The Catholic Church stands in direct contrast to contemporary culture on their belief in the indissolubility of marriage. While divorce is on the rise both in and out of the Church faithful, the Church is the voice in the desert arguing for the permanence of marriage, the importance of commitment and fidelity, and opposed to divorce. “[T]he marriage bond has been established by God himself in such a way that a marriage concluded and consummated between baptized persons can never by dissolved.” Marriage is grounded not in the emotionalism of the couple, not in romantic love, but rather in a conscious decision and consent at the wedding ceremony. Marriage is once and for all. The Churches teaching come directly from the words of Christ. Jesus was asked whether it was lawful to divorce for any reason. He replied:
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? So they are no longer two, but one flesh. Therefore, what God has joined together, no human being must separate…. I say to you, whoever divorces His wife (unless the marriage is unlawful) and marries another commits adultery. (Matthew 19: 4-10)
Even if a couple were to divorce civilly this does not nullify the marriage bond established under God. The Sacrament of Matrimony cannot be dissolved by humans (apart from death), but rather if truly ratified and consummated is permanent. If a couple is to divorce and get remarried without an annulment granted by the Church then the spouse who remarried is living in adultery. There, then, is no such thing as divorce and if there were, there would be no such thing as love. Love, true love, demands unity, totality, and uncompromising faithfulness. “Marriage,” writes Christopher West “by its very nature demands faithfulness of heart, mind, and action to your one and only spouse. If bride and groom don’t commit themselves to such fidelity, they are not committing to marriage.” This is very important as well in understanding Christ and His Church who will “never leave us nor forsake us.” Marriage as a sign does injury to the “covenant of salvation”.
Just as the Lord Jesus is the “faithful witness”…and the supreme realization of the unconditional faithfulness with which God loves His people, so Christian couples are called to participate truly in the irrevocable indissolubility that binds Christ to the Church, His bride, loved by him to the end.
He wills and communicates the indissolubility of marriage as a fruit, a sign and a requirement of the absolutely faithful love that God has for man and that the Lord Jesus has for the Church. The Catechism of the Catholic Church comments on this sign, “Through the Sacrament of Matrimony the spouses are enabled to represent this fidelity [that of Christ to His Church] and witness to it.” Pope John Paul II comments on the symbolism of fidelity in the life of the couple:
The gift of the sacrament is at the same time a vocation and commandment for the Christian spouses, that they may remain faithful to each other forever, beyond every trial and difficulty, in generous obedience to the holy will of the Lord: ‘What therefore God has joined together, let not man put asunder.’
To bear witness to the inestimable value of the indissolubility and fidelity of marriage is one of the most precious and most urgent tasks of Christian couples in our time….Thus in a humble and courageous manner they perform the role committed to them of being in the world a ‘sign’—a small and precious sign, sometimes also subject to temptation, but always renewed—of the unfailing fidelity with which God and Jesus Christ love each and every human being.
In order to foster healthy marriages fidelity must be a focus for preparation of the couple as well as society as a whole. Teaching children at a young age the need for commitment, being men and women who fulfill obligations, sticking when the going gets tough, will encourage them at a older age to be faithful to their marriage vows. “As a mutual gift of two persons, this intimate union, as well as the good of children, imposes total fidelity on the spouses and argues for an unbreakable oneness between them.” The couple takes a vow of indissolubility and fidelity of and to their marriage. Indissolubility is the state of marriage whereas fidelity is the personal requirement of each spouse. Fidelity is day to day with each learning and growing more in fidelity to their spouse and in so doing to God. Fidelity is not just refraining from adultery. More positively it is being faithful to the “promises made at the altar.” Tertullian describes the beauty of a faithful marriage united in spirit, “How wonderful the bond between two believers, now one in hope, one in desire, one in discipline, one in the same service! They are both children of one Father and servants of the same Master, undivided in spirit and flesh, truly two in one flesh. Where the flesh is one, one also is the spirit.”
Marriage is guaranteed by “God’s fidelity.” The marital couple also receive grace proper to the Sacrament of Matrimony that helps the “couple’s love and to strengthen their indissoluble unity.” This unity is achieved through their mutual giving and sacrifice.
“Conjugal love involves a totality, in which all the elements of the person enter—appeal of the body and instinct, power of feeling and affectivity, aspiration of the spirit and of will. It aims at a deeply personal unity, a unity that, beyond union in one flesh, leads to forming one heart and soul; it demands indissolubility and faithfulness in definitive mutual giving.” 
PLEASE NOTE: While the majority of this post is focused on preparing couples for marriage and thus the needed emphasis on the indissolubility of marriage, I would like to end by acknowledging those that find themselves divorced in the Catholic Church. The Catholic Church must be a place of healing for those separated or divorced. To often, someone who has not remarried, does not know that they CAN receive communion. It is only those who have not received an annulment and who are remarried that are unable to receive communion. And just because you are unable to receive communion does not mean you are not welcome at mass and to be active in the community.
I would encourage Catholic parishes to begin providing divorce recovery groups and to make sure we are actively reaching out to those that find themselves in these circumstances. To that end, I would recommend Ascension Press Catholic Divorce Survival Guide which can be found here: http://www.catholicsdivorce.com. It is a great program, faithful to Church teaching, and well worth the investment on the part of parishes and dioceses. The website also has resources for the divorced. So, whether you are personally divorced or ministering to the divorced, I would encourage you to go to the website.
 CCC, 1640.
 CCC, 2382.
 CCC, 1644.
 CCC, 2384.
 Pope John Paul II, Faithful to Each Other Forever, pg. 130.
 CCC, 1647.
 Faithful to Each Other Forever, pg. 130.
 Pope, 17.
 West, 108-109.
 CCC, 1642. Tertullian, Ad uxorem. 2, 8, 6-7: Pl 1, 1412-1413; cf. FC 13.
 CCC, 1640.
 CCC, 1641.
 CCC, 1643.