The Ethical Implications of Monogamy and Polyamory

Exploring the ethical implications of monogamy and polyamory – how should humans and society as a whole handle relationships?

    Divorce rates are increasing in the United States and other Western countries.[efn_note]National Center for Health Statistics.[/efn_note]

There may be many sociological, psychological and political reasons for this. And yet, despite this increasing divorce rate, cultural expectations in Western countries insist that monogamy ought to be the most desired form of sexual behavior, and the nuclear family ought to be the normal form of organization.

    This conventional wisdom is beginning to be challenged. For example, the organization Black Lives Matter claims in its foundational document: “We disrupt the Western-prescribed nuclear family structure requirement.”[efn_note]What We Believe. Black Lives Matter. [/efn_note]

This invites further thought as to whether there might be a mismatch between Western cultural expectations and our human nature. It is all too common for marriages to collapse after a few years, largely because of sexual boredom. Monogamy requires partners to remain loyal and engage in exclusive sexual activity. For some people, this may too much of a burden, as it may be in their nature to seek multiple sexual partners.

    Indeed, there is an increasing number of people who now engage in polyamory, the practice of sexual relationships with more than one partner. It is crucial to understand that polyamory is different from adultery. In adultery, one person deceives his/her partner, keeping the façade of monogamy. In polyamory, all parties consent.

    The presence of consent is a big factor in any moral defense of polyamory. If we accept John Stuart Mill’s “harm principle”, then any activity that involves consenting adults is morally acceptable. This is the foundation of any libertarian philosophy, and as such, polyamory is a perfectly moral practice. In polyamory, there is no harm, to the extent that all parties agree to it. Proponents of polyamory as a lifestyle insist on this particular point. For example, Dossie Easton and Janet W. Hardy argue in their seminal book The Ethical Slut: “First and foremost, ethical sluts value consent. When we use this word… we mean an active collaboration for the benefit, well-being, and pleasure of all persons concerned. If someone is being coerced, bullied, blackmailed, manipulated, lied to, or ignored, what is happening is not consensual. And sex that is not consensual is not ethical—period.”[efn_note]Dossie Easton & Janet Hardy. The Ethical Slut. New York: Greenery. 1997, p. 21.[/efn_note]

    However, not all ethicists are libertarians or strict adherents of Mill’s philosophy. Some ethicists might object that even if consensual, polyamory is immoral, to the extent that it is an unnatural practice. This argument has also been used against the morality of homosexuality (notably by philosopher Lord Patrick Devlin[efn_note]Patrick Devlin. Morals and the criminal law. Oxford: Oxford University Press, 1965.[/efn_note]). That particular argument against homosexuality is not much favored by ethicists or legislators today, but in the case of polyamory, there is an additional argument: children are involved, and they do not have the capacity to consent. Good nurture of children, so the argument goes, naturally requires a permanent bond between parents, and polyamory is a threat to that stability. Monogamy is the natural sexual disposition of human beings, and our behavior ought to reflect that.

    Ethicists who favor polyamory might reply by arguing that, in fact, monogamy (and by extension, the nuclear family) is not natural, but rather a cultural construction that has been especially (but arbitrarily) favored in Western countries. Polyamory is actually the natural way of doing things. 19th Century anthropologists provided some evidence for this claim. For example, Lewis Henry Morgan discovered that in some kinship systems, the term for “father” is the same for “uncle”, and the term for “mother” is the same  for “aunt”.[efn_note]Lewis Henry Morgan. Ancient society: Or, researches in the lines of human progress from savagery, through barbarism to civilization. Good Press, 2019.[/efn_note] Morgan believed this reflected an earlier time of “group marriage”, in which multiples adults were sexual partners, and the whole commune took care of the children, without any knowledge of paternity. Monogamy only arose with the development of private property (presumably as a result of the invention of agriculture); men would now have an interest to pass property to their offspring, but that could only be done if they had certainty of who their children were. Hence, patterns of sexual exclusivity were imposed, first on women, and then on men. 

