Can a man marry a man? Can a woman marry a woman? Can a man simultaneously marry several women, or a woman several men? Can a man simultaneously marry several men, or a woman several women? Can a man marry his sister or his mother? His brother or his father? Can a woman marry her brother or father? Her sister or mother?

All of these questions are now relevant in our culture. They cannot be properly answered unless we know what marriage is. As Catholics, we have an incredibly rich body of teaching to draw from in order to understand the meaning and purpose of marriage. Let us begin with a basic definition drawn from Canon Law and the Second Vatican Council.

Marriage is the intimate, exclusive, indissoluble communion of life and love entered into by man and woman at the design of the Creator for the purpose of their own good and the procreation and education of children. This covenant between baptized persons has been raised by Christ the Lord to the dignity of a Sacrament.

Intimate communion of life and love: Marriage is the closest and most intimate of human friendships. It involves the sharing of the whole of a person's life with his/her spouse. Marriage calls for a mutual self-surrender so intimate and complete that spouses - without losing their individuality - become "one," not only in body, but in soul.

Exclusive communion of life and love: As a mutual gift of two persons to each other, this intimate union excludes such union with anyone else. It demands the total fidelity of the spouses. This exclusivity is essential for the good of the couple's children as well.

Indissoluble communion of life and love: Husband and wife are not joined by passing emotions or mere erotic inclination which, selfishly pursued, fades quickly away. They are joined in authentic conjugal love by the firm and irrevocable act of their own will. Once their mutual consent has been consummated by genital intercourse, an unbreakable bond is established between the spouses. For the baptized, this bond is sealed by the Holy Spirit and becomes absolutely indissoluble. Thus, the Church does not so much teach that divorce is wrong, but that divorce is impossible, regardless of its civil implications.

Entered by man and woman: The complementarity of the sexes is essential to marriage. It's not that two men (or two women) could marry, but the Church won't "let them." If we understand what marriage is, we will see very clearly that it is impossible for members of the same sex to marry.

At the design of the Creator: God is the author of marriage. He inscribed the call to marriage in our very being by creating us as male and female. We, therefore, are not able to change the nature and purposes of marriage.

For the purpose of their own good: "It is not good that the man should be alone" (Gen 2:18). Conversely, it's for their own good, for their benefit, enrichment, and, ultimately, their salvation, that a man and woman join their lives in marriage.

Procreation and education of children: Children are not added on to marriage and conjugal love, but spring from the very heart of the spouses' mutual self-giving, as its fruit and fulfillment. Intentional exclusion of children, then, contradicts the very nature and purpose of marriage.

Covenant: While marriage involves a legal contract, a covenant goes beyond the minimum rights and responsibilities guaranteed by a contract. A covenant calls the spouses to share in the free total, faithful, and fruitful love of God. For it is God who, in the image of his own Covenant with his people, joins the spouses in a more binding and sacred way than any human contract.

The dignity of a sacrament: Marriage between baptized persons is an efficacious sign of the union between Christ and the Church, and, as such, is a means of grace. That is, marriage - in as much as the union of man and woman truly symbolizes Christ's love for the Church - really communicates Christ's love to the spouses and, through them, to the whole world.