In The Western Case for Monogamy Over Polygamy, John Witte Jr. explores the various legal and social rationales given for defining marriage as a union of one man and one woman rather than as a union of more than two persons. He deftly explores centuries of legal, theological, and social arguments in favor of monogamy, as well as the arguments repeatedly raised and rejected in favor of polygamy.

Witte begins his historical account with the ancient Hebrews, who permitted polygamy by appeal to the example of Biblical patriarchs such as Abraham, Jacob, and Solomon—heroic figures who had multiple wives at the same time. If polygamy is so wrong, how can we account for the fact that the legendarily wise “King Solomon had a harem of 700 wives and 300 concubines”? The Biblical precedent set by the patriarchs served as a justification for polygamy for generations of later writers, and became a puzzle requiring explanation for those who condemn polygamy.

The polygamy of the patriarchs, however, may not be an example to imitate but a warning of what to avoid. The Biblical stories exemplify the problems generated by plural marriage: rivalry among co-wives, hatred among half-siblings, disputes over inheritance, and even war. As Witte notes, “The Hebrew word for a co-wife (tzarah) literally means ‘trouble’.” He continues, “royal Greek polygamists had the same bitter experiences with polygamy that befell the Old Testament polygamists.” Wives hated each other and sought preeminence for themselves and their own children, half-sibling rivals hated each other, and stepmothers and stepchildren hated each other most intensely of all. Painful experience brought Athens and Jerusalem to the same conclusion.

Later in history, the teachings of Jesus—with his emphasis on the Genesis account of marriage as between one man and one woman—gave a theological foundation for monogamy. Witte notes, “Roman law maintained a sexual double standard, forbidding wives to commit adultery but allowing husbands to indulge with impunity in sex with prostitutes and slaves. Christianity denounced extramarital sex altogether, and called Christian husbands and wives alike to remain faithful to each other exclusively.”

Christian writers sought various explanations for the polygamy found in the Hebrew Scriptures. Tertullian accounted for polygamy as a temporary dispensation, granted so that human beings might fill up the world as rapidly as possible. Because one man can impregnate numerous women, but a woman can only get pregnant by one man at a time, women are the limiting factor in reproduction. Women in polygamous societies marry at a younger age than women in monogamous societies, so they are able, on average, to have more children over the course of their lives. Considered in terms of numbers alone, polygamy is a more efficient means of human reproduction than monogamy.

St. John Chrysostom accounted for polygamy as suitable for ancient, primitive societies but unsuitable for modern, more developed societies. As a rule, polygamy imperils the education of women (who marry much younger) and of their children (who have younger mothers). Inasmuch as education is more important in modern societies than in ancient undeveloped societies, monogamy is more suitable for modern societies.

With the writings of these patristic authors and the Christianization of western culture, the Church’s teachings on monogamy and condemnation of polygamy were “slowly adopted and enforced” in the West. The same rules of conduct in marriage applied to rich and poor, to king and peasant alike. Equality before the marriage law became the norm.

In the Middle Ages, these norms were for the most part reinforced through scholastic writing. William of Auvergne (d. 1249) argued that natural equity required monogamy so that every man and every woman have potential marriage partners available. If one man takes numerous women as wives, some men who would like to marry will be without wives altogether. This results in increased violence, fraud, prostitution, adultery, rape, and abduction, much to the harm of society.

Witte devotes ample attention to the teaching of St. Thomas Aquinas that polygamy violates the good of marriage by making marriage a kind of slavery of the man over his wives, rather than an association of equals and the greatest kind of friendship. On the other hand, Blessed John Duns Scotus thought that God could grant a dispensation for polygamy through the Church, and other theologians such as Cardinal Cajetan and St. Robert Bellarmine followed Scotus in allowing exceptions.

Official church teaching endorsed the stricter view. Pope Innocent III reasoned that if the Gospel does not permit marriage to another when a spouse is sent away in divorce, how much less would marriage to another be permitted if the spouse is retained? The Council of Trent taught, “if anyone says it is lawful for Christians to have several wives at the same time and that it is not forbidden by any divine law (Matt 19:4ff.), let him be anathema.”

Protestants also largely condemned polygamy, with a few notable exceptions. Henry VIII considered polygamy a way to solve his desire for an heir, and Martin Luther granted a “private dispensation to practice polygamy” to Prince Philip. In the 1530s in Munster, Germany, the Anabaptists practiced polygamy on a widespread scale—with bloody results. As Witte notes, “This Munster experiment proved a textbook example of the many harms that polygamy had already occasioned in biblical times: rape, coerced marriage, household rivalry, abused wives and children, lustful patriarchal excess, battery and murder, social destruction, and warfare.”

