From all eternity, Almighty God has conceived of our salvation, and the image in His mind has been a heavenly wedding, the marriage feast of Christ the Bridegroom with His spouse, the Church. Thus He created us male and female, and in the fullness of time He made the stable and fruitful communion of man and woman into a sacrament of salvation.
Therefore, people love weddings. And not just for sentimentality’s sake. We love weddings because they show us an image of heaven. As the Fathers of Vatican II put it:
As God of old made Himself present to His people through a covenant of love and fidelity, so now the Savior of men and the Spouse of the Church comes into the lives of married Christians through the sacrament of matrimony. He abides with them thereafter so that just as He loved the Church and handed Himself over on her behalf, the spouses may love each other with perpetual fidelity. (Gaudium et Spes 48)
Beautiful. But we also have to confront the messier side of this business. If our First Parents had never fallen from grace—if sin had never entered the world—then no one would ever fornicate, or marry imprudently, or cheat, or divorce, or do any other destructive or unchaste thing. But…