David Hume; portrait by Allan Ramsay, 1754

Edinburgh University Library, University of Edinburgh/Bridgeman Images

David Hume; portrait by Allan Ramsay, 1754

David Hume, who died in his native Edinburgh in 1776, has become something of a hero to academic philosophers. In 2009, he won first place in a large international poll of professors and graduate students who were asked to name the dead thinker with whom they most identified. The runners-up in this peculiar race were Aristotle and Kant. Hume beat them by a comfortable margin. Socrates only just made the top twenty.

This is quite a reversal of fortune for Hume, who failed in both of his attempts to get an academic job. In his own day, and into the nineteenth century, his philosophical writings were generally seen as perverse and destructive. Their goal was “to produce in the reader a complete distrust in his own faculties,” according to the Encyclopedia Britannica in 1815–1817. The best that could be said for Hume as a philosopher was that he provoked wiser thinkers to refute him in interesting ways. As a historian and essayist, though, Hume enjoyed almost immediate success. When James Boswell called him “the greatest Writer in Brittain”—this was in 1762, before Boswell transferred his allegiance to Dr. Johnson—he was thinking mainly of Hume’s History of England, which remained popular for much of the nineteenth century. “HUME (David), the Historian” is how the British Library rather conservatively still catalogued him in the 1980s.

Hume the philosopher did have his early admirers, but they had to be careful what they said about him. Six months after Hume’s death, one of his closest friends, Adam Smith, implicitly likened him to Socrates, which caused a scandal. Smith had recently published a controversial treatise on economics, The Wealth of Nations, yet his eulogy of Hume, and especially his account of Hume’s composure in the face of death, “brought upon me ten times more abuse than the very violent attack I had made upon the whole commercial system of Great Britain.” In a published account of his visit to the expiring Hume, Smith reported that he had found him making jokes about the underworld, apropos a satire of Lucian’s, and in good spirits, as usual:

Thus died our most excellent, and never-to-be-forgotten friend…. Upon the whole, I have always considered him, both in his lifetime, and since his death, as approaching as nearly to the idea of a perfectly wise and virtuous man, as perhaps the nature of human frailty will admit.

Educated readers of the time will have heard in Smith’s effusive words an echo of Plato’s encomium on the death of Socrates (“Such…was the end of our comrade, who was…of all those whom we knew…the bravest and also the wisest and most upright man”). The problem was that Hume was widely known to have been some sort of infidel. He was therefore clearly a reprehensible fellow, albeit a jovial one, and thus undeserving of a calm death, let alone of tacit comparisons to Socrates.

As James Harris drily notes in his fine new biography, Hume’s private letters show that “he was not very good at being serious about religion.” His lack of piety and the decorously veiled attacks on theism in his published writings may play some part in his current academic popularity. Most professional philosophers today are atheists—73 percent of them, according to the 2009 survey. Perhaps Hume’s cheerful wit and enjoyment of life also help to make him a model for today’s philosophers, who do not like to think of themselves as unduly serious when off-duty. When he lived in Paris in his early fifties, the famously equable and entertaining Hume was celebrated in the salons as le bon David. A plausible report in a London newspaper quoted him as declining his publisher’s requests for further volumes of his profitable History on the grounds that he was now “too old, too fat, too lazy, and too rich.”

Still, it is probably the rise of so-called “naturalism” in philosophy that best explains Hume’s newfound appeal. Naturalism has several components, all of which were prominent in his work. Hume stressed the similarities between people and other animals: a century before Darwin’s Descent of Man, he argued that there is no great difference between the minds of humans and the minds of some creatures in zoos. (Hume also anticipated Darwin in implying that certain mental traits function to aid reproduction.) He treated religion as a natural phenomenon, to be explained in psychological and historical terms—which tended to annoy the pious—and he argued that the study of the mind and of morals should be pursued by the same empirical methods that were starting to cast new light on the rest of nature. Philosophy, for Hume, was thus not fundamentally different from science. This outlook is much more common in our time than it was in his.


Philosophers now regard Hume’s account of reason not as a mischievous plot to undermine it but as an attempt to explain how it works. As Harris puts the matter, he was developing “an entirely new theory of rationality.” Hume treats humans as clever animals whose beliefs about most things are based on “custom,” in the form of a propensity to expect the future to resemble the past—a propensity, he argued, that is essential for the conduct of life, but cannot be provided with any sort of independent justification. This thesis has come to be known as “the problem of induction,” though Hume himself did not regard it as presenting much of a problem. He played up the importance of what he called “experimental” or “probable” reasoning in human knowledge, and played down the significance of mathematical and quasi-mathematical deductions. This was a considerable novelty after some two thousand years in which philosophers, still enthralled by Greek geometry, had mostly done the opposite. Hume’s emphasis on the sort of empirical and fallible beliefs that humans share with some lesser creatures was all too easily interpreted as a denigration of the powers of the human mind.

