The Principle
The Western legal tradition's insistence on monogamy - one spouse at a time, under criminal penalty for violation - is one of the most direct translations of biblical theology into enforceable law. While polygamy was practiced by many Old Testament figures and regulated rather than prohibited in Mosaic law, the early church reading of Genesis 2:24 and Jesus's teaching in Matthew 19:3-9 produced a monogamy norm that canon law codified and Western states subsequently criminalized.
Biblical Foundation
Genesis 2:24 provides the normative foundation: 'That is why a man leaves his father and mother and is united to his wife, and they become one flesh.' The singular 'wife' and the language of unity - one flesh - became the canonical argument for monogamy. Jesus cites this text in Matthew 19:4-5 and adds: 'So they are no longer two, but one flesh. Therefore what God has joined together, let no one separate.' This appeal to the creation order as the standard for marriage - predating Mosaic concessions to human hardness of heart - provided Christian theologians the foundation for treating monogamy as the permanent divine intention.
1 Timothy 3:2 requires that a bishop be 'faithful to his wife' (literally, 'a one-woman man'). While this requirement was specifically for church officers, canonists extended its principle to all Christians - arguing that if even the most permissive interpretation allowed plural marriage for ordinary believers, the church's leadership requirement of exclusivity implied a universal monogamy norm.
Historical Transmission
The early church, operating in a Greco-Roman culture that technically practiced monogamy but tolerated concubinage, focused primarily on fidelity and the permanence of marriage. Augustine's On the Good of Marriage (c. 401) argued that monogamy is the divinely-intended form of marriage and that Old Testament polygamy was permitted by God as a concession to the need for population growth in ancient Israel - a providential accommodation that the coming of Christ superseded.
The Fourth Lateran Council (1215) codified marriage law comprehensively, requiring public announcement of marriages to prevent clandestine bigamy and establishing ecclesiastical courts as the forum for all marriage disputes. Bigamy - entering a second marriage while the first spouse lived - was prosecuted as a canonical offense.
In England, the Bigamy Act of 1603 made bigamy a capital felony under secular law - not just a canonical offense - reflecting the Protestant states' assumption of marriage jurisdiction from the church after the Reformation. The death penalty was rarely applied but the criminalization was absolute.
Key Champions
Reformation marriage theology, particularly Calvin's Geneva consistory, enforced monogamy vigorously through church discipline that fed into civil courts. The Mormon practice of plural marriage in 19th-century America generated the most significant legal test of the monogamy principle in American history. Reynolds v. United States (1879) upheld federal anti-polygamy legislation against a First Amendment free exercise challenge, with the Supreme Court treating monogamy as the foundation of Western civilization itself and citing the Old Testament polygamy as a warning about barbarism.
Modern Application
Bigamy remains a criminal offense in virtually all Western jurisdictions. In the United States, all 50 states criminalize bigamy, typically as a felony. The arguments for criminalization are now largely secular - protecting spouses from fraud, ensuring the integrity of the marriage registration system - but the underlying norm of monogamy traces directly to Genesis 2:24 and its Christian interpretation.
The emergence of polyamory as a lifestyle and the increasing public discussion of relationship plurality have generated academic legal literature arguing that bigamy laws are unnecessary and disproportionate where all parties are consenting adults. Several US jurisdictions have decriminalized consensual adult plural relationships while maintaining fraud provisions. Utah partially decriminalized polygamy in 2020, though legal plural marriage remains prohibited.
Scholarly Debate
Biblical scholars note the tension between the creation order monogamy of Genesis 2 and the polygamy of Abraham, Jacob, David, and Solomon. Some argue, with Augustine, that Old Testament polygamy was a providential concession; others argue that the Genesis 1-2 creation narrative establishes a permanent norm that the rest of the Old Testament fell short of but was never intended to supersede. The debate has implications for Christian engagement with polygamous cultures in Africa and Asia, where missionaries have historically required converts to divorce all but one wife - a requirement that leaves abandoned wives and children in severe economic hardship and has been increasingly questioned by African theologians as a failure of contextual application.
Comparative Perspective
The biblical-Christian insistence on monogamy as the only legitimate form of marriage for all persons, regardless of status, is historically distinctive. Most societies have permitted polygamy for elite males, though demographic realities made monogamy the statistical norm for most individuals. Islam's permission of up to four wives represents the most significant alternative in Abrahamic law. The debate about whether monogamy reflects universal natural law or merely a Christian cultural convention has direct implications for bigamy law in pluralistic societies. The African Christian theology debate about requiring converts to divorce all but one wife illustrates the practical difficulty of applying the monogamy norm across cultural contexts with different social structures: wives who are divorced face severe economic hardship, raising the question whether the canonical rule serves the women it purports to protect. The criminalization of bigamy in Western law reflects centuries of canon law and common law development grounded in the Matthean and Pauline texts that defined Christian marriage as exclusively dyadic. As Western legal systems become more pluralistic, the tension between this inherited norm and the marriage practices of immigrants from polygamous cultures will require legal systems to reason more carefully about the theological and natural law foundations of the monogamy rule, and about whether criminal prohibition is the appropriate tool for enforcing a marriage norm whose rationale is partly theological. The biblical trajectory from patriarchal polygamy to prophetic monogamy to New Testament exclusive pair-bonding reflects a developing understanding of marriage as a covenant of total mutual commitment that criminal bigamy law now institutionalizes. The contemporary legal challenge for bigamy law in pluralistic Western societies is to articulate the monogamy norm in terms that do not depend exclusively on theological premises, while acknowledging that the theological premises shaped the law and continue to motivate adherents. The natural law tradition offers a partial secular rationale -- that the dyadic structure of marriage reflects the complementarity of persons in a way that polygamous structures do not -- but this argument remains contested. Meanwhile, the practical harms of unauthorized polygamy, including the non-legally-recognized co-wives who lack inheritance and spousal benefit protections, provide a feminist rationale for bigamy prohibition that converges with the canonical one. The biblical tradition itself, moving from patriarchal polygamy through prophetic critique to New Testament monogamy theology, demonstrates that marriage norms are not static but develop toward a more complete expression of covenant faithfulness.