Editor’s Note: The following essay appears in the Fall 2020 issue of Eikon.
“It doesn’t matter who you click with,” declared a 2017 tweet from KLM Royal Dutch Airlines in 2017. Accompanying the tweet were three pairs of rainbow-colored seat belt ends: the first pair had two female ends facing each other, the second two male ends, and the third a male end and a female end. The tweet was fired off with the hashtag “Happy #PrideAmsterdam.”
Natural law has a res ipsa loquitur quality to it that, paradoxically, can make articulating it challenging. That is, articulating common sense or truth-accessible-to-all-by-reason can be difficult. But here is a try.
To begin with the tweet under consideration, one does not need to be a Christian to see that only one combination of seat belt ends will do. Special revelation through Scripture is not required to know no “click” is possible for any other combination. One end is made for the other — fitted together, just so — and that arrangement is exclusive. This we can know through natural law.
Natural law is accessible to every human being because each person is made in God’s own image as a reasoning being. Man participates in the awesome powers of reason and creativity of God the Logos when he exercises and cultivates his faculty to reason. Every human being has this root (Lt. radix) and radical capacity for reason, even the smallest or sickest among us — those whose mental faculties are not yet mature or whose mental faculties have deteriorated. “Thus God made man in his own image,” St. Augustine says, “by creating for him a soul of such a kind that because of it he surpassed all living creatures, on earth, in the sea, and in the sky, in virtue of reason and intelligence; for no other creature had a mind like that. God fashioned man out of the dust of the earth and gave him a soul of the kind I have described.”
Thomas Aquinas teaches that natural law is man’s participation in God’s eternal law. It is our sharing in the truth woven into the fabric, or “deep grammar,” of the created order. It is law “written on [the] hearts,” about which the Apostle Paul writes, while the “conscience also bears witness,” knowable to the Gentiles apart from special revelation. Jewish midrash has a wonderfully telling expression: “If you are told, ‘There is wisdom [hokhma] among the nations,’ believe it. If you are told, ‘There is Torah among the nations,’ do not believe it.” Thus the Jewish category of hokhma, translated as wisdom or prudence, is understood by Rabbi Jonathan Sacks as “the universal heritage of mankind.” Wisdom’s universality makes sense because each person is an image bearer, and thus capable of understanding truth in the created order. Hokhma is a different category than Torah. But of course the truths in hokhma and the Torah do not contradict each other. In fact, they are consonant with each other.
Neither do reason and revelation in Christ Jesus contradict each other. There are surely limits to reason, especially when we remember that we are fallen, sinful beings. The truths in special revelation do exceed the limits of reason — but they are consonant with reason.
Reason is ordered toward good, away from evil. What, then, might reason tell us about marriage and family, and their orientation toward the good and human flourishing?
The design of our bodies tells us that man and woman are made — fitted, even — for each other (a point missed, nearly unbelievably, in the KLM tweet). The design of our bodies also tells us that the union of man and woman is toward the procreation of children who, across cultures and millennia, have been welcome as a good thing: a blessing, a sign of divine favor. Special revelation underscores this: the psalmist proclaims in happy confidence that “children are a heritage from the Lᴏʀᴅ, the fruit of the womb a reward.”
Perhaps it would be good to examine briefly the complementarity of man and woman as father and mother to their children. In an age where fathers (and mothers!) are increasingly absent from their children’s lives through divorce, a break-up following cohabitation, a one-night stand, intentional single parenting, same-sex parenting, “donor” conception, and surrogacy, fathers and mothers have been made to be interchangeable. The distinctives of fathering and mothering have seemed to disappear, reduced flatly to “parenting.”
But research shows that a child needs both his father and mother in order to thrive. Fathers and mothers bring different things to the table. Mothers are more likely to parent their children in a safe and nurturing fashion, while fathers are more likely to encourage their children to take healthy risks, like how to roughhouse safely.
Children who grow up without their fathers in the home are more likely to be impoverished, to be obese, to struggle academically, to abuse drugs and alcohol, to be disciplined in school, to be sexually active as adolescents, and to end up in jail. Looking at girls and boys a little more closely, a girl’s onset of puberty, for example, is about a year later when she is raised by her biological father. Boys, though, seem to be particularly harmed by absent fathers. A boy needs to learn how to be a man primarily from his father, who needs to be faithfully present in his life. As Glenn Stanton explains, the naturalness of womanhood stands in stark contrast to the unnaturalness of manhood: girls’ maturing bodies lead them naturally into womanhood, but the “transition into manhood can only come into being with significant, intentional work by other men. As a behavior, manhood must be learned, proven, and earned. As an identity, manhood must be bestowed by a boy’s father and the community’s larger fraternity of men. His mother can only affirm it. She cannot bequeath it.” Whereas women “must be taught, with great political and ideological pressure, to ignore their womanhood and abandon their children,” manhood for boys, quite the opposite, must be taught, modeled, and embodied.
