Smith explains Hume’s theory of the social evolution of our ideas about justice.

George H. Smith was formerly Senior Research Fellow for the Institute for Humane Studies, a lecturer on American History for Cato Summer Seminars, and Executive Editor of Knowledge Products. Smith’s fourth and most recent book, The System of Liberty, was published by Cambridge University Press in 2013.

Why is society advantageous to man? Because, said David Hume, we require for our survival and well‐​being many things that we cannot easily (if at all) provide for ourselves but which require the cooperation of others. Three factors are primarily responsible for the benefits of social cooperation. First, the division of labor increases the productive capacity of society beyond that which could be achieved separately by its members. Second, specialization enables us to improve our skills beyond what would be possible in a solitary state. Third, society provides a remedy in times of emergency, as when illness or a natural disaster leaves us destitute. In society, such emergencies will bring friends and family to our aid, whereas they would probably cause our death in a solitary condition.

Society therefore helps us in three basic ways: First, it combines and coordinates the labor of many people and thereby increases our own economic power. Second, it enhances our personal abilities by permitting us to concentrate on a specialized area. Third, it vastly improves our security by providing various sources of support and assistance during emergencies. “’Tis by this additional force, ability, and security that society becomes advantageous.”

The mere existence of these benefits is not enough, however—people must become aware of why they are advantageous if those benefits are to be sustained in the long run. And this knowledge could not have been attained through reason alone. Why? Because the beneficial consequences of social cooperation are “remote and obscure” rather than immediately obvious. So how was this knowledge first acquired? Here Hume pointed to “that natural appetite betwixt the sexes” as the preeminent cause of the habit of social cooperation. Our natural sexual impulses, by producing children, create the miniature society of family members. The parents are stronger than their offspring, and so are able to enforce their wills; but they also have a natural affection for their children, which causes them to moderate their power. Meanwhile, as children grow up in their familial society, they come to understand and appreciate the benefits of social cooperation. They acquire the social habits, skills, and temperament that will render them fit to cooperate with strangers and others beyond their immediate family.

The crucial difference between a family and a larger society is that in the latter we must interact with strangers, people for whom we feel no natural affection. Hence our natural benevolence toward family and friends cannot account for the sentiment of justice, which requires impartiality above all else. Justice does not allow favoritism; it does not permit us to treat people we like differently from people we dislike. This is why our natural feelings of benevolence cannot account for the impartial sentiment of justice: benevolence is always partial, causing us to favor some people over others. How, then, can we explain the social evolution of justice? How can we account for this disinterested sentiment, given that man’s natural social sentiments are biased in favor of himself and his inner circle of family and friends?

It was while addressing this question that Hume mentioned three kinds of goods that are possessed by human beings: the internal satisfaction of our minds, such as happiness; the external advantages of our body, such as health; and the material possessions we have acquired through industry and good fortune.

The first category of goods, those pertaining to internal satisfaction, cannot be taken from us. The second, our physical capabilities and condition, can indeed be damaged or destroyed by another person, but the aggressor can gain nothing for himself by doing so. But the case is different with the third species of goods, our material possessions.

[Our possessions] alone are both exposed to the violence of others, and may be transferred without suffering any loss or alteration; while at the same time, there is not a sufficient quantity of them to supply every one’s desires and necessities. As the improvement, therefore, of these goods is the chief advantage of society, so the instability of their possession, along with their scarcity, is the chief impediment.

Property would be insecure in a state of nature, and it is in vain, said Hume, to expect a remedy for this inconvenience from man’s uncultivated nature, which is dominated by his natural passions. As noted previously, people will naturally value their own welfare and the welfare of their inner circle (family and friends) over other members of society, so our natural affections are inconsistent with the sentiment of justice. Rather than cultivate a concern for strangers, our partial passion of self‐​interest will tend to strengthen the value we place on ourselves and our inner circle at the expense of everyone else.

This is what Hume meant when he said that justice is not a natural virtue. We are not naturally inclined to value everyone equally, without showing favoritism to self, family, and friends—but this is exactly what the virtue of justice requires. What nature fails to provide, however, is compensated for by our judgment and understanding. As we become aware of the advantages of social cooperation, we also become aware of the need for security in our external possessions.

This can be done after no other manner, than by a convention entered into by all the members of society to bestow stability on the possession of those external goods, and leave every one in the peaceable enjoyment of what he may acquire by his fortune and industry. By this means, every one knows what he may safely possess; and the passions are restrained in their partial and contradictory motions. Nor is such a restraint contrary to these passions; for if so, it could never be entered into, nor maintained; but it is only contrary to their heedless and impetuous movement. Instead of departing from our own interest, or from that of our nearest friends, by abstaining from the possessions of others, we cannot better consult both these interests, than by such a convention; because it is by that means we maintain society, which is so necessary to their well‐​being and subsistence, as well as to our own.