Hume first advanced his new theory of rationality in A Treatise of Human Nature, most of which was written by the time he was twenty-six, and which was, he claimed, mapped out while he was still a teenager. When the Treatise did not produce quite the philosophical revolution that he had been counting on, Hume blamed its failure mainly on the way he had expressed himself, not on the book’s main ideas. He then set out to find other ways to communicate them, and other literary projects to pursue.

Hume’s life may therefore seem to have been a drama in two very different acts. In the first, he tried unsuccessfully to make his mark in philosophy. In the second, he produced lighter works in order to make money and become famous. Hume the philosopher thus became Hume the popular historian and essayist.

But is that the best way to see his career? Did Hume dilute his ideas to make them more appealing to “the habitués of coffee-houses,” as one of his nineteenth-century editors sniffily suggested? And was it fair of another to claim that “few men of letters have been at heart so vain and greedy of fame”? Harris’s biography argues that there was more continuity and integrity to Hume’s intellectual journey than such remarks suggest. A love of literature had always been his “ruling passion,” wrote Hume at the end of his life, and as Harris points out, “literature” was a broad concept in Hume’s century. It covered the entire world of learning, including history, divinity, philosophy, and politics. Hume always saw himself as a “man of letters,” unconfined by any particular academic specialty, and the range of his interests was evident from the start. Eighteenth-century Scotland, with its four thriving universities and a plethora of discussion clubs, was the perfect place for such polymathy.

Hume’s Treatise was conceived as a work in five parts, dealing with the understanding, the passions, morals, politics, and the arts, all of which were to be illuminated by a new, empirical science of human nature. According to the young Hume, the reason why so little had been established in these branches of learning was that they had hitherto depended “more upon Invention than Experience.” Careful observation of how the mind actually works—of how thoughts and feelings arise, and give rise to further thoughts and feelings—would provide “a compleat system…built on a foundation almost entirely new, and the only one upon which they can stand with any security.”

The first two parts of Hume’s Treatise, dealing with the understanding and the passions, were published at the start of 1739, when he was twenty-seven, and were followed the next year by a third, dealing with morals. The parts on politics and the arts never appeared, because Hume soon judged the project to have been a failure. The Treatise, he wrote in an autobiographical essay, “fell dead-born from the press, without reaching such distinction as even to excite a murmur from the zealots.”

This was an exaggeration. Not only had the Treatise been fairly widely and promptly reviewed, but the zealots murmured against it loudly enough for him to issue an anonymous pamphlet defending it against various charges. These charges were, among other things, that the Treatise advocated “Universal Scepticism,” and that it sapped “the Foundations of Morality, by denying the natural and essential Difference betwixt Right and Wrong,” all of which sounded rather impious.

Hume’s response to the allegation of universal skepticism was that the author of the Treatise—who, he pretended, was someone else—had meant only “to abate the Pride of mere human Reasoners.” He advocated “Modesty…and Humility, with regard to the Operations of our natural Faculties.” As for the foundations of morality, Hume anonymously protested that the author of the Treatise had merely denied that “the Propositions of Morality were of the same Nature with the Truths of Mathematicks and the abstract Sciences.” The book did not dispute the fact that there was a difference between right and wrong; rather it maintained that this difference reflects humanity’s “internal Tastes and Sentiments”—which, according to Hume’s pamphlet, ought not to be received as a shocking idea.


Denis Diderot
Denis Diderot; drawing by David Levine

The Treatise had itself been published anonymously, which was not unusual for controversial works by new authors. It was no real secret who had written it, though. Anonymity in such cases was as much a conventional expression of modesty as an attempt to escape the consequences of censure. But the first time Hume acknowledged in print that he was in fact the author of the Treatise was when he emphatically disowned it as juvenilia. Almost as soon as he had published it, Hume rued the fact that he had rushed into print too early. He omitted the Treatise from editions of his collected writings and begged the public to judge him only by his other works.