Not only that, a child needs his biological father and mother to be married to each other to thrive best. Forty years of robust evidence from social science research bears this conclusion. Any other arrangement of adult(s) who is/are parenting the child (single, cohabiting, two of the same sex, more than two [as in a “throuple” or an open relationship], etc.) yields a sub-optimal development of the child — not to the child’s good or flourishing, but away from it. This is unsurprising though increasingly against the orthodoxy of our age. Truly, the deep and innate need and longing to be known, raised, and loved by those who gave us life is written into our being. We need our biological parents to be with us, to raise us, to discipline us, to form us, to love us. Our identity, our making sense of who we are, our very selves, can be fragmented and incoherent without our parents’ faithful presence and love.
If in their children’s lives fathers and mothers have a particular fit, each unique and necessary, the good of marriage as enjoyed by the children a union begets brings us back to marriage itself. C. S. Lewis, grieving the death of his wife, reflected that “[t]here is, hidden or flaunted, a sword between the sexes till an entire marriage reconciles them. . . . Marriage heals this. Jointly the two become fully human. ‘In the image of God created He them.’ Thus, by a paradox, this carnival of sexuality leads us out beyond our sexes.”
This “reconciliation” between man and woman in marriage — this becoming “fully human,” as Lewis calls it, including how the two “shall become one flesh” — also points us beyond our natural state. Marriage between man and wife is taught in Scripture as a picture of Christ and the church. There is a mystery there: a peering behind the veil, a seeing through a glass darkly. But if I may be so bold, might we think of yet another passage from C. S. Lewis where he contemplates the relationship between God and the individual soul, and apply it to Christ and the church as the body of Christ consisting of those souls? Might what we know about marriage and family through reason — and all the wonderful ways in which marriage and family befit us and fit us together — point us to the telos of man as revealed in Scripture?
This signature on each soul may be a product of heredity and environment, but that only means that heredity and environment are among the instruments whereby God creates a soul. I am considering not how, but why, He makes each soul unique. If He had no use for all these differences, I do not see why He should have created more souls than one. Be sure that the ins and outs of your individuality are no mystery to Him; and one day they will no longer be a mystery to you. The mould in which a key is made would be a strange thing, if you had never seen a key: and the key itself a strange thing if you had never seen a lock. Your soul has a curious shape because it is a hollow made to fit a particular swelling in the infinite contours of the Divine substance, or a key to unlock one of the doors in the house with many mansions. For it is not humanity in the abstract that is to be saved, but you — you, the individual reader, John Stubbs or Janet Smith. Blessed and fortunate creature, your eyes shall behold Him and not another’s. All that you are, sins apart, is destined, if you will let God have His good way, to utter satisfaction. The Brocken spectre ‘looked to every man like his first love’, because she was a cheat. But God will look to every soul like its first love because He is its first love. Your place in heaven will seem to be made for you and you alone, because you were made for it — made for it stitch by stitch as a glove is made for a hand.
Adeline A. Allen is Associate Professor of Law at Trinity Law School.
 Robert P. George, “Natural Law, God and Human Dignity,” in The Cambridge Companion to Natural Law Jurisprudence, eds. George Duke and Robert P. George (New York: Cambridge University Press, 2017), 63–68; Samuel Gregg, Reason, Faith, and the Struggle for Western Civilization (Washington, DC: Regnery Gateway, 2019), 40–41; Rabbi Jonathan Sacks, Covenant & Conversation: Genesis (Jerusalem: Maggid Books, 2009), 290.
 See George, “Natural Law,” 63–68.
 Saint Augustine, City of God, trans. Henry Bettenson (London: Penguin Books, 2003), 503.
 Thomas Aquinas, Summa Theologiae, trans. Alfred J. Freddoso (South Bend: St. Augustine’s Press, 2009),
I–II, Q. 91, A. 2.
 I borrow this lovely phrase “deep grammar” from Rabbi Jonathan Sacks’ commentary on prayer. Sacks, Genesis, 188.
 Romans 2:15; Gregg, Reason, 41.
 Sacks, Genesis, 290.
 Sacks, Genesis, 290.
 See Sacks, Genesis, 290.
 Sacks, Genesis, 290.
 Robert Royal, “A Delicate Tapestry,” review of Reason, Faith, and the Struggle for Western Civilization, by Samuel Gregg, Claremont Review of Books, Spring 2020; see Gregg, Reason, 46–51.
 See George, “Natural Law,” 66.
 Royal, “Delicate Tapestry”; see Gregg, Reason, 46–51.
Josef Pieper says, “[B]elief has the extraordinary property of endowing the believer with knowledge which would not be available to him by the exercise of his own powers.” Josef Pieper, An Anthology (San Francisco: Ignatius Press, 2011). Thus R. R. Reno comments, “Faith enlarges our capacity for truth.” R. R. Reno, “While We’re at It,” First Things, August/September 2020.
 Aquinas, Summa Theologiae, I–II, Q. 94, A. 2; see also John Finnis, “Aquinas and Natural Law Jurisprudence,” in The Cambridge Companion to Natural Law Jurisprudence, eds. George Duke and Robert P. George (New York: Cambridge University Press, 2017), 17, 18–19; George, “Natural Law,” 57, 59.
