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Thinking It Through: The Consequences of Polygamy

Defenders of traditional marriage argue that redefining marriage to include same-sex unions undermines marital permanency (lifelong union) and exclusivity (only one spouse). If biological sex doesn’t matter, they argue, then why should duration and number?

This is called a reductio ad absurdum argument. It attempts to show the absurd conclusions that legal recognition of same-sex marriage logically leads to—namely, the legal recognition of “temporary marriage” as well as multiple-partner marriage.

Not so absurd anymore

The problem is that our culture is becoming desensitized to the absurdity of these conclusions. For example, a 2009 Newsweek article stated that the United States already has more than 500,000 polyamorous households. The article concludes that perhaps the practice is more normal than we think, suggesting, “[I]t’s only a matter of time before the monogamous world sees there’s more than one way to live and love.”

In a 2013 Washington Post article, lawyer Paul Rampell introduced what he calls “wedleases”: marriage leases where two people commit themselves to each other for a period of years—one, five, ten, or whatever term suits the couple. At the end of the term the couple can choose to renew the marital lease or not. And according to a new USA Network survey, 43 percent of millennials ages eighteen to thirty-four prefer this kind of setup to traditional marriage.

Mounting a defense

Since we can no longer assume that the culture views the above unions as absurd, defenders of traditional marriage must mount a different defense of permanency and exclusivity. And the way to do this is the same way we defend sexual complementarity in marriage: we look to nature’s design for human sexuality.

In part one of my two-part article “Bringing Sanity to Sex,” I showed that nature ordains sex for procreation—that is to say, our sexed bodies are ordered toward the begetting of children. Part two lays out the rationale behind the unitive dimension of human sex—because we’re human, the procreative end necessarily involves an interpersonal union of knowledge and love.

This line of reasoning suffices to show that nature orders human sexuality to a heterosexual union, but falls short in rounding out the picture of traditional marriage—namely, that such a union is permanent and exclusive. This requires more unpacking.

Let’s take permanency first.

Till death do us part

Marital permanency flows from both the procreative and unitive ends of human sex. Consider the procreative, which necessarily involves not just creating but raising children. When nature has its way, childrearing can be required until eighteen to twenty years after the mother is no longer fertile due to age.

Childrearing even demands that the union be lifelong because the education parents provide their children doesn’t stop when their children move out on their own. Children need parents to provide help and counsel as they start their own families. Even in old age, parents educate their children by providing an example of how to stay faithful throughout marriage, how to handle retirement, and how to be good grandparents. As any parent with grown children living outside the home will say, “You never stop being a parent.”

Permanency also flows from the unitive dimension of sex. The sexual union of man and woman is an interpersonal communion of love. How could it be true love if it were conditional? Imagine a husband saying at the altar, “I’ll love you for only the period of time needed to rear our children. After that, I’m gone!” That’s absurd. Without the lifelong commitment, it wouldn’t be a true communion of love. Practically speaking, separation later in life could create hardships for survival, especially for the woman. Subjecting a spouse to such hardship is likewise contrary to marital love.

So, the procreative and unitive dimensions of human sex demand not only a heterosexual union but a lifelong heterosexual union.

What of exclusivity?

“A man shall leave his father and cleave to his wife

By exclusivity I mean a man cannot simultaneously have more than one wife (polygamy) or a wife more than one husband (polyandry). Let’s look at it from the side of the man first.

Although polygamy does not pervert the primary end of human sex—namely, procreation and the provision of the children’s basic needs, it does violate the unitive end and makes child rearing less perfect.

For example, in polygamous relationships there is no equality between husband and wife. Consider how the husband is in a position to demand all the service, attention, and love of his wife, but she must divide the service, attention, and love of her husband with many others. Such inequality makes her inferior to her husband. As the late Rev. Michael Cronin writes, “Before her children and the world she stands in the position little better than that of the slave” (Science of Ethics, vol. II, 421). It’s obvious this doesn’t jibe with the unitive dimension of heterosexual unions.

Motherly competition likewise brings disastrous effects upon the household. Each mother vies for the attention and affections of the common husband. The mothers also compete not to fall into inferior positions in the household. This competition is a recpe for jealousy, which then finds its way into every part of the family, rendering the happiness and contentment of the parents impossible.

Finally, no one in his right mind would say that it’s better for a child to grow up in a home where the condition of the mother is degraded, there is hatred among the mothers, and human affection is lacking for both the women and the children. Polygamy, therefore, is contrary to nature’s design for a lifelong heterosexual union. 

A man shall leave his father and cleave to his wife”

The above arguments against polygamy apply to polyandry as well. However, unlike polygamy, polyandry also contradicts the primary end of human sex: the procreation and basic rearing of children.

Consider procreation. In the case of polygamy, the greater number of women a man possesses, the greater number of children can be born. Therefore, polygamy harmonizes at least with nature’s purpose of sex in propagating the human race. Polyandry, on the other hand, can play no part in nature’s scheme to be fruitful and multiply because a woman cannot bear more children by having more husbands. Cronin puts it succinctly: “Nature has no use for such a union, and consequently it lies completely outside the natural order” (Science of Ethics, vol. II, 427).

We can also prove that polyandry is unreasonable in light of the father’s natural desire to know and have communion with his offspring. St. Thomas Aquinas puts the argument this way:  

[M]an naturally desires to know his offspring, and this knowledge would be completely destroyed if there were several males for one female. Therefore, that one female is for one male is a consequence of natural instinct” (Summa Contra Gentiles, III:124:1).

Therefore, polyandry cannot be a part of nature’s design for heterosexual unions.

Nature’s ordering to heterosexual marriage

Nature has ordained sex to be essentially procreative and unitive, and as such it orders human sex to heterosexual unions alone. But because these dimensions necessarily demand such a heterosexual union to be lifelong and exclusive, we can say that nature orders human sexuality to what has been traditionally called marriage—the lifelong union between one man and one woman ordered toward the generation and rearing of offspring.

With permanency and exclusivity grounded in nature’s blueprint for heterosexual unions, it becomes clear why the removal of biological sex in the redefinition of marriage necessarily makes the application of the “marriage” label arbitrary. If nature does not require sexual complementarity in marriage, then it has no bearing on the duration of marriage or the number of persons involved. Once “marriage” is divorced from nature, there is nothing in principle to stop those in power from defining marriage however they want. It’s a blank check for marriage. And that is truly absurd.

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