The year of our Lord 2023 was the tercentenary of Adam Smith’s 1723 birth. That would seem an apt occasion to reevaluate Smith’s contributions, and a quick internet search will discover indeed many conferences, books, and articles that have marked the occasion by examining, or reexamining, various aspects of Smith’s thought. Smith continues to be cited in both academic and popular literature, by professors as well as pundits—often, it must be acknowledged, in support of seemingly inconsistent aims. People across various economic, philosophical, and political spectrums apparently continue to find value in claiming Smith as an authority. What is also often apparent is that many who cite Smith have not actually read Smith—beyond, perhaps, the quote or two they found online. Like the Bible, Smith’s work is frequently cited but infrequently read.

For good or ill, then, Smith thus continues to loom large in economic and policy debates. One continuing argument regards who are the real heirs of Smith’s thought: Milton Friedman and the free-market-oriented Chicago school of economics, or the progressive critics of capitalism? It turns out, then, that Smith’s influence is not merely historical. But that is not only because people still debate his legacy. Unlike many other influential figures from the past, Smith actually got many things right.

A few days before Smith died in 1790, he summoned two of his friends—the chemist Joseph Black (1728–99) and the geologist James Hutton (1726–97)—and asked them to burn his unpublished manuscripts, on the grounds that they were insufficiently perfected to meet Smith’s exacting standards. Smith had apparently made this request before, but Black and Hutton had resisted; this time, however, Smith insisted. Black and Hutton hence grudgingly burned 16 volumes of Smith’s handwritten manuscripts. We cannot be sure what exactly was destroyed in that tragic conflagration, but the result is that Smith’s enduring contributions are contained in his surviving two books and a handful of essays.

The two books are The Theory of Moral Sentiments (TMS), first published in 1759; and An Inquiry into the Nature and Causes of the Wealth of Nations, first published in 1776. Today, Wealth of Nations is far better known, but it was his Theory of Moral Sentiments that first brought Smith renown, both in Britain and on the European continent. It was widely studied by his contemporaries and successors. After having read TMS, Immanuel Kant (1724–1804), for example, referred to Smith as his “Liebling,” or favorite. A century later, Charles Darwin (1809–82), in his 1871 Descent of Man, would refer to Smith’s “striking” claims in TMS. It was on the strength of Smith’s lectures that eventually became TMS that Smith was invited to assume the position of Professor of Logic in 1751 and then Professor of Moral Philosophy in 1752 at the University of Glasgow (at the tender ages of 28 and 29, respectively).

Why did TMS achieve such notoriety? It is a brilliant investigation into what we might today call rather “moral psychology” than “moral philosophy,” and it thereby was at the forefront of a new school of moral inquiry. Unlike most treatises of moral thought before and in Smith’s day, TMS is not primarily a book of “moralism,” telling us what we ought, or ought not, to do. Instead, it attempts to answer two primary questions: first, where do our moral sentiments come from, and, relatedly, how do we arrive at them? Second, why is there so much overlap between individuals’ moral sentiments and those of their communities as well as overlap among various communities’ own moral sentiments? These are empirical questions, and Smith’s attempt to describe the process of human moral judgment-making has proven remarkably prescient.

Smith offers a developmental account of moral sentiments, one based on what he calls our natural desire for “mutual sympathy” of sentiments (TMS, 1.1.2.1* and passim). Of the many empirical claims Smith makes about human psychology, this is perhaps the most crucial. All human beings, Smith believes, desire to see their sentiments echoed, or reflected, in others: “Nothing pleases us more than to observe in other men a fellow-feeling with all the emotions of our own breast” (1.1.2.1). Smith uses “sympathy” in its etymological sense of “feeling with” (1.1.1.4): we find it pleasurable when we see that our sentiments, whatever they are, are reflected in others, just as we find it unpleasant when we find that others’ sentiments depart from ours. This sense is heightened as we proceed from matters of indifference or of little moment to us, to matters that concern us more deeply. Similarly, the sentiments of those about whom we care a great deal matter more to us than do the sentiments of those about whom we care little, or whom we do not know. So if politics matters much to me, then Smith’s prediction is that I will seek out the company of others who share my interest in politics—that is, people with whom I can share a “sympathy” of sentiments about politics. If music matters to me, I will seek out the company of others with whom I can share a sympathy of sentiments about music; and so on, regarding literature, philosophy, movies, and even video games.