 An excellent natural law account of the good of marriage as the conjugal union of one man and one woman, What Is Marriage? Man and Woman: A Defense by Robert P. George (who is a contributor to the present issue of the Journal), Sherif Girgis, and Ryan T. Anderson, is worthy of every reader’s serious study. (New York: Encounter Books, 2012).
 Psalm 127:3.
 See Anthony Esolen, “The Boy Genius: Finding Him Again Through the Patriarchal Group,” Touchstone Magazine, accessed July 18, 2020, https://www.touchstonemag.com/archives/article.php?id=32-02-029-f, for a remarkably insightful observation of how this safe and nurturing quality in mothers are not unrelated to women’s tendency as a sex not to fall on the extreme end of the spectrum of genius, for example, because being a genius also likely means taking no heed of danger while being utterly lost in thought — which nature cannot afford, because it would mean that small children under the care of mothers would be in grave danger or perish. “Nature is conservative with females, because to them is given the whole biological future of the race. She is devil-may-care with males, because they are demographically expendable.” Esolen calls the teaching style of female teachers, for example, “a safe space, the walled garden.”
 “The Importance of Fathers (According to Science),” The Art of Manliness, accessed July 18, 2020, www.artofmanliness.com/articles/the-importance-of-fathers-according-to-science/.
 The Art of Manliness, “The Importance of Fathers.”
 Ryan T. Anderson, Truth Overruled: The Future of Marriage and Religious Freedom (Washington, DC: Regnery Publishing, 2015), 151.
 See Kay Hymowitz, “Disentangling the Effects of Family Structure on Boys and Girls,” Institute for Family Studies, accessed August 4, 2020, https://ifstudies.org/blog/disentangling-the-effects-of-family-structure-on-boys-and-girls.
 “Manhood Is Not Natural,” Public Discourse, accessed July 18, 2020, https://www.thepublicdiscourse.com/2017/
12/20272/; see also Anthony Esolen, Defending Boyhood: How Building Forts, Reading Stories, Playing Ball, and Praying to God Can Change the World (Charlotte: TAN Books, 2019), 26–27.
 Public Discourse, “Manhood Is Not Natural.” See also Esolen, Defending Boyhood, 13–37, 81–97; Touchstone Magazine, “The Boy Genius.”
 Anderson, Truth Overruled, 148–52; Alysse ElHage, “How Marriage Makes Men Better Fathers,” Institute for Family Studies, accessed July 18, 2020, https://ifstudies.org/blog/how-marriage-makes-men-better-fathers; David C. Ribar, “Children Raised Within Marriage Do Better on Average. Why?”, Child & Family Blog, accessed July 27, 2020, https://www.childandfamilyblog.com/child-development/children-marriage-do-better-why/; Ana Samuel, “The Kids Aren’t All Right: New Family Structures and the ‘No Differences’ Claim,” Public Discourse, accessed July 18, 2020, https://www.thepublicdiscourse.com/2012/06/5640/.
To say this is not to diminish the heroism and selflessness on the part of parents who adopt their children, but to work out the implications of data that show that children do best when raised by their married biological father and mother. Anderson, Truth Overruled, 151. A special word is warranted about a rising trend: Especially in contrast to adoption, wherein adoptive parents step in and redeem an already broken situation for the child, increasingly other parenting schemes intentionally deprive the child of one or both of his biological parents, as in the case of, for example, donor conception, same-sex parenting, and surrogacy. See, for example, Anderson, Truth Overruled, 148–52, 152–72; Adeline A. Allen, “Surrogacy, Love, and Flourishing,” Public Discourse, accessed July 18, 2020, https://www.thepublicdiscourse.com/2019/09/56158/; Alana S. Newman, “What Are the Rights of Donor-Conceived People?” Public Discourse, accessed July 18, 2020, https://www.thepublicdiscourse.com/2013/08/10511/.
 Anderson, Truth Overruled, 149.
 Anderson, Truth Overruled, 148–58.
 Melissa Moschella, To Whom Do Children Belong? Parental Rights, Civic Education, and Children’s Autonomy (Cambridge: Cambridge University Press, 2016), 21–48; Melissa Moschella, “The Wrongness of Third-Party Assisted Reproduction: A Natural Law Account,” Christian Bioethics 22, no. 2 (May 2016): 104–21, https://doi.org/10.1093/cb/cbw008; “My Daddy’s Name Is Donor,” Institute for American Values, accessed July 20, 2020, https://canavox.com/wp-content/uploads/2017/06/American-Values_Donor.pdf, 5–14.
 Moschella, To Whom Do Children Belong?, 21–48; Moschella, “Wrongness of Third-Party Assisted Reproduction,” 104–21.
 C.S. Lewis, A Grief Observed (New York: Harper One, 2001).
 Genesis 2:24.
 C.S. Lewis, The Problem of Pain (New York: Harper One, 1996), 151–52 (emphasis added).
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