon a member of this Society, so worthy of that distinction. It is with singular pleasure I acquaint you that the Rev. Joseph Priestley, Doctor of Laws, has been found at this time the best entitled to this public mark of your approbation, on account of the many curious and useful experiments contained in his “Observations on Different Kinds of Air,” read at the Society in March, 1772, and inserted in the last complete volume of your Transactions. And indeed, Gentlemen, when you reflect on the zeal which our worthy brother has shewn to serve the public, and to do credit to your Institution, by his numerous, learned, and valuable communications, you will, I imagine, be inclined to think that we have been rather slow than precipitate in acknowledging so much merit.

  He had great merit in the contrivance of his apparatus, which was simple and neat, to a degree that has never been equalled; and the indefatigable industry with which he pursued his researches, would entitle him to still higher praise, if he had combined with it the patience and forecast by which so much labour may be saved. The truth is, however, that he was always too much occupied with making experiments to have leisure, either to plan them beforehand with philosophical precision, or to combine their results afterwards into systematic conclusions. He was so impatient to be doing; that he could spare no time for thinking; and erroneously imagined, that science was to be forwarded rather by accumulating facts, than by meditating on those that were ascertained.

  Dr. Priestley drew no conclusion of the least value from his experiments. But Mr. Watt, after thoroughly weighing them, by careful comparison with other facts, arrived at the opinion that they proved the composition of water. This may justly be said to have been the discovery of that great truth in chemical science. I have examined the evidence, and am convinced that he was the first discoverer, in point of time, although it is very possible that Mr. Cavendish may have arrived at the same truth from his own experiments, without any knowledge of Mr. Watt’s earlier process of reasoning.

  Whose researches were devoted almost exclusively to the chemistry of the gases. Their results are recorded in six volumes of “Experiments and Observations on different kinds of Airs,” which were published between 1775 and 1786, and which appear to have enjoyed an uncommon degree of popularity. They are written in a light and agreeable style, detailing his successes and his failures with equal candour and openness, and laying open his entire chemical mind to the observation of his readers. He was very ingenious in devising experiments, and dexterous in his manipulations; and though the processes which he followed and the means which he had at his command were generally insufficient to secure that minute and rigorous accuracy which is equally necessary for the establishment of great truths and the exclusion of great errors, yet it may be safely asserted that few persons have contributed so great a number of valuable facts to the science of chemistry. He affected no profound philosophical views, and the character of his mind was altogether unequal to them; he generally adopted at once the most obvious conclusions which his experiments appeared to justify, and he modified or abandoned them upon further investigation with almost equal facility.

  Priestley’s reputation as a man of science rests upon his numerous and important contributions to the chemistry of gaseous bodies; and to form a just estimate of the value of his work—of the extent to which it advanced the knowledge of fact and the development of sound theoretical views—we must reflect what chemistry was in the first half of the eighteenth century…. It is a trying ordeal for any man to be compared with Black and Cavendish, and Priestley cannot be said to stand on their level. Nevertheless, his achievements are not only great in themselves, but truly wonderful, if we consider the disadvantages under which he laboured. Without the careful scientific training of Black, without the leisure and appliances secured by the wealth of Cavendish, he scaled the walls of science as so many Englishmen have done before and since his day; and trusting to mother wit to supply the place of training, and to ingenuity to create apparatus out of washing tubs, he discovered more new gases than all his predecessors put together had done. He laid the foundations of gas analysis; he discovered the complementary actions of animal and vegetable life upon the constituents of the atmosphere; and, finally, he crowned his work, this day one hundred years ago, by the discovery of that “pure dephlogisticated air” to which the French chemists subsequently gave the name of oxygen…. That Priestley’s contributions to the knowledge of chemical fact were of the greatest importance, and that they richly deserved all the praise that has been awarded to them is unquestionable; but it must, at the same time, be admitted that he had no comprehension of the deeper significance of his work; and, so far from contributing anything to the theory of the facts which he discovered, or assisting in their rational explanation, his influence to the end of his life was warmly exerted in favour of error.