Readers of his philosophy have, on the whole, ignored this request. That is a pity, because Hume’s distinctive doctrines about the mind and the limits of human knowledge emerge more clearly in a set of linked essays that he published in his late thirties. These essays (which are now known as his Enquiry Concerning Human Understanding) are more streamlined and carefully argued than the corresponding part of his Treatise. This new version of his philosophy omitted the Treatise’s tangled material on the ideas of space and time, and its treatment of the idea of the self, which Hume quickly came to see as “very defective.” Hume’s mature work also clarified his position on the relation between reason and passion. Reason, he wrote, is itself “nothing but a general and a calm passion, which takes a comprehensive and a distant view of its object.” Mastering one’s passions was therefore not, as he had misleadingly made it sound in the Treatise, a contest between reason on the one hand and passion on the other. It was a matter of making one’s passions milder and less agitated.

Far from being a watered-down presentation of his fundamental ideas, the new essays were in several respects bolder than the Treatise. For one thing, they made the antireligious implications of his thought more explicit, though they did so with tact. Hume included in the essays a discussion of miracles that he had omitted from the Treatise. This discussion drew on his analysis of probabilistic reasoning to argue that reports of religious miracles should always be disbelieved. He also argued that the ever-popular “design argument,” which infers the existence of God from apparent signs of intelligent design in nature, jumped to an unwarranted conclusion.

As always, Hume presented his impious ideas as if they were directed only against “false religion,” not the vague “true religion” to which, for the sake of decorum, he feigned adherence. The enemy, he pretended, was superstition and “enthusiasm”—that is, zealotry—not religious faith itself. Hume placed several layers of insulation between himself and his attack on the design argument. He put his subversive ideas in the mouth of an unnamed friend, who purported to be making a speech on behalf of Epicurus, and with whom Hume pretended to disagree.

In the years between the Treatise and the Enquiry Concerning Human Understanding, Hume published two volumes of political, literary, and miscellaneous essays that can to some extent be seen as substitutes for the abandoned portions of the Treatise, though Hume no longer presented his efforts as part of “a compleat system.” The essays brought him some renown as a man of letters, and a job as tutor and companion to one of their admirers, the Marquess of Annandale, who turned out to be mad. After the marquess dismissed him in a tantrum, and Hume heard that his application for a chair in philosophy had been turned down, he took up an offer to join a distant relation on a military expedition. The mission was originally aimed at Quebec, but ended up in Brittany, and was somewhat farcical. Voltaire ridiculed it in one of his historical works. But it afforded Hume time to write the Enquiry, which was followed three years later by a similar set of interconnected essays, An Enquiry Concerning the Principles of Morals.

This second Enquiry was, in Hume’s view, “incomparably the best” of his works, but the public, in both Britain and France, was more taken by his Political Discourses, a set of essays mostly on economic topics that followed a year later in 1752. Adam Smith wrote that Hume was, so far as he knew, the first writer to argue that manufacturing and commerce tend gradually to produce greater liberty and security for citizens. Hume’s economic essays were particularly acute on monetary theory and on trade. He was insistent about the mutual benefits of international trade, wary of national indebtedness, and dismissive of mercantilist obsessions with gold. It has been said that if only Hume had laid out his arguments more systematically, the birth of modern economics would be recorded as 1752, instead of 1776, when Smith’s Wealth of Nations was published.

Harris skillfully explores the background of Hume’s economic and other essays, and indeed all of his works, describing in some depth the debates to which they contributed and the influences of Hume’s own reading, especially of Bernard Mandeville, Frances Hutcheson, Pierre Bayle, and Cicero. Surprising as it may seem, Harris’s book does appear to be, as he claims, the first intellectual biography of Hume. As he acknowledges, readers who are primarily interested in Hume’s life should start with the biography by a late American scholar, Ernest Campbell Mossner, which was first published in 1954. Mossner’s life of Hume is suffused with an affection for its subject that, according to Harris, sometimes obstructs a “properly dispassionate” examination of the facts.

This, arguably, is a price worth paying in Mossner’s case. Admirers of le bon David may want a little more enthusiasm, in the contemporary sense of the word, than Harris can muster. But he deserves the gratitude of Hume scholars for a unique achievement. No other work takes such pains to elucidate all of Hume’s multifarious writings, including his History of England, and to present an account of his literary career as a consistent if not unified whole.

