Why does the Catholic Church say marriage is between one man and one woman?

Two reasons for upholding the Church’s teaching on marriage, namely, that marriage can only be the union of one man and one woman.

First, we have what Jesus taught us and is written in Matthew, “Have you not read that from the beginning the Creator 'made them male and female’ and said, 'For this reason a man shall leave his father and mother and be joined to his wife, and the two shall become one flesh'?” (Mt 19:5-6) This was in response to a question on divorce, but Jesus is clearly stating that marriage is between one man and one woman. If there is any confusion to Jesus’ words or intent, we just need to look at the disciples’ response a few verses later, "If that is the case of a man with his wife, it is better not to marry." (Mt 19:10)

At that time, divorce was very common as was polygamy and homosexuality. We see aberrant sexual behavior described in the first chapter of St Paul’s letter to the Romans (Rom 1:24-28) and in other non-Church writings. But, Jesus clearly spells out “male and female” and defines a marriage covenant that is for a lifetime, between one man and one woman. Basically, man and woman are made for each other both bodily and spiritually!

Secondly, God created marriage to carry on God’s work of creation. We see this when Jesus pointed back at Genesis where we have two descriptions of God’s intent at the time of creation. In the first chapter we have God stating, “Be fertile and multiply; fill the earth and subdue it.” (Gen 1:28) And, in the second chapter, “a man leaves his father and mother and clings to his wife, and the two of them become one body.” In the latter case, this is the description that God intended a man and woman to have intercourse. God is saying through these two statements (as Christ reinforced), that sex is intended to be between a man and woman and the purpose is to generate new life. We know deep in our hearts that sex is all about creating new life.

Finally, the Catechism that is an expression of Sacred Scripture and Sacred Tradition is full of rich descriptions of marriage and God’s intent. (For example, CCC 1602-1620) In these paragraphs on marriage are several statements reinforcing what I stated above. For example, CCC 1616 refers to St Paul’s letter to the Ephesians where Paul writes: “For this reason a man shall leave his father and mother and be joined to his wife, and the two shall become one. This is a great mystery, and I mean in reference to Christ and the Church.” (CCC 1616 & Eph 5:31-32)

Why does the Catholic Church say birth control is wrong?

The Church teaches that artificial birth control is wrong. Here are three reasons for this teaching.

First, artificial birth control limits the charity (self-giving love) of the conjugal act. It eliminates or attempts to eliminate fertility. In some cases such as sterilization, it completely eliminates fertility. As a result, one is not giving fully and therefore not loving completely as God intended but rather withholding a significant, if not the most significant part of the conjugal act.

Secondly, the conjugal act must be open to life. After all, sexual intercourse is an expression of a life-giving love. The purpose of the conjugal act is to produce semen in an attempt to find an ovum thereby creating life. This is a wonderful gift from God, i.e. that humanity can participate in “creation.” So, the second significant reason artificial birth control is wrong is that it is used to prevent this creation of life, i.e. it indicates one is not open to life during the conjugal act.

Thirdly, artificial birth control interferes with one of the most significant biological aspects of the body. Basically, it violates the body and what the body is trying to do through sex. The reason sex usually “feels good” is because the body is inclined to procreate, to have the semen produced so that it tries to find the ovum. Artificial birth control is an attempt to violate what the body is biologically trying to do. God made the bodies of man and woman to have and desire sex. Artificial birth control changes all this. Sex now becomes something else, i.e. a way to use sex primarily for pleasure.