Same-Sex Marriage and the Natural Law

The vertical dimension of human existence links man to his Creator. He is made in the image of God, intelligent and free. … It is because man is a contingent, finite, intelligent, free creature of God that he is responsible to him for his actions.


(Editor’s note: Rev. Robert A. O’Donnell, C.S.P., died in December 2012. This may have been one of  his last writing efforts. HPR wishes to honor his memory in publishing this article, thanking him for his many years of service to the Church. Please remember him in your prayers. May he rest in peace.)

Unless you can profess with the author of this article the following creed, which was composed by the Fathers of the Council of Nicea in 325 A.D., and which is professed by Catholics around the globe every Sunday at Mass, please do not read further into this article; it will make no sense to you at all:

“I believe in one God, the Father almighty, maker of heaven and earth, of all things, visible and invisible…” 

Christians believe that everything which exists was created by God: the heavens and the earth, the seas and the mountains, plants, insects, animals, and human beings. And we believe that human beings were created by God in his own image, that is to say, humans have been endowed by God with intelligence and free will, and they are responsible to him for using their intellects to understand the proper relationship between the Creator and what he has created. And further, they are responsible to him for always making correct and moral, free decisions. These are the points which this article will be addressing.

The Creator, like Bramante and Michelangelo who designed St. Peter’s Basilica and its Dome, must have had a plan for all that he has brought into being out of nothing. An intelligent creature cannot expect to understand exhaustively God’s plan for everything which he has brought into being out of nothing, for God’s unseen creation is much broader than what is seen. Still, by examining what he sees—the heavens and the earth with all its creatures—man can come to an understanding of part of the divine, creative plan. That part of the divine, eternal plan which man can come to know by using his intellect is called “The Natural Law.”

The Ten Commandments, which God entrusted to Moses on Mt. Sinai, are examples of positive laws which make explicit what is already implicit in the natural law: that the creature should praise the Creator; that children should respect their parents; that one should not kill nor steal nor commit adultery. These are all precepts of the natural law which man can discover from an intelligent examination of that part of creation which can be seen by him.

No one has written more clearly or concisely about the natural law than St. Thomas Aquinas, that peerless 13th century philosopher-theologian. In his master work, Summa Theologiae (I-II, q. 94), he offers us the following points concerning the natural law:

  1. The natural law is that part of the divine, eternal law which applies to human beings and which can be understood by them.
  2. The human intellect operates on two distinct levels, on a speculative level and on a practical level. It is on the speculative level that the mind pursues the positive sciences: mathematics, physics, chemistry, biology, psychology, etc. It is on the practical level that the mind discovers the natural law, and judges the morality of human acts in the light of it.
  3. The first, self-evident, indemonstrable principle of the natural law which is “known naturally” by every sane, mature mind is: “good is to be done and evil is to be avoided.” Then, St. Thomas adds “all other precepts of the natural law are based upon this.”
  4. The natural law is the same for all human beings, and it is unchangeable.
  5. The natural law is “written in the hearts of men which iniquity itself cannot efface” (from the “Confessions of St. Augustine,” ii). After quoting St. Augustine, St. Thomas comments: “But the law, which is written in men’s hearts, is the natural law. Therefore, the natural law cannot be blotted out.”

Let us pause here, and approach our subject from a slightly different point of view. Implicit in all of St. Thomas’s writings about man is the fact that there is a dual dimension to human existence: a horizontal dimension and a vertical dimension. On the horizontal dimension, man is seen as a social being, dependent for his being and for his well-being on the various human societies to which he belongs. The first and most basic society to which the human person belongs is the family. Other societies upon which he depends are the church, the school, the neighborhood, the town, the country, and myriads more.

The vertical dimension of human existence links man to his Creator. He is made in the image of God, intelligent and free. God is the necessary, infinite being, which means that he has neither beginning nor ending, and that his being is absolutely without any limitation. Man, on the other hand, is a contingent, finite being which means that he has had a beginning in time and that his being has definite limitations. It is because man is a contingent, finite, intelligent, free creature of God that he is responsible to him for his actions.