  Priestley is mainly remembered by his theological controversies and his contributions to the history of pneumatic chemistry. I have nothing to tell you of his merits as a controversialist, except to say that some of his argumentative pieces are among the most forcible and best written of his literary productions. It is on his chemical work that his reputation will ultimately rest: this will continue to hand down his name when all traces of his other labours are lost. He has frequently been styled the Father of Pneumatic Chemistry; and although we may question the propriety of the appellation when we call to mind the labours of Van Helmont, of Boyle, and of Hales, there is no doubt that Priestley did more to extend our knowledge of gaseous bodies than any preceding or successive investigator…. The knowledge which Priestley, as he tells us, imparted to the French chemists was used by them with crushing effect against his favourite theory. The discovery of oxygen was the death blow to phlogiston. Here was the thing which had been groped for for years, and which many men had even stumbled over in the searching, but had never grasped. Priestley indeed grasped it, but he failed to see the magnitude and true importance of what he had found. It was far otherwise with Lavoisier. He at once recognised in Priestley’s new air the one fact needed to complete the overthrow of Stahl’s doctrine; and now every stronghold of phlogistonism was in turn made to yield. Priestley, however, never surrendered, even when nearly every phlogistian but he had given up the fight or gone over to the enemy. When age compelled him to leave his laboratory he continued to serve the old cause in his study, and almost his last publication was his “Doctrine of Phlogiston Established.”

  Foremost in the number of those who after Black distinguished themselves as pneumatic chemists, was Dr. J. Priestley. His first discovery, made in 1772, was nitric oxide gas, which he soon employed in the analysis of air…. Besides nitric oxide and nitrogen, Priestley first made known sulphurous acid gas, gaseous ammonia and hydrochloric acid, and carbon monoxide; and he it was who, by showing that the condition of ammoniacal gas and of common air is altered by the transmission of electric sparks, led to Berthollet’s analysis of ammonia, and Cavendish’s discovery of the composition of nitric acid.

  Priestley was just the man who was wanted in the early days of chemical science. By the vast number, variety and novelty of his experimental results, he astonished scientific men—he forcibly drew attention to the science in which he laboured so hard; by the brilliancy of some of his experiments he obliged chemists to admit that a new field of research was opened before them, and the instruments for the prosecution of this research were placed in their hands; and even by the unsatisfactoriness of his reasoning he drew attention to the difficulties and contradictions of the theories which then prevailed in chemistry. That the work of Priestley should bear full fruit it was necessary that a greater than he should interpret it, and should render definite that which Priestley had but vaguely shown to exist. The man who did this, and who in doing it really established chemistry as a science, was Lavoisier.

  Priestley’s eminent discoveries in chemistry were due to an extraordinary quickness and keenness of imagination combined with no mean logical ability and manipulative skill. But, owing mainly to lack of adequate training, he failed to apprehend the full or true value of his great results. Carelessness and haste, not want of critical power, led him, at the outset, to follow the retrograde view of Stahl rather than the method of Boyle, Black, and Cavendish. The modification of the physical properties of bodies by the hypothetical electricity doubtless led him to welcome the theory of a “phlogiston” which could similarly modify their chemical properties. Priestley was content to assign the same name to bodies with different properties, and to admit that two bodies with precisely the same properties, in other respects different in composition (“Considerations … on Phlogiston,” 1st edit. p., 17). Though often inaccurate, he was not incapable of performing exact quantitative experiments, but he was careless of their interpretation…. Priestley is unjust to himself in attributing most of his discoveries to chance.

General

  Of Dr. Priestley’s theological works, he (Johnson) remarked, that they tended to unsettle everything, and yet settled nothing.

  It is a mortifying proof of the infirmity of the human mind, in the highest improvement of its faculties in the present life, that such fallacies in reasoning, such misconstruction of authorities, such distorted views of facts and opinions, should be found in the writings of a man, to whom, of all men in the present age, some branches of the experimental sciences are the most indebted.

  The Bishop (Percy) wishes Mr. Pinkerton would carefully read Dr. Priestley’s “Institutes of Natural and Revealed Religion,” in 2 vols. 8vo, before he decides that all of that school have given up the Old Testament, as Mr. Pinkerton seems to hint in a former letter; but indeed he wishes Mr. Pinkerton would read them on other accounts.

