For centuries men and women have repeated the vow, "till death do us part", feeling that they express the natural resolve of two people who are so in love as to get married. The Catholic Church continues to take these words seriously; and sees them as corresponding to the fact that marriage is naturally meant to be an indissoluble union. She continues to teach the indissolubility of the marriage bond, not as a law of the Church applying just to the marriage of Catholics, but as a law of God for all marriages.
A man and a woman marry because they are in love and want to share life together. They choose one another in preference to all possible others, because they think they will be happier with the other than with anyone else. In many cases it works: but not always. People gradually run into difficulties, discover each other's defects, get irritated, have small quarrels and then bigger ones, feel attracted to someone else... Love and fidelity often survive the crisis, and take on a more voluntary and mature form. The couple "make it". Other couples do not; love declines and finally "dies". Then the idea of continuing in a loveless marriage appears senseless.
The Catechism of the Catholic Church (no. 1633) insists on the difficulties which can arise in the case of mixed marriages (between a Catholic and a baptized non-Catholic), and even more so when there is disparity of cult (a marriage between a Catholic and a non-baptized person). The Catechism goes on (1634): "Differences about faith and the very notion of marriage, but also different religious mentalities, can become sources of tension in marriage, especially as regards the education of children. The temptation to religious indifference can then arise" - especially among the children, who will have to grow up in a secularized world without the support that comes from a home united in faith.
"Married personalism" (the debate on this site between Professor Rik Torfs of Louvain and myself) has provoked quite a number of email comments from readers. While Prof Torfs and I are very good friends, our views on the topic of Married Personalism are quite different; which of course is why we could debate. It might be helpful if I here attempt a very brief summary of my views on two points in particular: married personalism and the good of the spouses.