    This theory was deemed too speculative, but it has had some recent defenders. In a recent provocative book, Sex at Dawn, Christopher Ryan and Cacilda Jetha provide some interesting data that would appear to support Morgan’s claim.[efn_note]Christopher Ryan & Cacilda Jethá. Sex at dawn: The prehistoric origins of modern sexuality. New York, NY: Harper, 2010.[/efn_note] Yet, the consensus amongst anthropologists and evolutionary psychologists remains that (serial) monogamy is largely natural. This is due to a simple yet very important reason: parental certainty. Raising offspring requires a huge parental effort, so evolutionarily, it only makes sense if men have some degree of certainty that the offspring that they are nurturing, actually carry their genes. For that very reason, jealousy is powerfully hardwired in human nature (more so in men than in women, as women can always be assured of who their offspring is), and consequently, jealousy makes polyamory unnatural.

    However, under one important philosophical argument, the discussion about whether monogamy or polyamory is natural, is moot. Many natural behaviors are unethical (rape, infanticide), and many unnatural behaviors are ethical or ethically neutral (curing cancer, using contraception). G.E. Moore famously warned ethicists to avoid the “naturalistic fallacy”, and it would appear that judging the morality of polyamory on the basis of what our Paleolithic ancestors were doing, is a case in point.

    Yet at the same time, we ought to be careful not to dismiss so easily the facts about human nature, when discussing the ethics (and more importantly, the legality) of particular sexual practices. Polyamory can indeed be an ethical practice amongst consenting adults, regardless of how unnatural it may be. But, can society at large be functional if children are not raised by parents who pair bond? Can polyamory be extended to group marriage with the sanction of the State? There have been plenty of historical cases (the Oneida commune, the hippie movement, etc.) in which these practices have been put in place, and ultimately, such societies either collapse, or naturally revert back to monogamous pair bonding after nefarious experiences or rampant jealousy.

    Perhaps moral philosophers might find a moral compromise, as follows. On an individual level, polyamory is morally acceptable. That would require big efforts on participants, as jealousy is always a powerful (yet manageable) psychological force. Yet at the same time, the State still ought to promote monogamy as the more desirable form of mating system. That needn’t imply the stigmatization of members of the polyamory community, but it would imply a public acknowledgement that monogamy provides many societal advantages.  


  1. National Center for Health Statistics.
  2. What We Believe. Black Lives Matter.
  3. Dossie Easton & Janet Hardy. The Ethical Slut. New York: Greenery. 1997, p. 21.
  4. Patrick Devlin. Morals and the criminal law. Oxford: Oxford University Press, 1965.
  5. Lewis Henry Morgan. Ancient society: Or, researches in the lines of human progress from savagery, through barbarism to civilization. Good Press, 2019.
  6. Christopher Ryan & Cacilda Jethá. Sex at dawn: The prehistoric origins of modern sexuality. New York, NY: Harper, 2010.

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Article Discussion

  • Posted by Andie

    17 October, 2020 at 10:59 pm

    "...jealousy is powerfully hardwired in human nature (more so in men than in women, as women can always be assured of who their offspring is), and consequently, jealousy makes polyamory unnatural" So in other words, non-monogamy is more of problem for men, because they have a need to know who their offspring are. If all who consider themselves feminists knew the history, scope and implications of the notion of monogamy being the ideal, anything else being immoral it's my belief no feminist would choose monogamy! The nuclear family does work- for men and men only. Studies show men married to a female live longer on average. Yet women face more violence from husbands than from men unknown to them. Men get possession of a womb essentially by being married and the benefit of children yet women alone carry the burden of birthing, and the majority of caring for that life. Women are punished more severely if "unfaithful" yet men are permitted to have physical intimacy with other women and face little to no consequence. It is one of the main reasons the sex trade industry has existed and continues to thrive throughout thousands of years. Monogamy is anti-feminist. But the author missed another point- often it is wrongly assumed that the motive for polyamory is sexual- this is a very patriarchal notion. People have more than one love when it comes to pets, kids, friends, yet lovers-because of the threat to male entitlement, having more than one lover is shamed and punished. When we become less patriarchal, we will be less monogamous. Love is not diminished when shared.

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