The Catholic Church teaches that marriage is, by God’s plan, a covenant between a man and a woman in which they establish an intimate, exclusive and permanent partnership of the whole of life, which exists for the good of the spouses, for the giving and receiving of love, and for the procreation and education of children. Marriage is brought into being by the mutual, voluntary, and deliberate exchange of consent (marriage vows) of the two parties—legitimately manifested between persons who are capable, according to Church law, of giving consent.
In unions where both parties are baptized, a valid marriage is also a sacrament. The Catholic Church has consistently taught that every valid, sacramental marriage which has been consummated is indissoluble. Although not every marriage is sacramental, every marriage (Catholic, Protestant, Jewish, non-believer, etc.) between those who are free to marry is presumed to be valid. This presumption is the case for every marriage, regardless of whether the parties are Catholic or not. The good of all concerned (spouses, children, family, society, the Church, etc.) demands this presumption.
While the Catholic Church upholds the dignity, sacredness, and permanence of marriage, it cannot ignore the reality of separation and divorce in our society. The Church must reach out to those who are struggling with the pain of a broken marriage.
Yet, even though the Church presumes that every marriage is valid, the opposite may be true. If sufficient evidence can be shown that an impediment to marriage existed, if an essential element was lacking or so gravely flawed, if the consent between the parties was defective in any way, or if there existed some defect of the proper canonical form of marriage, the validity of the marriage may be questioned. This declaration of nullity (invalidity) by the Catholic Church is commonly referred to as a marriage “annulment.”