Two years ago, Dennis Rasmussen published a book that he says “was an absolute joy to write” and indeed is a joy to read: The Infidel and the Professor. It is the biography of a “Friendship That Shaped Modern Thought”, as the subtitle explains. This deceptively anecdotal story of how David Hume and Adam Smith became the fastest of friends over the years allows Rasmussen to throw new light on their epoch-making contributions to the science of society.
For more by Dennis Rasmussen, see his discussion of this book at “The Infidel and the Professor: The Friendship of Adam Smith and David Hume,” by Dennis Rasmussen at AdamSmithWorks.org, Sep 1, 2018.

Also see the EconTalk podcast episode Dennis Rasmussen on Hume and Smith and The Infidel and the Professor, November 6, 2017.

See also the video at Dennis Rasmussen AMA [Ask Me Anything]: The Infidel and the Professor. YouTube, September 4, 2019.

Smith and Hume probably met in 1749. Smith had come down from his six years at Oxford where he had read Hume’s Treatise, much to the scandal of the Balliol College authorities. He was asked by Lord Kames to give a series of lectures on Rhetoric and Belles Lettres in Edinburgh. Hume may have attended the second set of those lectures and, from later remarks, must have been impressed by Smith’s delivery and content. Smith was greatly admired for his pure English when compared with the Scottish voices of his compatriots who had not studied south of the border. He also shone with practical erudition in his analysis of Greek and Roman eloquence. Such was the starting point of the friendship. Recalling the many years that it lasted allows Rasmussen to discover for us hidden dimensions of their personalities and their thought, which were a revelation at least for this reader who believed he knew his Adam Smith well and his David Hume pretty well.

The two friends were very different people. Hume always saw the good side of life. Ever an optimist, he was full of fun even when circumstances were not propitious. The reader of these parallel lives will be surprised to discover that in his more prosperous later years in Edinburgh he cooked meals for his guests from recipes he had learnt during his time in Paris. The famous letter he wrote to Smith on the reception of The Theory of Moral Sentiments in 1759 deserves Rasmussen’s praise of it “as one of the most charming letters in the entire history of philosophy.” The playful humour of Hume must have amused Smith, despite his more restrained manner.

Their attitudes and writings on religion bring out that contrast best. Hume almost welcomed the tempestuous reception of his books and essays where he argued for his religious infidelity. Smith was much more careful of “his own quiet”, as became clear from his advice to Hume that Dialogues Concerning Natural Religion (later published by Hume’s nephew in 1779) should remain unpublished—a piece of advice also given by other friends. This did not mean that Smith was showing a lack of courage, for in the letter he wrote after Hume’s death to William Strahan, the publisher of both writers, he extolled the character of his friend “as approaching as nearly to the idea of a perfectly wise and virtuous man, as perhaps the nature of human frailty will permit”. Smith’s words of praise for an infidel deeply shocked religious opinion, but he never took them back.

Differences between Hume and Smith

Rasmussen, with his light manner, has much to say on Smith’s and Hume’s doctrines in matters of rhetoric, ethics, and the sociology of capitalism.

Adam Smith’s Lecture on Rhetoric at Glasgow were among the manuscripts he had burned just before he died; luckily, for us two students had kept very detailed notes of his course, as also happened with his Lectures on Jurisprudence. One can guess what impressed Hume in those Edinburgh lectures, though the art of speaking and writing does not receive today the same kind of detailed attention as in the 18th century. Adam Smith’s use of examples from classical Greece and Rome make reading difficult for people not familiar with classical languages and literature. Rhetoric has morphed into public relations and, with the help of the new communication technology, has a much wider (though less refined) economic and political presence in society. What interests us now is the confirmation the lecture notes afford of Smith’s ability as a lecturer, well noted by his contemporaries. Also, we are surprised by complaints at the time that the prose of the Wealth of Nations was inelegant in contrast with his other writings.1 This is an early example of the barrier that economics encounters from the use of the long chains of abstract reasoning typical of our speciality.

“Neither [Hume nor Smith] thought that ethics was a product of reason; both thought it was a social phenomenon resulting in ‘sentiment’.”

One of the points that Rasmussen illuminates is the differences in the ethical theories of Hume and Smith. Neither thought that ethics was a product of reason; both thought it was a social phenomenon resulting in ‘sentiment’. However, Hume’s ethical theory was what later would be called utilitarian: moral approbation had its origin in what was convenient for the survival of society. Smith’s theory was more individualistic: the fountain of social rules and people’s approval or disapproval was an innate feeling of sympathy for one’s fellow men. The opening phrase of The Theory of Moral Sentiments is justly famous:

  • How selfish soever man may be supposed, there are evidently some principles in his nature, which interest him in the fortune of others, and render their happiness necessary to him, though he derives from it nothing but the pleasure of seeing it.