Hume had been toying for some time with the notion of writing a history, but did not begin in earnest until he was put in charge of the sizable library of the Faculty of Advocates in Edinburgh in 1752. After a few words on the “rude and turbulent” ancient Britons and their appalling Druids, his six-volume History traces England’s story from the arrival of Caesar to the deposition of James II in 1688. The inhumane effects of religious zealotry are a recurring theme. Hume’s emphasis on the harms to which religion can all too easily lead did not please many clerics. Harris argues that Hume’s History should be reckoned as broadly philosophical because of its focus on general principles of social, economic, and political change rather than on the actions of individuals. It was sometimes judged—for instance by Dr. Johnson, who did not intend this as a compliment—to be similar to the histories of Voltaire.

Voltaire himself praised Hume for transcending the partisanship of previous histories in English. Hume was neither a royalist nor a parliamentarian, wrote Voltaire, but “un homme équitable.” Harris shows how true this was, though readers will find that unless they are particularly interested in where Hume stood in relation to Whig versus Tory ways of looking at the Glorious Revolution of 1688, there will sometimes be more detail than they need.

Hume and Voltaire never met. By the time Hume moved to Paris in 1763, to work at the British embassy, Voltaire had mostly retired to his country estate. Hume became close to Diderot and d’Alembert, the two editors of the French Enlightenment’s Encyclopédie, and spent time in the salons of his intimate friend the Comtesse de Boufflers and of the materialist Baron d’Holbach, who was more or less openly an atheist. The unbelief of d’Holbach and some members of his circle was too dogmatic and zealous for Hume’s taste; they, in turn, seem to have found his variety of irreligion a little mild.

Another British visitor to d’Holbach’s salon, Hume’s young admirer Edward Gibbon, reported that they “laughed at the scepticism of Hume,” though this seems to have been a good-tempered affair. By “scepticism” Gibbon meant what would now be called “agnosticism.” The principles of Hume’s philosophy implied that the question of God’s existence cannot be settled definitively either way, so he was in one sense an agnostic. However, since he does not seem to have entertained any belief in God, it is probably also fair to call him an atheist—just not a campaigning one.

A distinctive quality of Hume’s writings on religion is that he sought gently to persuade rather than to confront. He was careful to observe the line that divided authors whose writings were disapproved of but tolerated and those whose books could not be permitted in one’s house. In order to avoid relegation to the latter class of writers, whose works would have fewer opportunities to persuade, it was enough to adopt the semblance of piety. It didn’t matter too much if some readers were wise to your game.

Hume played this game most ingeniously in his posthumous Dialogues Concerning Natural Religion (1779), to which he was making alterations in the final weeks of his life. Several friends who saw the manuscript, including Adam Smith, thought that it went too far, and urged him not to let it be published even after his death, presumably for fear that it would ruin his reputation and make his other works less likely to be read. Seeking to reassure Smith, who he hoped would undertake its posthumous publication, Hume told him that nothing could be “more cautiously and more artfully written.”

The manuscript was indeed so artfully written that people who are unfamiliar with eighteenth-century conventions of “theological lying,” as it has been called, still sometimes think that Hume ended up endorsing the idea that design in nature points to the existence of a God.* In his Dialogues, which were closely modeled on a work by Cicero, Hume expanded and refined the criticisms he had earlier attributed to a fictitious Epicurean friend, this time putting them in the mouth of a character named Philo, whom the narrator of the Dialogues presents as having lost the debate. Philo concludes by allowing that “the cause or causes of order in the universe probably bear some remote analogy to human intelligence,” which sounds respectably like an endorsement of theism. But careful readers will notice that the analogy conceded by Philo is demonstrated to be so remote that it is in fact consistent with atheism. Hume once remarked in a letter to the Comtesse de Boufflers that poor Rousseau had got into trouble because he neglected to “throw any veil over his sentiments.” This was not a mistake Hume was inclined to make, even posthumously.

When he returned to Britain from Paris in 1766, Hume took Rousseau with him, offering to help him find refuge and obtain a royal pension. D’Holbach warned Hume that this was unwise, since Rousseau had a habit of biting the hand that fed him. Hume’s kindness was indeed ill repaid. Rousseau was at this stage stumbling in a no-man’s-land between sanity and madness, and soon publicly accused Hume of having plotted against him. Hume was horrified and decided to publish his side of the sorry tale. Harris takes him to task for this. Hume, he writes, should have weathered Rousseau’s calumny, and adopted “a more objective and compassionate attitude towards [Rousseau’s] obviously tortured state of mind.” This is surely asking rather a lot of le bon David. As even Adam Smith acknowledged, Hume’s virtues went only so far as “the nature of human frailty will admit.”