Why does the Catholic Church teach that marriage can exist only between a man and a woman? The truth that marriage can only exist between a man and a woman is woven deeply into the human spirit. This truth has been confirmed by divine Revelation in Sacred Scripture. The natural structure of human sexuality makes man and woman complementary partners for expressing conjugal love and transmitting human life.
Only a union of male and female can express the sexual complementarity willed by God for marriage. This unique complementarity makes possible the conjugal bond that is the core of marriage.
A same-sex union contradicts the nature and purposes of marriage. It is not based on the natural complementarity of male and female. It cannot achieve the natural purpose of sexual union, that is, to cooperate with God to create new life.
Because persons in a same-sex union cannot enter into a true conjugal union, it is wrong to equate their relationship to a marriage. What unique contributions does marriage between a man and woman make to society? Marriage is the fundamental pattern for male-female relationships. It contributes to society because it models the way in which women and men live interdependently and commit to seek the good of each other. The marital union also provides the best conditions for raising children: namely, the stable, loving relationship of a mother and father present only in marriage.
The state recognizes this relationship as a public institution in its laws because the relationship makes a unique and essential contribution to the common good. Ideas about marriage have changed over the years. The institution of marriage has experienced many developments. Some of these are related to our contemporary understanding about the equality of men and women.
