God created marriage between one man and one woman to show the mystery between Christ and the Church. The Judeo/Christian Worldview of marriage has led, and I pray will still lead the culture, in the definition of marriage. It shows how Christ is faithful even when we are not faithful. He will never divorce the Church or walk away. He loves the Elect and is beautifying us.
I was listening to Andy Lewis, pastor of Mitchell Road Presbyterian Church in Greenville, SC. preach on Revelation. He pointed out that Solomon messed up God’s design for marriage. In 1215 the Catholic Church made marriage a sacrament. Protestants only have the Lord’s Supper and Baptism as a sacrament. In Roman times people did not marry for love. A Roman Senator was kicked out of the senate for kissing his wife in public. The French philosopher Montesquieu, said that anyone who is in love with his wife is too dull for other women to love him or something like that. In the 17th and 18th centuries philosophers encouraged people to marry for love. But even with the evolving thoughts about marriage it is still the design of God.
As Christians we can set the example in our marriages for unbelievers. We need Jesus in order to do that!