Adam Smith on Polygamy and Kin Networks

social order sociality social coordination social distance just sentiments polygamy kin networks

Patrick Fitzsimmons for AdamSmithWorks

What are the historical requirements for the emergence of stable liberal polities? Adam Smith suggests monogamous marriages as an important, steadying institution.

"Families meet not on violent terms, but on civil and economic ones instead. The polity can focus on improving the polity, rather than fighting."

December 28, 2022
Let us reflect with Adam Smith on the very broad historical requirements for the emergence of stable liberal polities. We are considering the sweep of centuries past and experiences ranging throughout Europe and beyond Europe.
Liberty requires institutions that keep potential oppressors from running rampant. If a despotic ruler is to be kept from subjugating the populace, opposition is required. Opposition may come in many forms, but Smith understood that multilateral opposition to a potential oppressor would provide more opportunities for countervailing forces. Conquerors from elsewhere are one form of oppressor, but the immediate challenge is facing down homegrown despots.
Meanwhile, a desideratum to avoiding great oppression is an institutional arrangement that spells political stability. Without political stability, the opportunities for potential oppressors are abundant, if constantly shifting. The struggle for power in an unstable polity (or wannabe polity) is almost inevitably oppressive. Political stability does not ensure the limitation of oppression, but it is necessary to a measure of liberty.
Borrowing the violence framework from Douglass North, John Wallis, and Barry Weingast (2009), we may say that in the absence of political stability rents are scooped up by those actors who have the most potential for violence. Actors would invest in violence potential. The product is a society in which actors are not thinking growth or more extensive cooperation, but rather rent-seeking and immediate personal security.
Adam Smith provided several examples of institutions that could conduce to a stable polity with multilateral opposition and resistance to despotism. One is monogamy—which is to say, laws and customs that prohibit polygamy. Monogamy as a social norm stands in opposition to polygamy.
The source is Smith’s Lectures on Jurisprudence (LJ); the index of the volume indicates 23 pages for polygamy: 150–9, 160–1, 166, 167, 171, 172, 173, 442–5, 448, 449. Polygamy features in both sets of lecture notes, which correspond to lectures given at Glasgow between late 1762 and early 1764. As for all of Smith’s other materials (including the Correspondence), although some contain pertinent material on kin networks, political development, and so on, “monogamy” and “polygamy” never appear in any of them.
In LJ, Smith shows a strong and unequivocal favor for monogamy, believing it to facilitate social and political stability. Indeed, Smith’s apparent opposition to legal polygamy, at least within certain historical settings, should be regarded as one his most significant exceptions to the liberty principle. Smith thought that sometimes direct liberty must be sacrificed for overall liberty.
For Smith, monogamy has three advantages over polygamy in fostering political stability:
First, monogamy leads people to socialize and expand their social networks outside the family. Families are tight kin-networks that may present advantages in the face of despotic or irregular power. But tighter kin-networks have also proven to have a negative correlation with democratic institutions (Schulz 2022). Monogamy helps to break down barriers to interaction between non-kin members.
Second, monogamy produces orderly, intergenerational succession in prominent families; prominent and powerful families enable peaceable succession; customs of peaceable succession lead to the emergence of a nobility. Monogamy also provides a focal point for who will be the next king, elevating one potential over another. When the next king is determined ex ante, violence is less likely to break out between potential claimants.
Third, monogamy creates focal points. For Smith, focal points were crucial in order for people to rise in force against a foreign or domestic oppressor. If the people have no focal individuals who stands above the rest, no leaders, they are unable to band together and form a significant counter to the oppressor and his affiliates. The advantages of monogamous succession and focal points relate to Smith’s ideas on the legitimacy of children.

