The Catechism says the “vocation to marriage is written in to the very nature of man and woman as they came from the hand of the creator.” If that is true, why do people have such a difficult time understanding what marriage is and that it can only be between a man and a woman?
St. Thomas Aquinas taught two things are required to understand natural law: The first is ordered thought — rational and deductive — and the second is knowledge — facts, an awareness that reality exists. Today, many tend to just form opinions based on our experience — what we feel is right or wrong.
But people can still see the reality of marriage if we look through the eyes of a person untouched by relativism — the child knows reality. Remember, Christ prayed “Father, you have hidden these things from the wise and learned and revealed them to the childlike." (Luke 10:21) Who are the wise and learned? We are. That requires humility.
We all can experience God’s plan for creation by reflecting on our own natural desire to know where we came from, who is our mother and father and a longing to be loved by them. When that love is withheld, or we don’t know our mom or dad, we feel a real loss and wonder about them.
That is why experience tells us and the Church teaches that we have a natural obligation to promote laws, institutions and curricula that encourage men and women to marry before having children.