  The religious tenets of Dr. Priestley appear to me erroneous in the extreme; but I should be sorry to suffer any difference of sentiment to diminish my sensibility to virtue, or my admiration of genius. From him the poisoned arrow will fall pointless. His enlightened and active mind, his unwearied assiduity, the extent of his researches, the light he has poured into almost every department of science, will be the admiration of that period, when the greater part of those who have favoured, or those who have opposed him will be alike forgotten.

  I do not wonder at Johnson’s displeasure when the name of Dr. Priestley was mentioned; for I know no writer who has been suffered to publish more pernicious doctrines. I shall instance only three. First, “Materialism;” by which mind is denied to human nature; which, if believed, must deprive us of every elevated principle. Secondly, “Necessity;” or the doctrine that every action, whether good or bad, is included in an unchangeable and unavoidable system; a notion utterly subversive of moral government. Thirdly, that we have no reason to think that the future world (which, as he is pleased to inform us, will be adapted to our merely improved nature), will be materially different from this; which, if believed, would sink wretched mortals into despair, as they could no longer hope for the “rest that remaineth for the people of God,” or for that happiness which is revealed to us as something beyond our present conceptions, but would feel themselves doomed to a continuation of the uneasy state under which they now groan. I say nothing of the petulant intemperance with which he dares to insult the venerable establishments of his country. As a specimen of his writings, I shall quote the following passage, which appears to me equally absurd and impious, and which might have been retorted upon him by the men who were prosecuted for burning his house…. My illustrious friend was particularly resolute in not giving countenance to men whose writings he considered as pernicious to society. I was present at Oxford when Dr. Price, even before he had rendered himself so generally obnoxious by his zeal for the French revolution, came into a company where Johnson was, who instantly left the room. Much more would he have reprobated Dr. Priestley. Whoever wishes to see the perfect delineation of this “Literary Jack of all Trades” may find it in an ingenious tract, entitled “A Small Whole-Length of Dr. Priestley,” printed for Rivingtons, in St. Paul’s Churchyard.

  Let Dr. Priestley be confuted where he is mistaken; let him be exposed where he is superficial; let him be repressed where he is dogmatical; let him be rebuked where he is censorious. But let not his attainments be depreciated, because they are numerous almost without parallel. Let not his talents be ridiculed, because they are superlatively great. Let not his morals be vilified, because they are correct without austerity, and exemplary without ostentation; because they present, even to common observers, the innocence of a hermit, and the simplicity of a patriarch; and because a philosophic eye will at once discover in them the deep-fixed root of virtuous principle, and the solid trunk of virtuous habit.

  In his “History of the Corruptions of Christianity,” Dr. Priestley threw down his two gauntlets to Bishop Hurd and Mr. Gibbon. I declined the challenge in a letter exhorting my opponent to enlighten the World by his philosophical discoveries, and to remember that the merit of his predecessor Servetus is now reduced to a single passage, which indicates the smaller circulation of the blood through the lungs, from and to the heart. Instead of listening to this friendly advice, the dauntless philosopher of Birmingham continues to fire away his double battery against those who believe too little and those who believe too much. From my replies he has nothing to hope or fear; but his Socinian shield has repeatedly been pierced by the spear of the mighty Horsley, and his trumpet of sedition may at length awaken the magistrates of a free country.

  I am at present re-re-reading Priestley’s Examination of the Scotch Doctors: how the rogue strings ’em up! three together! You have no doubt read that clear, strong, humorous, most entertaining piece of reasoning. If not, procure it, and be exquisitely amused. I wish I could get more of Priestley’s works.

  The attack of Dr. Priestley, however, gave him [Beattie] no concern. He appears, indeed, by his correspondence with his friends to have formed, at first, the resolution of replying to it; and he speaks as if he had already prepared his materials, and of being altogether in such a state of forwardness, and to be fully ready for the task. On farther consideration, however, he abandoned the idea, and he no doubt judged wisely. For, while Dr. Priestley’s “Examination” is now never heard of, the “Essay on Truth” remains a classical work, of the highest reputation and authority.

