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National Marriage Week: What does sexual difference have to do with marriage?

Today is the fourth day of National Marriage Week. On Tuesday, we reflected on what makes marriage unique, different from any other relationship on earth. Today the topic is more focused: why does sexual difference matter for marriage? In other words, why is marriage the union of one man and one woman?

What is sexual difference?

1)      The call to accept one’s sexual identity as a man or as a woman

As we did before, let’s begin with the human person, with an authentic anthropology. Crucial here is the fact that to exist as a human person means to be embodied. (When was the last time you met someone without a body?) Echoing Bl. John Paul II’s terminology, we can say that the body “reveals” man and is “an expression of the person” (TOB, 9.4 and 27.3). In other words, encountering a living human body means at the same time encountering a human person. The body is not just a shell or a conduit for one’s “real” self but is intimately and inseparably united with one’s identity, one’s “I”.

Further, to exist as a human person means to exist as a man or as a woman. The human body is fundamentally a gendered reality, not a gender-less (androgynous) one.[1] And because the body is a deeply personal reality and not just a biological fact, being a man or being a woman is not just a matter of anatomical features or “the shape of my skin.” Instead, one’s sexual identity – as a man or as a woman – affects a person at every level of his or her existence (biologically, psychologically, genetically, and so forth). As the Catechism puts it, “Sexuality affects all aspects of the human person in the unity of his body and soul… Everyone, man and woman, should acknowledge and accept his sexual identity” (CCC, nos. 2332 and 2333, emphasis in original).

2)      An irreducible and dynamic difference

What does sexual identity have to do with sexual difference? Simply this: when we speak of sexual difference, we mean both the existence of two distinct sexual identities (man or woman) and the built-in mutual relationship between them. In other words, sexual difference has to do with the irreducible and dynamic difference of man to woman and woman to man.

Why “irreducible”? Because sexual difference is primordial, basic, and unique. It is fundamental to human experience and reality. Unlike other differences between people, sexual difference undergirds everything that we are as human persons, male or female. Sexual difference cuts across geographic, ethnic, and other differences, being in fact more basic than these other differences.

Why “dynamic”? Because sexual difference distinguishes in order to unite. In fact, sexual difference is precisely what enables communion between man and woman to exist at all. (More on this soon.)

Put another way, sexual difference is a mutually referential kind of difference – we know woman fully only by knowing man, and know man fully only by knowing woman. The differences between them do not just set them apart but hint at something more, at a call to communion between them. This call to communion inscribed in man and woman is part of what Bl. John Paul II had in mind when he wrote the following:

“The person, by the light of reason and the support of virtue, discovers in the body the anticipatory signs, the expression and the promise of the gift of self, in conformity with the wise plan of the Creator” (VS, no. 48).

Sexual difference, then, far from being merely a biological or anatomical fact, communicates a wealth of truth about the human person! If we have the eyes to see, as Bl. John Paul II urges us to, we’ll see in the human person’s identity as man and woman the “anticipatory signs” of the “gift of self,” or, using the language of the Catechism, we’ll see the call to love, which is the “fundamental and innate vocation of every human being” (CCC, no. 1604).

Sexual difference and marriage

We are now well-poised to understand what sexual difference has to do with marriage. As a recap of Tuesday’s post, marriage is a unique relationship that has a number of essential characteristics (without which marriage wouldn’t be marriage):

  • Marriage is total (gift of self)
  • Marriage is faithful and exclusive (a truthful gift)
  • Marriage is forever (the gift of one’s future)
  • Marriage is life-giving (the gift of one’s fertility)

Sexual difference matters here: it is the ground (the foundation) of the capacity of husband and wife to exchange a mutual, total gift of their entire selves, a gift precisely at the center of what marriage is. Without sexual difference, this gift would not be possible. Put more specifically: the love between husband and wife involves a free, total, and faithful gift of self that not only expresses love but also opens the spouses to receive the gift of a child. No other human interaction on earth is like this!

Sexual difference, then, is not an optional “add-on” to an already existing entity called “marriage” (much like you might choose to add sprinkles to your ice cream – or not). Instead, sexual difference is at the very heart of what marriage is. It’s what capacitates man and woman to give themselves completely to each other as husband and wife. Sexual difference matters for marriage.

Interested in learning more? Check out the DVD “Made for Each Other,” its Viewer’s Guide and Resource Booklet, and all of the Sexual Difference FAQs. Also see the previous blog series on sexual difference.


[1] Even in circumstances when a person expresses ambiguous genitalia or departs from the XX/XY genetic standard, the anomaly is recognized precisely due to its discordance with healthy, normal presentation as male or female.

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