The desire for “the pleasure of mutual sympathy” of sentiments thus acts as something like a centripetal societal force. It draws people of similar sensibilities together, even as it draws them away from those with whom they have an “antipathy” (2.1.5.4) of sentiments.

According to Smith, the desire for mutual sympathy of sentiments does more than this, however: it also serves to develop, even unintentionally or unwittingly, standards. Consider one of Smith’s favorite examples, to which he recurs repeatedly in TMS, of joke-telling. To illustrate the power of the desire for mutual sympathy of sentiments, Smith asks us to imagine the following scenario (1.1.2.1). You are out with your friends one evening, and you decide you would like to tell your favorite joke. You do so, and, at its conclusion, you laugh heartily—only then to observe that no one else is laughing. How would you feel? Embarrassed, awkward, disappointed, perhaps some combination? One thing is certain: you would never do that again.

There are clearly rules about joke-telling. Some jokes are appropriate in some circumstances but not in others; some are generally appropriate, while some are never appropriate. Where do those rules of propriety come from? How do we learn them? And, of course, the rules change over time; how, and why, do they change?

Smith’s answer is that they change over time as people interact with one another, entrepreneurially trying out new things, receiving feedback in the form of sympathy or antipathy of sentiments, and then adjusting behavior in light of the pleasing or stinging feedback, as the case may be. As experiences like this are repeated hundreds and thousands of times—regarding not only joke-telling but all manner of judgments, behavior, and sentiments—we form habits, then regularities, and then, possibly, even principles of behavior based on them. We might even come to view some of them as not just pleasant (or unpleasant), but, if they are sufficiently reinforced by consistent feedback from others, as good (or bad). These can then become our moral sentiments.

One other crucial element of Smith’s account: human beings, he claims, are not born with moral sentiments. Instead, they develop them over time, as they interact with other human beings. He provides two arguments for this claim. First, infants and small children, according to Smith, have no moral sentiments whatsoever. They simply have wants, which they cry out to have satisfied. When they are old enough to interact with peers, however, they have their first experience of being judged: other children are not as indulgent as one’s parents might be. Being judged by one’s peers is an unpleasant and even shocking experience, but it serves to introduce us, as Smith puts it, to the “great school of self-command” (3.3.22). When we have the unpleasant experience of others disagreeing with our sentiments, we begin searching for ways to alter, and “command,” our behaviors and sentiments so that others are more likely to sympathize with them. Once we do so, a permanent desire to achieve such mutual sympathy is initiated in us.

Second, Smith offers a thought experiment. Imagine an adult who has grown up entirely isolated from other human beings—a solitary islander, a Robinson Crusoe from birth (3.1.3). Smith asks: could such a person exist and survive, would he have any distinctively moral sentiments? Smith’s answer: no. He might have likes or dislikes, and fears or attractions, but no sense of proper or improper. Such latter sentiments instead arise only with the experience of other human beings judging one another.

Smith’s account of the initiation and development of moral sentiments shares many similarities with economic markets. Both might more generally be described as systems of “spontaneous order” whose conventions and rules emerge from the behavior and interaction of human beings, rather than from an exogenous design (or designer). People try things out; some of their efforts fail, some succeed. Some habits of behavior are destructive, and are weeded out; others are constructive, and so get reinforced. Some of the latter might succeed not only in one place or time, or for one group or another, but for many places and times and for many, perhaps even all, groups. Such highly successful—and highly felicitous—discoveries might become so reinforced and so frequently recognized that they may become venerated, even considered the will of the gods or God. Perhaps they become considered part of a “natural law.”

There is much more in TMS to learn from and to appreciate beyond these provocative claims, but perhaps this has sufficed to whet the reader’s appetite. I have focused on Smith’s developmental account of moral sentiments arising from human interaction driven by the desire for mutual sympathy of sentiments. But there is much more complexity and sophistication to Smith’s full account. Indeed, I consider TMS to be the most important work in moral philosophy since Aristotle’s Nicomachean Ethics. No brief introduction can hope to capture it, but I hope that the occasion of the 300th anniversary of Smith’s birth, along with the many scholarly and popular remembrances of it, and TMS’s ready and accessible availability on the Liberty Fund site, will inaugurate a renewed interest in one of the deepest and most enduring works of moral philosophy of all time.

*This now standard scholarly notation refers, respectively, to the part, section, chapter (where applicable), and paragraph in TMS. Thus: “1.1.2.1” means part 1, section 1, chapter 2, paragraph 1. All further references to Smith’s text are to TMS.