Any authentic, ethical system must take both of these dimensions into consideration.

Some ethicists today recognize only the horizontal dimension of human existence, and, accordingly, eliminate God, and man’s responsibility to him, from their systems. To them, the natural law has no meaning. However, it is only when both the horizontal and vertical dimensions of the human being are recognized, that that part of the eternal law, which we call the “natural law,” is discovered.

On the horizontal level, Aristotle (384–322 B.C.) states in Greek, and St. Thomas Aquinas repeats in poetical Latin, “Homo homini amicus” (“Man is a friend to his fellowman”). It is a precept of the natural law that God certainly intends human beings to live in peace with one another. He does not will conflicts and wars (which began with the murder of Abel by his brother Cain). These aberrations in human societies are caused by the sins which men freely commit in violation of the natural law. Friendships among men and women are certainly willed by their Creator, and countless classical authors, from Cicero to Blessed John Henry Cardinal Newman, have extolled its merits. Yet, the natural law permits sexual unions as expressions of friendship exclusively between a husband and a wife within the state of a valid marriage.

On June 24, 2011, New York became the sixth of the 50 states to legalize same-sex marriage. This human, positive law is a clear violation of precepts of the divine, natural law. Scripture’s opening proclaims that: “God created man in the image of himself, in the image of God he created him. Male and female he created them. God blessed them and said to them, ‘Be fruitful, multiply and fill the earth and conquer it’” (Gen 1:27-28).

It is obvious to everyone that the male and female human bodies complement one another sexually, and possess together the power to regenerate human life. It is equally obvious that no such complementarity, or regenerative power, exists between bodies of the same sex.

The natural law also mandates that sexual intercourse take place exclusively between a husband and wife within a stable, monogamous state of marriage. This is seen from the fact that the human newborn is the most helpless and most dependent of all newborn animal life. A pony is up on all fours just minutes after its birth, accompanying its mother everywhere she goes. It takes a human newborn a year or more to begin to stand on its legs, and an additional 15 to 20 years to mature sufficiently to separate itself from father and mother, and start an independent life of its own.

The Catechism of the Catholic Church has this to say about homosexuality:

Basing itself on Sacred Scripture, which depicts homosexual acts as acts of grave depravity, tradition has always declared that “homosexual acts are intrinsically disordered.” They are contrary to the natural law. They close the sexual act to the gift of life. They do not proceed from a genuine affective and sexual complementarity. Under no circumstances can they be approved.  (#2357)  {cf. Genesis 19:1-29; Romans 1:24-27; 1 Cor. 6:10; 1 Tim 1:10}

The number of men and women who have deep-seated homosexual tendencies is not negligible. They do not choose their homosexual condition; for most of them it is a trial. They must be accepted with respect, compassion and sensitivity. Every sign of unjust discrimination in their regard should be avoided. These persons are called to fulfill God’s will in their lives and, if they are Christians, to unite to the sacrifice of the Lord’s cross the difficulties they may encounter from their condition. (#2358)

The two key sentences in the above citations from the Catechism of the Catholic Church are:  “They (consensual homosexual acts) are contrary to the natural law” and “Under no circumstances can they be approved.”

Many Catholics today, together with some of their priests, find it very difficult to accept this clearly stated position of their Church. This is for a variety of reasons:

  1. “Not a negligible number of them” are themselves oriented toward a same-sex attraction. This includes some sections of the clergy who, while observant of their vow of celibate chastity, are homosexually oriented.
  2. Others among the clergy, while they themselves are heterosexually oriented, know a relative or an acquaintance that is living in a homosexually oriented lifestyle.
  3. Same-sex marriages are becoming more tolerated in American and European societies. That this mentality has infected the Episcopal Church in the United States is evidenced by the election of Gene Robinson, an openly practicing homosexual, to be bishop of New Hampshire.
  4. Some, who have difficulty accepting this teaching of the Church, appeal to the ancient Latin triptych: “Lex orandi, lex credendi, lex vivendi” (“as we pray, so we believe, so we live”). They believe that they are pursuing a prophetic role, presaging a time when the Church will reverse its teaching on this point.