Jealous wives and the jealous husband
“Polygamy excites the most violent jealousy, by which domestic peace is destroyed” (LJ 442). Smith focuses on two jealousy problems. The first is jealousy among wives for the attention of their husband. The second is among men. Smith saw both problems as inherent to polygamy. These jealousies destroy the domestic peace of the family and of the society.
The jealousy among the wives of a husband is multifaceted since polygamy presents both “a jealousy of love and a jealousy of interest, and consequently a want of tranquility” (LJ 443). The wives compete for their husband’s favor, attention, and resources as “the wives are all rivals and enemies” (LJ 442). Suppose that Jim is married to Maria, Sarah, and other women in a legally permitted polygamous marriage. Maria would like to monopolize or at least capture as much of Jim’s attention as possible. In Maria’s eyes, Sarah is a competitor for limited resource, and Smith’s lectures give the impression that the women will not share willingly. Maria and Sarah will “do all that they can to supplant their rivals” (LJ 151). There is now disorder in the household as there is unhealthy competition between the women.
The women feel jealousy also towards one another’s children. Both Maria and Sarah have children from Jim. Jim’s attention is also divided between the very numerous children. When she looks upon Jim’s attention, neither Maria nor Sarah will be happy. Maria’s affection is for her children, so she would prefer that Jim’s attention be more focused on her children. Maria now sees both Sarah and her children as competition and will act to further the interest of her own child. Jealousy between Maria and Sarah not only keeps them from cooperating, but easily turns invidious and mutually antagonistic. It is a source of trouble and anxiety for Jim. He receives no enjoyment from the exercise of his parental affections but is instead filled with vexation (LJ 153). Jim must deal with complaints from both Maria and Sarah as both “measure the affection of the father by her own, between which there is no proportion, as he is divided among 40 or 50 children and hers only among 4 or 5” (LJ 442-43). This is but one reason why men are not happy under polygamy.
Smith notes that women are competing with each other and missing out on potential social networks. But men, too, find disadvantages and social instability under polygamy.
David Hume and Smith pointed out that polygamy, compared to monogamous marriage, no more leaves the husband better off than it does the wives (LJ 153; see Hume Essays 184-85). There is the jealousy that Jim feels towards his neighbor Tom. Whereas in a monogamous country, each of the two men may not feel jealousy about his wife, nor suspect her of anything, it is different for polygamous societies. Jim, the polygamist, understands that Maria and Sarah have less reason to be faithful towards him. Maria and Sarah, living “where polygamy takes place…, being in absolute slavery” to Jim (LJ 445), have little interest in his affairs, similar to how a slave of labor has little concern for the affairs of his master. Jim knows that Maria and Sarah lack reason to be faithful to him, so there is a concern that the neighbor, Tom, may corrupt one of the wives. Jim feels jealousy towards Tom and “on account of the inequality betwixt” Jim and his wives “he can have no entertainment at his own house, no opportunity of social improvements” (LJ 443). Jim hides his wives away from Tom, “lest he bring a lover to his numerous wives” (Hume 1985, 185). Jim and Tom are unable to form a bond as their fear of the other corrupting their women is strong (LJ 153). Confident, cooperative relationships between men, between women, and between men and women are all difficult in polygamous societies.
Furthermore, jealousy caused by polygamy incentivizes violence between men. Modern research has shown that polygamy is correlated with higher levels of violent behavior among men (Henrich et al. 2012).
Smith saw that the jealousy of the wives causes disorder. The husband cannot quell the jealousy or rebellion of his wives himself. He resorts to eunuchs (LJ 152). A eunuch, no longer a viable competitor of the man, keeps the wives in line for his employer. In the absence of institutions that reward men for going the path of eunuch, it is a procedure forced on other men. The strongest man may subjugate his peers. Men then hide from each other.

Monogamy and Legitimate Succession
Smith saw monogamy as solving the problems of succession and legitimation, as “the effect of marriage is to legitimate the children” (LJ 447). The protection of liberty and curbing of elite power could not be done without handling the issue. Smith thought that “there should be some persons who are some way distinguished above the rest and who can make head against the oppressions of the king, or head the people when they are in danger of being oppressed by foreign invaders” (LJ 157). Monogamy allows one individual to be elevated above the others. In noble families, the elevated individual, after the father and husband, is the eldest son, destined to take over his father’s duties. The father can focus all of his accumulated knowledge and experience on his eldest son, facilitating intergenerational leadership learning.
The eldest prince takes over his father’s throne. In baronial families, before they were able to split up land and power among the children, the eldest son received the inheritance. Noble families begin to form around the elevated individuals.
Each noble family acts as a check on the others. The elevated individual acts as a focal point for soldiers to rally around. As long as a focal point is present, noble families pose a counterweight to one another.
Clear succession is difficult if the elevated child is seen as illegitimate. In monogamous marriages, a child is seen as legitimate, so men are incentivized to enter monogamous marriages. Monogamous marriage handles paternal uncertainty and resolves doubts about the man’s rightful heirs (Henrich 2016, 146). In polygamous societies, the connection between child and father is scarce and will have no effect (LJ 157) and the there is no definitive son to be followed.
The only type of family that solves the problem is the family of hereditary nobility, specifically a monogamous family of hereditary nobility. If there is no clear monogamous hereditary nobility, half-brothers become rivals. In a polygamous society, the lack of hereditary nobility coupled with a severe distrust between men leads to tyrannical oppression, as the men are “by this means altogether incapacitated to enter into any associations or alliances to revenge themselves on their oppressors, and curb the extravagant power of the government and support their liberties” (LJ 154.33).