Hume stressed that the “convention” of respecting property rights does not arise from a contract among members of society. Rather, it arises from a sense of common interest that induces people to regulate their conduct by certain rules. I observe that it is in my interest to respect the property rights of another person, provided he respects mine. And he is also aware of the advantage to be gained from this reciprocity. Therefore, as we each become aware of the advantages of reciprocity, we adjust our behavior accordingly, without ever consulting each other or making an explicit pact wherein we exchange promises.

There is, Hume conceded, a kind of agreement involved in this social convention, but it does not involve mutual promises. My actions are taken with a view to your actions and are predicated on the expectation that you will behave in a certain way. But I never promise you that I will act in a certain manner, nor do you promise me. Hume compared this situation to two men rowing a boat. Each man exerts labor on the supposition that the other man will do likewise, and each adjusts his movements to the movements of the other—but all of this occurs without an exchange of promises or an explicit agreement between the two men. The cooperation is spontaneous and implicitly understood, not planned in advance and expressed in promises or a contract.

Property rights, therefore, arise over time, as people become sensible of the need for security, and as they become aware that this security can best be achieved by respecting the property rights of everyone in society. And this occurs without any exchange of promises. The institution of property is largely a spontaneous product of self‐​interested behavior. No ancient lawgiver, such as Moses or Lycurgus or Solon, figured out the advantages of private property and bestowed the necessary laws for protecting them on the rest of humanity. Property rights—like language and money—evolved over time and were established as conventions, as people came to respect them routinely, as a matter of habit.

Hume’s account is especially significant for classical liberal ideology because of its stress on the fusion of self‐​interest and public utility through property rights, which is the institutional manifestation of justice. As with many British moralists, Hume treated self‐​interest as a natural sentiment, an inherent disposition in human nature, that can lead to either good or bad consequences, depending on how it is managed and directed by reason.

Justice forbids us to interfere with the property rights of others, and when such rights are secure, “there remains little or nothing to be done towards settling a perfect harmony and concord” in society. Social harmony cannot be achieved, however, so long as man’s natural passions, which give “preference to ourselves and friends, above strangers,” are “not restrained by any convention or agreement.” Our partial self‐​interest, if unrestrained by reason, generates the anti‐​social passion of avidity—the desire to acquire goods and possessions for ourselves and our nearest friends. Avidity is “insatiable, perpetual, universal, and directly destructive of society,” so this passion must be regulated or checked. But benevolence toward strangers is too weak to “counter‐​balance the love of gain,” as are other passions not linked to self‐​interest. This leaves only self‐​interest itself, rightly understood, to counteract the undesirable consequences of a partial self‐​interest, narrowly conceived. We moderate our self‐​interested passions as we come to understand the long‐​range benefits of social cooperation.

There is no passion, therefore, capable of controlling the interested affection, but the very affection itself, by an alteration of its direction. Now this alteration must necessarily take place upon the least reflection; since ’tis evident, that the passion is much better satisfy’d by its restraint, than by its liberty, and that by preserving society, we make much greater advances in the acquiring possessions, than by running into the solitary and forlorn conditions, which must follow upon violence and an universal licence.

That self‐​interest must restrain and regulate itself leads to an interesting observation about its moral status. Whether self‐​interest be deemed virtuous or vicious has no bearing whatever on the origin of society, according to Hume. Whether we view man’s social nature as arising from his virtues or vices does not alter the fact that the self‐​interested passions are too strong to be checked by anything other than themselves. The key issue, therefore, does not concern the goodness or wickedness of human nature, “but the degrees of men’s sagacity or folly.”

The self‐​interested passion of avidity restrains itself by the establishment of property rights—a “rule for the stability of possessions.” Nothing is more “simple and obvious” than the need for this rule. Every parent understands its role in maintaining peace among his children, and it will quickly improve as the society becomes larger. Hume therefore dismissed the possibility that men could long remain in “that savage condition, which precedes society.” On the contrary, “his very first state and situation may justly be esteem’d social.” The supposed pre‐​social state of nature—that Hobbesian condition of perpetual strife—is a philosophical fiction, an abstraction that never did, nor ever could, exist in reality. It is a hypothetical model concocted by philosophers in which the two principal parts of human nature—the affections and the understandingare mentally separated, and the former considered in isolation from the latter. To imagine human beings as being driven solely by their passions without any direction from the understanding is necessarily to incapacitate them for social life.

In short, according to Hume, the rules of justice are artificial, in the sense that they do not spring naturally from innate sentiments and dispositions. Instead the rules of justice emerge as we reason about the lessons of experience, which teach us that justice is an indispensable condition for social order and harmony. Justice cannot be deduced from the nature of rational beings alone, as moral rationalists maintained. We must also take into account the nonrational features of human nature, such as our natural sentiments, and the external conditions in which people find themselves, such as the requirements imposed by economic scarcity.

In this essay I have sought to explain, not to criticize, some of Hume’s ideas about justice, social order, and self‐​interest. I shall take on the critical task in a subsequent essay.