Of course, there is nothing new about Catholics questioning the teachings and practices of their Church. The history of Christianity is pockmarked by schisms and heresies. The author of the Epistle to the Hebrews (13:9) cautioned his readers not to accept the “strange teachings” of their age. Subsequent centuries brought fresh dissensions, from the Judaic heresies of the first century through the Arianism, Nestorianism, and Pelagianism of the early Middle Ages, through the Protestantism and Jansenism of the late Middle Ages, to the rationalism and relativism of today.

Still, by the grace of God, the Church seems able always to survive these batterings from within and outside its ranks. In this irenic 21st century, unimaginable are the hideously unjust burnings at the stake which victimized Joan of Arc at Rouen in 1431, and the two Italian Dominican friars, Girolamo Savonarola at Florence in 1498, and Giordano Bruno at Rome in 1600. Since the 1960s, when Pope John XXIII inserted the Catholic Church into ecumenical dialogues, “schismatics and heretics” have become “our separated brethren.” And we are seeking reconciliation by dialoguing with them across a table. Again, by the grace of God, reconciliations with “separated brethren” were beginning to surface as recently as during the Ratzinger papacy.

Bishop Fulton J. Sheen, the leading American evangelist of the 20th century, liked to coin clever, catch phrases to illustrate his preachings. An oft-quoted favorite of his to illustrate the natural law was: “Right is right, if nobody’s right; and wrong is wrong, if everybody’s wrong.”  Aurea dicta! (Golden words!)

Rev. Robert A. O'Donnell, CSP About Rev. Robert A. O'Donnell, CSP

We are sad to report that Father Robert A. O'Donnell, CSP, died Nov. 26, 2012, at the Paulist Residence in Manhattan, before his article could be published on HPR.

He was a member of the Missionary Society of St. Paul the Apostle for 67 years, and was 88 years old at the time of his death.

Father O'Donnell was born in 1924 in Greenwood, RI. He was ordained to the priesthood as Paulist Father on May 1, 1951. Father O'Donnell earned both a BA and MA degree from St. Paul's College in Washington, D.C., and a PhD from the University of Louvain in Belgium.

Father O'Donnell's first priestly assignment was as associate pastor at Good Shepherd Church in New York City from June through September of 1951. He then went to study in Belgium from 1951-55, when he ministered to what was then the Newman Club at the University of Texas at Austin. Father O'Donnell returned to his alma mater of St. Paul's College to teach from 1956-62. He then served as associate pastor at the Church of Santa Susanna in Rome while teaching at Loyola University and serving as an NBC correspondent from 1962-66.

After returning stateside, Father O'Donnell served as the director of the Paulist radio, television and film apostolate based in New York City from 1966-68 before heading back to St. Paul's College as president and superior, serving from 1968-70. Rome again beckoned, and Father O'Donnell served as superior and procurator general from 1970-78.
He served as director of the Paulist Development Office based in New York from 1978-84, when he returned to Rome to study at the Pontifical University until 1985. He then joined the pastoral staff at Santa Susanna until heading to Switzerland in 1987 to serve with the Ecumenical Institute of the World Council of Churches in Bossey. From 1988-91, Father O'Donnell served at the Tantur Ecumenical Institute in Jerusalem.

Father O'Donnell entered senior ministry status at the Paulist Residence in New York City in 1991, but continued to serve as a professor of philosophy at St. John Neumann Seminary College in Dunwoodie, NY.

Please remember him in your prayers. May he rest in peace.


  1. To convince non-Catholics, we need a similar article that is not achored in Catholic teaching. Can the same line of reasoning be derived from Aristotle?


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