The Catholic theology of marriage stems from the idea that free and mutual consent of a man and a woman makes a valid marriage. Marriage, validly contracted, is a lifelong covenant that cannot be broken. A marriage can be either non-sacramental or sacramental.
Marriage between an unbaptized man and woman is presumed to be valid. Though the Catholic Church does not consider these marriages to be sacraments, they are still considered to be lifelong covenants until proven otherwise. Therefore, an unbaptized, divorced person wishing to remarry in the Catholic Church must petition for an annulment. For example: a Hindu man marries a Jewish woman, and they later divorce. The Hindu man then meets and becomes engaged to a Catholic, single woman. If they wish to marry in the Church, the Hindu man must petition for an annulment for his first marriage, because it was considered valid in the eyes of the Catholic Church.
Sacramental marriage is described as a partnership of the whole of life, ordered by its very nature to the good of the spouses and the procreation and education of children (CCC 1601). The Catholic Church teaches that sacramental marriages involve two simple principles: first (as with valid marriages), the consent of the couple makes the marriage covenant. The parties themselves are the “ministers of the sacrament” to each other. This is based on the exercise of their “priestly ministry”, which was conferred on them at Baptism. The second principle states that the marriage of two validly baptized persons is automatically a sacrament in the eyes of God and the Church (CCC 2360). Accordingly, a sacramental marriage is not only presumed for two Catholics; the marriage of two baptized Presbyterians, Lutherans, Baptists or other denominations is also considered a sacrament.