A marriage is a (1) lifelong community (2) of exactly one man and exactly one woman, (3) which is based on mutual, mutually guaranteed love, fidelity and conjugal honesty, (4) and targeted (aligned) towards procreation and (5) raising and educating of children. Here (6) sharing of accommodation and time (7) and precedence of this community over all other human relationships of the spouses is required. Spouses together with their children form the basic unit of society, called the family. Marriage is the core of the family.
Please pay attention to the item (4) - procreation of a child means that a child is a child already at conception and not only after birth. (This is the understanding of the Polish constitution, when it talks about Polish citizens - one is a Polish citizen since conception). The point (4) implies (2) and exacts immediately (1), (3), (5), (6) and (7). If after the occurrence of the facts (4) the other points are completely or partially not met, serious social disorder follows.
The mutual fulfillment of the point (3) is expected by both husband and wife. But also the society hopes that the married couples stick to it. The reason lies in biology: because of potential genetic problems a marriage between close relatives must be excluded. It is therefore necessary that the kinship can be detected or ruled out easily.
Immediate exaction means that the marriage can not be a process, but must be completed in a single step. All attributes of marriage must occur immediately, they must be in power at the same time. There is no "trial marriage", handfasting is not acceptable.
Therefore, it is a long tradition of holding wedding ceremonies that constitute a solemn framework of getting married.
A church wedding is an extraordinary offer under the variety of such ceremonies. It is in fact an act of sacramental marriage. A sacrament of matrimony is a unique convenant in which the future spouses commit themselves to fulfill the complete package of the above conditions.
Sacramental marriage is accomplished when a man and a woman swear each other: "I (name) take you (name) to my wife (my husband) and I vow you love, fidelity and conjugal honesty, and that I will not leave you untill death. So help me Lord, God the Almighty Trinity and all the Saints." After the the mutual love oath of the couple the priest explains: "What God has joined together, let not man put asunder. By the authority of the Church I ratify and bless the bond of marriage you have contracted. In the name of the Father and of the Son and of the Holy Spirit. Amen. "
In what way does a sacramental marriage differ from civil or natural marriage?
For thousands of years, it has been clear to people that the the conditions (1) - (7) must be satisfied by the institution of marriage. But it is just as clearly seen that it is not an easy task. As once Lord Jesus was asked about the divorce, he replied: "Have you not read in the Scripture, that God who made man from the beginning, made them male and female? And he said: For this cause shall a man leave father and mother, and shall cleave to his wife, and they two shall be in one flesh. Therefore now they are not two, but one flesh. What therefore God has joined together, let no man put asunder. And I say to you, that whosoever shall put away his wife, except it be for fornication, and shall marry another, commits adultery: and he that shall marry her that is put away, commits adultery." Then the disciples said unto him: "If the case of a man so with his wife, so it is not good to marry. "(Matthew 19: 4-10).
But Lord Jesus tells us: "Everything is possible with God" (Matthew 19:26) and "Everything is possible for him who believes" (Mark 9:24). Therefore spouses, wanting to make marital vow, seek help and the priest gives them the divine blessing. Moreover, through his hands, the sanctifying grace of God flows to the couple during the sacramental ceremony. Thus equipped, they are able to face the challenges of married life and to overcome all difficulties.
Christ strengthens their love with his love, that he grants the Church. Christ is on the side of the newlyweds and by his Spirit makes them perfect, so that their human love is constantly evolving and overcomes all trials, so that they can fulfill their new obligations ie arrange the marital and familial life properly, so that they create a proper climate that is necessary for good raising and education of children. (See http://www.teologia.pl/m_k/zag06-7b.htm#4)
The value of the grace of God is not just a hypothesis of theologians but also experimentally verified scientific finding. When both spouses pray together every day and go every Sunday to church, plus choose a life of abstinence from alcohol, then the risk of divorce 2,000 times lower than that of civil marriages and 100,000 times lower than that of "informal relations". From this we see that science and faith lead to the same conclusions: All you shall rely on God. In this context one should remember the decision of the Polish Bishops' Conference of 06.17.1959, which states inter alia: "The bishops also demand that the receptions of the faithful will organize on the occasion of [...] family celebrations without alcohol. In case of non-alcoholic wedding the local bishop will send a special episcopal blessing for the newlyweds. " (See the lecture by Dr. M.Guzewicz during the wedding of weddings in 2007 in Bydgoszcz).
For men and women, that are "inclined to each other", the church wedding is a unique offer: Full marriage and the sanctifying grace needed to maintain the marriage. Such an offer can only be found in the Catholic Church.
See also Why Nonalcoholic Wedding