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The One-Flesh Union


Sherif Girgis

The preparatory document for October’s Vatican synod on the family asks what vision of the human person lies behind the natural law understanding of marriage. To help us think about this issue, we might first ask what natural law is.

The Catechism of the Catholic Church states, “The natural law, present in the heart of each man and established by reason, is universal in its precepts and its authority extends to all men” (1956). It is a participation in God’s own law, allowing us to know moral truths by reason, even while Church teaching informs our conscience and guides us along the right path.

However, natural law is not just a Christian concept. Plato and Aristotle began to develop a tradition of moral philosophy long before the birth of Jesus. They came so close to Hebrew and Christian moral insights that some early Church Fathers wondered whether Plato had received private revelations. Since then, countless Christian thinkers have drawn from Greek philosophy to develop insights on natural law, even to this day.

It is important to understand that the moral law is not meant to limit us; it guides us in the way of truth and love. Far from being arbitrary, it reflects the truth about the human person and in this way helps build communion among people who share a human nature. To break the moral law is to invite confusion and division.

In response to the synod preparatory document’s question about natural law and marriage, let’s begin with the human person. We are not spirits in bodily costumes. As persons, we are our living bodies, either male or female. For this reason, spousal love — which seeks total union with the beloved — calls for a union of bodies, as well as hearts and minds.

But what makes for bodily union? It isn’t emotion or pleasure alone — bonds of friendship can give us these. Rather, it requires bodily cooperation toward a single end. After all, you are personally “one flesh,” one body, by the fact that your own physical systems cooperate together for a single end: your life.

A “one-flesh” union is also possible between two adults in one specific way. In the marital act, a man and woman are coordinated toward a single bodily end: new life. In this way, the life-giving act becomes the love-making act — a seal of their committed union of heart and mind by a true bodily union. In fact, marriage is uniquely deepened by family life precisely because the act that makes marital love is also the kind that makes new life. This all-encompassing union, and its orientation toward bringing new human beings to maturity, requires an all-encompassing commitment that is permanent and exclusive.

So many features of marriage — its commitment to permanence and exclusivity, openness to life and unitive significance — are grounded in our bodies, as male and female. But as polls indicate, many Catholics today — and many more outside the faith — doubt that a person’s sexual embodiment as male or female matters much in marriage. They ask: Isn’t it enough that two people are in love or emotionally attached? Yet those who ask this question should themselves ask a few more.

Why should a union based on certain feelings be pledged to permanence, as opposed to lasting only as long as the feelings do? Why should marriage be a union of two, if three can share love? Why should the spouses “forsake all others,” if a sexually “open” union enhances emotional fulfillment? Why should the bond be sexual at all, if its promise lies in emotional satisfactions? Answers to these questions may reveal more support for traditional marital norms than polls suggest. In the end, natural law shapes our thinking even when we try to deny it.

Plato and Aristotle knew that to honor marriage was to affirm the beauty and goodness of embodied love and new human life. We also know that honoring the natural law of marriage can lead us, by grace, to supernatural life, where all are made one body, one spirit in Christ.

SHERIF GIRGIS, a law student at Yale and doctoral student in philosophy at Princeton, is coauthor of What Is Marriage? Man and Woman: A Defense (Encounter Books).