The liberty issue
Smith, citing Grotius, said that there is no injustice in polygamy in countries where it is allowed (LJ 150). Thus, we come to the issue of whether prohibiting polygamy violates commutative justice and thus reduces liberty. That issue for polygamy relates to several other kin issues, including whether restrictions on incest, marrying among kin, “voluntary divorce,” and neglecting one’s own children violate commutative justice and hence reduce liberty.
For Smith, when polygamy is allowed and a wife is taken as one of many wives, there is no injury to her when she finds herself in that situation. But while “there is not any injustice in the practise of polygamy where the law permits it, yet it is productive of many bad consequences” (151).
Smith is referring to countries where polygamy is allowed by law. The woman needs to be aware that she is going to be one of many wives. The man must be honest about the terms the woman is agreeing to.
It is my opinion—without getting into the parsing of the matter—that Smith would have supported restrictions on polygamy as an exception to the liberty principle in the direct sense, since Jim, Mary, and Sarah violate no one’s person, property, or promises-due when they voluntarily agree to bigamy, and to bring violence against such a voluntary affair is to initiate coercion and violate liberty.
But when it comes to liberty in an indirect or overall way, or ramifications, Smith lays out how monogamy instead of polygamy provides safeguards to a nation’s liberty. Smith clearly sees a connection between liberty and monogamy—“polygamy takes place under despotic governments” (LJ 443). Monogamy not only leads to liberty, but liberty may lead to monogamy as “in every country freedom puts out polygamy” (LJ 443).

Concluding remarks
Smith on monogamy versus polygamy relates to the wide considerations of what made possible a modern era of relatively liberal nation-states. The topic treated here relates to restrictions on incest, consanguineous marriages, and divorce, as such regulations, too, would be regarded by Smith as exceptions to the direct-liberty principle, but favorable to liberty overall. He treats those topics in LJ, but not as extensively as polygamy (on consanguineous marriage and incest, see especially 163–68, 441, 446–48).
In The Theory of Moral Sentiments, in speaking of sympathy and concern among family members, Smith gives two paragraphs to a contrast between “pastoral countries” and “commercial countries,” relating familial sentiments to “the authority of law” and, implicitly, to kin structure. “In commercial countries, where the authority of law is always perfectly sufficient to protect the meanest man in the state, the descendants of the same family, having no such motive for keeping together, naturally separate and disperse, as interest or inclination may direct” (TMS 223.13).
Smith makes a similar connection between commerce, kin-networks, and development in Wealth of Nations, Book III: Of the different Progress of Opulence in different Nations. Chapter IV is about how the towns contribute to the improvement to the countryside. As the commercial towns grow in size and power, and the country begins to improve, the kin-networks of the barons are slowly eroded. The kin-networks based on blood, marriage, and honor are replaced with social networks based on commercial ties. Barons become gentlemen. Without the kin-networks, and with gentlemen able to split inheritance among their children, the successive wealth of each generation decreases. Smith notes that “in commercial countries, therefore, riches, in spite of the most violent regulations of law to prevent their dissipation, very seldom remain long in the same family” (WN 422). Families meet not on violent terms, but on civil and economic ones instead. The polity can focus on improving the polity, rather than fighting.

Patrick Fitzsimmons is a PhD student in economics at George Mason University, focusing on economic history. He is interested in early historical development and in the effects of informal and formal institutions on long-term development.

This essay is part of the AdamSmithWorks series Just Sentiments curated by Daniel B. Klein and Erik Matson. New essays will be published on the fourth Wednesday of the month. You can read more about the series in this Speaking of Smith post, "Just Sentiments- Welcome!". Klein and Matson lead the Adam Smith Program in the Department of Economics at George Mason University, in association with the Mercatus Center. In the program, they study big ideas in jurisprudence, politics, ethics, and economics as they were pursued during the original arc of liberalism, especially in the 18th century in Britain.

Henrich, Joseph, Boyd Robert and Richerson Peter J. 2012. The Puzzle of Monogamous Marriage. Philosophical Transactions of the Royal Society 367 (1589): 657–669.
Henrich, Joseph. 2016. The Secret of Our Success: How Culture Is Driving Human Evolution, Domesticating Our Species, and Making Us Smarter. Princeton; Oxford: Princeton University Press.
Hume, David. 1985. Essays: Moral, Political and Literary. Edited by Eugene F. Miller, Liberty Fund.
North, D.C., Wallis, J.J. and Weingast, B.R. 2009. Violence and social orders: A conceptual framework for interpreting recorded human history. Cambridge University Press.
Schulz, Jonathan F. 2022. Kin Networks and Institutional Development. The Economic Journal 132 (647): 2578-2613.
Smith, Adam. 1976a. An Inquiry Into the Nature and Causes of the Wealth of Nations. Edited by W.B. Todd et al., Oxford University Press; Liberty Fund, 1982.
Smith, Adam. 1976b. The Theory of Moral Sentiments. Edited by D.D. Raphael and A.L Macfie. Oxford University Press; Liberty Fund 1982.
Smith, Adam. Lectures on Jurisprudence. 1978. Edited by R.L. Meek, D.D. Raphael, and P.G. Stein. Oxford University Press; Liberty Fund, 1982.