As Dugald Stewart underlined in 1793, Smith felt that the sentiment of the utility of a moral rule could enliven the obedience to its precepts but was not “the principal source of moral approbation” (Stewart, page 29).

More fundamentally, Hume and Smith differed in the nature of ‘sympathy’ from which moral sentiments flowed. For Hume, Rasmussen says, feeling sympathy with other persons is “a kind of emotional contagion,” or involuntary vibration. For Smith, sympathy would better be described as empathy. Depending on what we find when we ‘enter’ the sentiments of another person, we may end disapproving of their sentiments if the anger, let us say, is unjustified. (Rasmussen, 90-94)

A third difference between the two friends is underlined by Rasmussen in chapter nine of the book. It concerns their attitude towards the kind of commercial society that was growing before their eyes, or, as we say today, their attitude to ‘capitalism’. Of course, Smith fully agreed with Hume on commerce not only being the fountain of prosperity but also of “virtue, liberty, civility, knowledge, and happiness” (169). They concurred when relating the dissolving effect of commerce on feudal society, and when maintaining that the prosperity of neighbouring countries was to be wished for (or prayed for, said Hume) to secure the well-being of one’s own country. Hume did see dangers in commercial societies, especially the temptation of colonial adventures and the accumulation of debt. Smith agreed on both counts. Both defended American independence. Excessive public debt was an immediate menace under the gold standard, but this is true even with today’s fiat currencies for its effects on long-term inflation. But Smith went unexpectedly further when underlining the possible drawbacks of a commercial society. While Hume welcomed its toil and trouble, Smith lamented the pursuit of the baubles of wealth that characterise commercial society. And more radically, the division of labour, the main cause of the wealth of nations for Smith, tended to maim the spirit of ordinary workers and make them unfit for the defence of the country.

Still, both Hume and Smith saw the progress of commerce and manufacture as the principal force for the establishment of “order and good government, and with them, the liberty and security of individuals” (Wealth of Nations book 3, as quoted by Rasmussen, page 162). The fact that, as Rasmussen underlines, “neither Hume nor Smith was a free market absolutist” (168) does not detract from their contribution to the epoch-making change of Western society the 18th century. They thought government was necessary to guarantee order and, explicitly in the case of Smith, to ensure national defence, the Courts of Law, and the construction of public works: or, as Smith put it, “peace, easy taxes, and a tolerable administration of justice”. But they both rejected attempts of politicians to try to promote national prosperity or to defend special interests.

Smith at the Customs House

The fact that Smith actively sought the position of Commissioner of the Scottish Customs and performed it during the last twelve years of his life, from 1778 to 1790, has been a cause of surprise and even scandal for his followers. The problem is that the duties charged by the Customs of the United Kingdom were a fundamental instrument of the mercantilist policy that Smith so clamorously opposed. Rasmussen argues that “Smith was not simply opposed to all tariffs […]. He opposed using them as an instrument of monopoly or as a means of favouring domestic industries over imports” (229). Tariffs were an important source of funds for the state. And his father had been a customs officer in Kirkcaldy.

Still, doubts persist as to why he sought the position. Gary Anderson et al. (1985) have made a careful study of the activity of the Scottish Custom Board during Smith’s tenure. Their conclusion is that Smith did not behave as if the post were a sinecure. Four meetings a week and full attention to complicated and varied business was not the behaviour of an economist bent on streamlining or even lightening the mercantilist regulations of the Scottish Customs. In that post Smith was “a hard-nosed bureaucrat”, “not a radical reformer who transformed the service” in accordance with his anti-mercantilist doctrine. No echo of his work at the Customs can be heard in the last revised editions of the Wealth of Nations in 1784. Perhaps, as Stigler is reported to have said, Smith was tired of economics. In those final years, he put all his effort into revising and adding to The Theory of Moral Sentiments for the 1790 edition. He also read to the Literary Society of Glasgow some of the Essays on Philosophical Subjects published after his death in 1795. So, he was fully occupied without turning his attention to his experience at the Custom Board.

Smith, Hume, and Darwin on the ethics of social life

Adam Smith starts Moral Sentiments by noting that “there are evidently some principles in [man’s] nature which interest him in the fortune of others”. Though he confirms this with various examples, he does not explain the origin of, or reason for, this natural trait. This is what Charles Darwin tried to supply in The Descent of Man and Selection in Relation to Sex (1871). He started chapter III by declaring that “of all the differences between man and the lower animals, the moral sense or conscience is by far the most important”; and that, as far as he knew, “no one had approached it exclusively from the side of natural history”.

Note that Adam Smith wrote before Charles Darwin and influenced Darwin’s writings. See the EconTalk podcast episode Russ Roberts and Mike Munger on How Adam Smith Can Change Your Life.