Following the Munster experience, all Christians strongly condemned polygamy. Secular law also punished the crime in various and severe ways, including loss of voting rights, whipping, fines, perpetual banishment, hard labor, castration, decapitation, and stoning. Witte describes the seventeenth-century English mind on polygamy: “Too often in polygamous households, wives were commodified, exploited, and abused; children were neglected, undereducated, and made rivals; men were too tempted by their lawful lustful pursuits of other wives to attend to their domestic duties or provide their children with healthy models for the good moral life.” Not religious courts but secular authorities moved decisively and harshly against polygamy. Witte points out that “In 1604, the English parliament for the first time in its history made polygamy a secular crime in England—and a capital crime at that.”

Enlightenment thinkers provided non-theological arguments. For example, Henry Home (1696–1782) of Scotland’s high court justified monogamy as an expression of equality, “All men are by nature equal in rank; no man is privileged above another to have a wife; and therefore polygamy is contradictory” to the natural right of each person to marry. “Men and women are by nature equal, Home argues at length,” Witte points out. “Monogamous marriage is naturally designed to respect this natural gender equality.” But an equality of a different sort can also be established through allowing each person to have as many spouses as agree to marriage. Although rejecting revealed theology, David Hume argued against polygamy as fostering jealousy and competition among wives, as well as leaving many children without proper paternal investment. The relationship between husband and wife is poisoned as the husband seeks new wives and each wife comes to be viewed as a replaceable commodity rather than an irreplaceable lover and friend.

Non-theological arguments were given in favor of polygamy too. In cases in which the population needs to grow rapidly, polygamy facilitates population growth more effectively than monogamy. As Witte notes, “the obvious raw advantage of polygamy for repopulating early modern lands devastated by war and disease or for providing more homes for fatherless children and single women kept alive the ‘necessity’ and ‘utility’ arguments for polygamy.” The interest of powerful men to have heirs or simply more authorized sexual partners drives motivation for polygamy. Witte notes, “the Western case for polygamy is and always has been primarily about a small group of men seeking the social, moral, and legal imprimatur to have and to hold sundry females at once.” A woman’s interest in polygamy is found in cases of massive male deaths in war, which can leave many women without husbands.

The arguments for polygamy did not carry the day, before or after the Enlightenment. As Witte notes:

In an important sense, making the non-religious case against polygamy was nothing new for the Western tradition. Already the ancient Greeks and Romans, long before the birth of Christianity, had prohibited polygamy for reasons of nature, friendship, domestic efficiency, political expediency, and more. These non-religious arguments always remained at the foundation of the ongoing Western case against polygamy.

The brutal punishments for polygamy included being “branded on the forehead with an ‘A’ for adultery,” branded on the cheek with a ‘B’ for bigamist, or “bored through the tongue with a red hot iron” as an expression of the false vow made with the tongue.

Witte’s book includes a fascinating discussion of early (1840s) Mormon teaching on polygamy, which was later abandoned in 1890. An 1882 law disqualified polygamists from voting rights, sitting on juries, and holding public office. The US Supreme Court turned aside the claims of free exercise of religion lodged by polygamists in Reynolds v. United States (1879), Davis v. Beason (1890), and Church of Jesus Christ of Latter Day Saints v. United States (1890). In Murphy v. Ramsey (1885), the Supreme Court declared:

Certainly no legislation can be supposed more wholesome and necessary in the founding of a free, self-governing commonwealth, fit to take rank as one of the coordinate States of the Union, than that which seeks to establish it on the basis of the idea of the family, as consisting in and springing from the union for life of one man and one woman in the holy estate of matrimony; the sure foundation of all that is stable and noble in our civilization; the best guaranty of that reverent morality which is the source of all beneficent progress in social and political improvement.

Contemporary sociological research provides extensive empirical evidence justifying the claim that polygamy is disadvantageous for society. Witte cites Rose McDermott’s cross-cultural study of polygamy in 170 countries, which showed,

increased levels of physical and sexual abuse against women, increased rates of maternal mortality, shortened female life expectancy, lower levels of education for girls and boys, lower levels of equality for women, higher levels of discrimination against women, increased rates of female genital mutilation, increased rates of trafficking in women and decreased levels of civil and political liberties for all citizens.

At times, the case against polygamy has been made using arguments, often theological, that would not now hold much sway in the contemporary public square. The case against polygamy begins by considering marriage as a public good. The status of being married is not just about the individual persons and their private relationships; the state publicly recognizes marriage because marriage is a central component of the political common good. Legally recognizing polygamy is a matter entirely different from criminalizing three or more people who live together in a sexual relationship. To recognize polygamy in law is to ask for a governmental stamp of approval of such relationships as “marriages.” We may ask, therefore, whether polygamy is to the advantage or disadvantage of the public good.

Witte’s book is not a systematic political or philosophical treatise against polygamy. It rather provides a useful survey of what has been said over more than 2,000 years of discussion of the issue. The truth is that the good of marriage, and through it the good of future generations, is at stake in how we understand marriage and legally define it.