  Dr. Priestley has written more, we believe, and on a greater variety of subjects, than any other English author; and probably believed, as his friend Mr. Cooper appears to do at this moment, that his several publications were destined to make an æra in the respective branches of speculation to which they bore reference. We are not exactly of that opinion: But we think Dr. Priestley a person of no common magnitude in the history of English literature.

  No man living had a more affectionate respect for him. In religion, in politics, in physics, no man has rendered more service.

  His work [“Notes on all the Books of Scripture”] contains many invaluable notes and observations, particularly on the philosophy, natural history, geography, and chronology of the Scriptures; and to these subjects few men in Europe were better qualified to do justice.

  As to his theological creed, it could not justify the usage he received; for though he led the way to an open determined avowal of socinianism, no patron of liberty of conscience will impute this to him as a civil crime; nor should the friends of the orthodox creed condemn him for the frankness which rendered him the real, though unintentional friend of the truth, which has triumphed ever since Priestley tore the mask of concealment from error, and bade it be honest. The reflections which he poured upon evangelical sentiments, were often bitter enough, indeed; but the same may be said of the charges brought against him and his creed; and it was Horsley rather than Priestley, who enlisted the depraved passions of men, and the cruel prejudices of party politics, to contend in the arena, which should have been occupied solely by the authority of revelation, and the evidence of unimpassioned argument.

  The celebrated natural philosopher, Joseph Priestley, criticised at the same time both Hume and his antagonists. He may be said to have been more successful with the latter, whose instinctive principles he justly styled qualitates occultæ. In opposition to Hume he alleged a proof of the existence of the Divinity, which was untenable. He was a rank Determinist; and, consistently with his principles, controverted, as Hartley had done, the doctrine of free agency, and endeavoured to establish a system of materiality of the soul.

  Neglecting accordingly, all the presumptions for a future state, afforded by a comparison of the course of human affairs with the moral judgments and moral feelings of the human heart; and overlooking, with the same disdain, the presumptions arising from the narrow sphere of human knowledge, when compared with the indefinite improvement of which our intellectual powers seem to be susceptible, this acute but superficial writer attached himself exclusively to the old and hackneyed pneumatological argument; tacitly assuming as a principle, that the future prospects of man depend entirely on the determination of a physical problem, analogous to that which was then dividing chemists about the existence or non-existence of phlogiston. In the actual state of science, these speculations might well have been spared.

  Charmed with the discoveries of science, and eager, by prompt and unreserved communication, to diffuse as far as possible, their beneficial influence, he was yet supremely attracted to the discoveries of revelation. Hence his unvarying purpose, “by labour and patience, through evil report, and through good report,” and even when flesh and heart were failing, to promote, in the most enlarged sense of the expression, “the greatest good of the greatest number;” a sentiment with which he had the honour, by one of his earliest publications, to inspire that philosopher and philanthropist, who has lately left the world, after devoting himself in death, as in life, to its service; but whose memory will remain, unless, again, in the dispensations of an inscrutable Providence, “darkness shall cover the earth, and gross darkness the people.”

  There can be no doubt that versatility was the great characteristic of Dr. Priestley’s genius. Singularly quick of apprehension, he made all his acquisitions with facility and rapidity; and hence he derived a confidence in the working-power of his own mind, and a general faith in the sufficiency of the human faculties as instruments of knowledge, which led him on to achievement after achievement in the true spirit of intellectual enterprise.

  He is one of the most voluminous writers of any age or country, and probably he is of all voluminous writers the one who has the fewest readers.

  Priestley’s mind was objective to an extreme; he could fix his faith upon nothing, which had not the evidence of sense in some way or other impressed upon it. Science, morals, politics, philosophy, religion, all came to him under the type of the sensational. The most spiritual ideas were obliged to be cast into a material mould before they could commend themselves to his judgment or conscience. His intellect was rapid to extraordinary degree; he saw the bearings of a question according to his own principles at a glance, and embodied his thoughts in volumes whilst many other men would hardly have sketched out their plan. All this, though admirable in the man of action, was not the temperament to form the solid metaphysician, nay, it was precisely opposed to that deep reflective habit, that sinking into one’s own inmost consciousness, from which alone speculative philosophy can obtain light and advancement.

