The most common argument in favor of same-sex marriage (gay marriage) is that homosexuals deserve the same rights, including the right to marriage, as anyone else. My reply, from the point of view of Catholic theology, is that every right has natural limits. The debate around same-sex marriage does not really turn on whether everyone deserves the same rights — of course they do. Every human person deserves, and in fact possesses before the eyes of God, the same set of fundamental human rights. But every fundamental human right has an essential nature, that is to say an inherent meaning, within human life. And whatever is beyond the limits of that nature, of that meaning, is not a part of that right.

For example, we all have a natural right to freedom of speech. But that right does not extend to a verbal threat to do violence to someone. Nor does the right to freedom of speech justify any sin, such as teaching heresy or lying. We all have a right to life, but this right does not extend to taking one’s own life. We all have a right to the pursuit of happiness, but this does not justify grave harm to others as a means to that pursuit.

Every human right has natural limits because each right has an essential nature, an inherent meaning. The right to freedom of speech is distinct from the right to life because each right pertains only to certain types of actions, to one meaning and not another. In the same way, each right extends only within its own meaning: free speech does not include verbal assault; the right to seek to be happy does not justify grave sins of any kind.

What are the natural limits to the right of marriage? I think we would all agree that one cannot marry, under law or religion, if one is too young, or mentally incompetent. The secular laws also acknowledge that a person should only have one spouse; bigamy is illegal. Does the right to marriage include the right to an “open marriage”, in which the spouses have sexual relations with persons other than their spouse? Certainly not. Adultery is acknowledged to be gravely immoral by reasonable persons in every society, regardless of their religion. Adultery is not generally illegal in the United States at the present time, but it is illegal under the UCMJ (military law), and carries a maximum penalty of one year imprisonment.

The fundamental question at issue in the same-sex marriage debate is whether the natural right to marriage includes marrying someone of the same gender. The answer for all Christians ought to be the same as Jesus himself plainly taught:

[Matthew]
{19:4} And he said to them in response, “Have you not read that he who made man from the beginning, made them male and female?” And he said:
{19:5} “For this reason, a man shall separate from father and mother, and he shall cling to his wife, and these two shall become one flesh.
{19:6} And so, now they are not two, but one flesh. Therefore, what God has joined together, let no man separate.”

[Mark]
{10:6} But from the beginning of creation, God made them male and female.
{10:7} Because of this, a man shall leave behind his father and mother, and he shall cling to his wife.
{10:8} And these two shall be one in flesh. And so, they are now, not two, but one flesh.
{10:9} Therefore, what God has joined together, let no man separate.”

[Luke]
{16:14} But the Pharisees, who were greedy, were listening to all these things. And they ridiculed him.
{16:15} And he said to them: “You are the ones who justify yourselves in the sight of men. But God knows your hearts. For what is lifted up by men is an abomination in the sight of God.
{16:16} The law and the prophets were until John. Since then, the kingdom of God is being evangelized, and everyone acts with violence toward it.
{16:17} But it is easier for heaven and earth to pass away, than for one dot of the law to fall away.
{16:18} Everyone who divorces his wife and marries another commits adultery. And whoever marries her who has been divorced by her husband commits adultery.

Jesus Christ taught:

1. God created humanity in two genders, male and female, for a purpose, namely,
2. that marriage would be based on the union of man and woman as one flesh.
3. He also taught that no one has the authority or ability to contradict this definition of marriage.
4. For what human society considers exalted, is sometimes an abomination in the eyes of God.

The Roman Catholic Magisterium teaches:

“The Church’s teaching on marriage and on the complementarity of the sexes reiterates a truth that is evident to right reason and recognized as such by all the major cultures of the world. Marriage is not just any relationship between human beings. It was established by the Creator with its own nature, essential properties and purpose. No ideology can erase from the human spirit the certainty that marriage exists solely between a man and a woman, who by mutual personal gift, proper and exclusive to themselves, tend toward the communion of their persons. In this way, they mutually perfect each other, in order to cooperate with God in the procreation and upbringing of new human lives.”

“The natural truth about marriage was confirmed by the Revelation contained in the biblical accounts of creation, an expression also of the original human wisdom, in which the voice of nature itself is heard. There are three fundamental elements of the Creator’s plan for marriage, as narrated in the Book of Genesis.

“In the first place, man, the image of God, was created ‘male and female’ (Gen 1:27). Men and women are equal as persons and complementary as male and female. Sexuality is something that pertains to the physical-biological realm and has also been raised to a new level – the personal level – where nature and spirit are united.

“Marriage is instituted by the Creator as a form of life in which a communion of persons is realized involving the use of the sexual faculty. ‘That is why a man leaves his father and mother and clings to his wife and they become one flesh’ (Gen 2:24).

“Third, God has willed to give the union of man and woman a special participation in his work of creation. Thus, he blessed the man and the woman with the words ‘Be fruitful and multiply’ (Gen 1:28). Therefore, in the Creator’s plan, sexual complementarity and fruitfulness belong to the very nature of marriage.

“Furthermore, the marital union of man and woman has been elevated by Christ to the dignity of a sacrament. The Church teaches that Christian marriage is an efficacious sign of the covenant between Christ and the Church (cf. Eph 5:32). This Christian meaning of marriage, far from diminishing the profoundly human value of the marital union between man and woman, confirms and strengthens it (cf. Mt 19:3-12; Mk 10:6-9).

“There are absolutely no grounds for considering homosexual unions to be in any way similar or even remotely analogous to God’s plan for marriage and family. Marriage is holy, while homosexual acts go against the natural moral law.”
(CDF, Cardinal Joseph Ratzinger, Considerations Regarding Proposals….)

Jesus Christ, His Church, and the natural law that is inherent to human nature all teach one and the same truth: that marriage is — by its very nature — restricted to the union of a man with a woman. Therefore, same-sex marriages are not a true type of marriage, neither under natural law, nor as a Sacrament.

by
Ronald L. Conte Jr.
Roman Catholic theologian and
translator of the Catholic Public Domain Version of the Bible.