Interestingly, Darwin presented a theory of ethics quite similar to that of Hume who mostly based moral sentiments on general utility. His main explanation for the evolution of social norms is that they have “certainly been developed for the general good of the community”.

  • The term, general good, may be defined as the means by which the greatest possible number of individuals can be reared in full vigour and health, with all their faculties perfect, under the conditions to which they are exposed.

He did separate this definition from that of the political utilitarians of the 19th century, by underlining the internalisation of social norms: “… the general good or welfare of the community, rather than the general happiness.” The steps by which a moral sense evolved in any animal “with well-marked social instincts” were the following. Firstly, an animal would take pleasure in communing with its fellows thus develop a feeling of sympathy with them. Secondly, it would remember and feel dissatisfaction when it had allowed a passing need to overpower social instinct. Thirdly, the ability to speak, once acquired, would reinforce the expression of common opinion. Finally, habit would strengthen the sway of communal behaviour.

As Rasmussen notes (98-9), Hume did himself little good when he excessively stressed that utility is “a foundation of the chief part of morals”, somewhat passing over agreeableness as another quality contributing to moral approval. Be that as it may, Smith cast his net wider than the utility of the group when explaining ethical norms. Merit and demerit depend on the intended or realised effects of actions, to which Smith allowed a role in moral sentiments. But what Smith calls ‘propriety’ depended on the quality of actions in themselves, as judged by the impartial spectator we carry in our breast. In our time we would judge in favor of the propriety of the captain of the Titanic choosing to sink with his ship, for the utility of no one but as a demonstration of the proper thing to do.

Later advances in biology have deepened Darwin’s explanations and made them less mechanistic, so to speak. Ants and bees sacrifice themselves for their hive or heap because they are sisters. We men trade with strangers and extend our moral attitudes to individuals who do not belong to our tribe.

Hume’s razor

One last question remains to be discussed. I call it “Hume’s Razor” because it reminds me of Occam’s razor: the injunction that Entia non sunt multiplicanda praeter necessitate, (explanatory assumptions should not be multiplied unnecessarily). In this case this is the caveat formulated (irony of ironies) by Hume, that it is illogical to go from propositions with the verb is to injunctions with the verb ought. It would seem, then, that Hume and Smith and Darwin should have used a razor to cut ethical prescriptions loose from social psychology or evolutionary theory. Should one not refrain from deducing ethical rules from factual evidence? What is the logical connection between morality and the observation of human sentiments or of natural evolution? Should one disobey Hume the logician and follow Smith in discriminating among values by looking at their consequences? I will leave these difficult questions for another day.


[1] “… [h]is own didactic style in his last famous book [The Wealth of Nations] (however suited to the subject)—the style of the former book [Moral Sentiments] was much superior—was certainly not a model of good writing…”. James Wodrow to the Earl of Buchan, after 1776. Introduction to Lectures on Rhetoric and Belles Lettres, 11. OUP, 1983.


Gary M. Anderson, William F. Shughart II, and Robert D. Tollison (1985): “Adam Smith in the Customhouse”. Journal of Political Economy, Vol. 93, No. 4 (August), pp. 740-759.

Isaiah Berlin (1965): The Roots of Romanticism. The A.W. Mellon Lectures in the Fine Arts. Pimlico.

Charles Darwin (1871): The Descent of Man and Selection in Relation to Sex. As seen in id. Evolutionary Writings. James A. Secord editor. Oxford 2008.

David Hume (1734): Treatise of Human Nature. L.A. Selby-Bigge, ed. (1896). On Line Library of Liberty, Liberty Fund, Indianapolis.

Immanuel Kant (1788): Die Kritik der Practiche Vernunft. (Accessed in the Spanish translation of E. Miñana Villagrasa and M. Garcia Morente, 1913. Austral, 1975.)

Dennis C. Rasmussen (2017): The Infidel and the Professor. David Hume, Adam Smith, and the Friendship that Shaped Modern Thought. Princeton.

Donald S. Rasmussen and Donald Den Uyl (1998): Liberalism Defended. The Challenge of Post-Modernity. Edward Elgar.

Adam Smith (1759, 1790): The Theory of Moral Sentiments. D.D. Raphael and A.L. MacFie, editors. Oxford, 1976.

Adam Smith (1776): An Inquiry into the Nature and Causes of the Wealth of Nations. R.H. Campbell and A.S. Skinner, editors. Oxford, 1976.

*Pedro Schwartz is “Rafael del Pino” Research Professor of economics at Universidad Camilo José in Madrid. A member of the Royal Academy of Moral and Political Sciences in Madrid, he is a frequent contributor to the European media on the current financial and social scene. He was a past President of the Mont Pelerin Society.

For more articles by Pedro Schwartz, see the Archive.