  Dr. Priestley’s metaphysical creed embraces four leading doctrines: he adopted the theory of vibrations, the association of ideas, the scheme of philosophical necessity, and the soul’s materiality. On all these topics he has furnished us with extended dissertations; and, whatever opinions may be ascertained of any or all of them, there are few persons but will readily admit the Doctor has displayed both great zeal and great ability in defence of them.

  His style is idiomatic, compact, incisive, and vigorous. He is eminently easy to follow; he usually describes the progress of his thoughts, explains by what circumstances he was led to take such and such a view, and thus introduces us from the known to the unknown by an easy gradation.

  Priestley possessed one of those restless intellects which are incapable of confining themselves to any single task, and, unfortunately, incapable in consequence of sounding the depths of any philosophical system. Urged partly by his natural bent, and partly, it may be, constrained by the pressure of poverty, he gave to the world a numerous series of dissertations which, with the exception of his scientific writings, bear the marks of hasty and superficial thought. As a man of science he has left his mark upon the intellectual history of the century; but, besides being a man of science, he aimed at being a metaphysician, a theologian, a politician, a classical scholar, and a historian. With an amazing intrepidity he plunged into tasks the effective performance of which would have demanded the labours of a lifetime. With the charge of thirty youths on his hands he proposes to write an ecclesiastical history, and soon afterwards observes that a fresh translation of the Old Testament would “not be a very formidable task.” He carried on all manner of controversies, upon their own ground, with Horsley and Bradcock, with his friend Price, with Beattie and the Scotch philosophers, with Gibbon and the sceptics, and yet often laboured for six hours a day at his chemical experiments. So discursive a thinker could hardly do much thorough work, nor really work out or co-ordinate his own opinions. Pushing rationalism to conclusions which shocked the orthodox, he yet retained the most puerile superstitions. He disbelieved in the inspiration of the Apostles, and found fault with St. Paul’s reasoning, but had full faith in the prophecies, and at a late period of his life expected the coming of Christ within twenty years. Nelson’s victories were to fulfil the predictions contained in the 19th chapter of Isaiah, and he suspected that Napoleon was the deliverer promised to Egypt. In his youth he had become convinced, as he tells us, of the falsity of the doctrines of the Atonement and the inspiration of the Bible, and “of all idea of supernatural interference except” (a singular exception!) “for the purpose of miracles.” Near half a century’s familiarity with theological speculation failed to emancipate his mind from the bondage of half-truths. It would be in vain, therefore, to anticipate any great force or originality in Priestley’s speculations. At best, he was a quick reflector of the current opinions of his time and class, and able to run up hasty theories of sufficient apparent stability to afford a temporary refuge amidst the storm of conflicting elements.

  If we choose one man as a type of the intellectual energy of the century, we could hardly find a better than Joseph Priestley, though his was not the greatest mind of the century. His versatility, eagerness, activity, and humanity; the immense range of his curiosity, in all things physical, moral, or social; his place in science, in theology, in philosophy, and in politics; his peculiar relation to the Revolution, and the pathetic story of his unmerited sufferings, may make him the hero of the eighteenth century.

  The style of this author is adequate to his thought. There is little flexibility or vivacity; the diction is heavy, and occasionally the preacher bestows on us the tediousness and prolixity too frequently associated with sermons. He has usually something to prove, and, if he does not prove it, the fault is not in the manner but in the matter of statement.

  His labours culminated in the “History of Early Opinions concerning Jesus Christ” (1786). Writing as a sectary, he damaged at the outset his claim to scrutinise in the scientific spirit the course of thought in Christian antiquity; but he was one of the first to open the way to the study of doctrinal development, and while proclaiming his own bias with rare frankness, he submitted his historical judgments to the arbitrament of further research. His account of the origin of Arianism, as a novel system, has stood the test. What was special in his method was the endeavour, discarding the speculations of the fathers, to penetrate to the mind of the common Christian people. He broke entirely with the old application of the principle of private judgment, maintaining that a purely modern interpretation of Scripture is, ipso facto, discredited, and the meaning attached to it by the earliest age, if ascertainable, must be decisive. A good summary of his position is in his “Letters” (1787) to Alexander Geddes the Roman catholic scholar, who had addressed him as his “fellow-disciple in Jesus.”